[PATCHv5,3/3] i2c: altera: Add Altera I2C Controller driver

Message ID 1500309314-18464-4-git-send-email-thor.thayer@linux.intel.com
State Changes Requested
Headers show

Commit Message

Thor Thayer July 17, 2017, 4:35 p.m.
From: Thor Thayer <thor.thayer@linux.intel.com>

Add driver support for the Altera I2C Controller. The I2C
controller is soft IP for use in FPGAs.

Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>
---
v2  Remove altr, from fifo-size to agree with bindings.
    Change compatible string to "altr,softip-i2c"
v3  Add version to compatible string "altr,softip-i2c-v1.0"
v4  Add default 100kHz message. Cleanup IRQ error message.
v5  Cleanup header usage - remove init.h.
    Fix 1 byte RX bug and add convenience function for transfer shared by RX and TX.
    Use readl_poll_timeout_atomic() function.
    Cache the I2C Interrupt Status Enable Register.
    Cleanup of irq_mask by combining into 1 function.
    Use i2c_8bit_addr_from_msg() for cleaner xfer_msg implementation.
    Restructure altr_i2c_xfer() without arrays and indexes.
    Remove redundant assignments.
    Remove function calls from inside if() statements.
    Convert of_property_read_u32() to device_property_read_u32().
    Call i2c_m_read() once in irq.
---
 drivers/i2c/busses/Kconfig      |  10 +
 drivers/i2c/busses/Makefile     |   1 +
 drivers/i2c/busses/i2c-altera.c | 510 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 521 insertions(+)
 create mode 100644 drivers/i2c/busses/i2c-altera.c

Comments

Andy Shevchenko July 26, 2017, 10:37 a.m. | #1
On Mon, Jul 17, 2017 at 7:35 PM,  <thor.thayer@linux.intel.com> wrote:
> From: Thor Thayer <thor.thayer@linux.intel.com>
>
> Add driver support for the Altera I2C Controller. The I2C
> controller is soft IP for use in FPGAs.
>

So, there are few more things that can be improved, like removing
__func__ parameter from dev_printk() calls or _isr() refactoring,
though I leave it to be judged by Wolfram and others.

To avoid any further bikeshedding it looks good enough to me, FWIW,
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

> Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>
> ---
> v2  Remove altr, from fifo-size to agree with bindings.
>     Change compatible string to "altr,softip-i2c"
> v3  Add version to compatible string "altr,softip-i2c-v1.0"
> v4  Add default 100kHz message. Cleanup IRQ error message.
> v5  Cleanup header usage - remove init.h.
>     Fix 1 byte RX bug and add convenience function for transfer shared by RX and TX.
>     Use readl_poll_timeout_atomic() function.
>     Cache the I2C Interrupt Status Enable Register.
>     Cleanup of irq_mask by combining into 1 function.
>     Use i2c_8bit_addr_from_msg() for cleaner xfer_msg implementation.
>     Restructure altr_i2c_xfer() without arrays and indexes.
>     Remove redundant assignments.
>     Remove function calls from inside if() statements.
>     Convert of_property_read_u32() to device_property_read_u32().
>     Call i2c_m_read() once in irq.
> ---
>  drivers/i2c/busses/Kconfig      |  10 +
>  drivers/i2c/busses/Makefile     |   1 +
>  drivers/i2c/busses/i2c-altera.c | 510 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 521 insertions(+)
>  create mode 100644 drivers/i2c/busses/i2c-altera.c
>
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index 1006b23..668147bf 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -328,6 +328,16 @@ config I2C_POWERMAC
>
>  comment "I2C system bus drivers (mostly embedded / system-on-chip)"
>
> +config I2C_ALTERA
> +       tristate "Altera Soft IP I2C"
> +       depends on (ARCH_SOCFPGA || NIOS2) && OF
> +       help
> +         If you say yes to this option, support will be included for the
> +         Altera Soft IP I2C interfaces on SoCFPGA and Nios2 architectures.
> +
> +         This driver can also be built as a module.  If so, the module
> +         will be called i2c-altera.
> +
>  config I2C_ASPEED
>         tristate "Aspeed I2C Controller"
>         depends on ARCH_ASPEED || COMPILE_TEST
> diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> index 1b2fc81..1395dcb 100644
> --- a/drivers/i2c/busses/Makefile
> +++ b/drivers/i2c/busses/Makefile
> @@ -29,6 +29,7 @@ obj-$(CONFIG_I2C_HYDRA)               += i2c-hydra.o
>  obj-$(CONFIG_I2C_POWERMAC)     += i2c-powermac.o
>
>  # Embedded system I2C/SMBus host controller drivers
> +obj-$(CONFIG_I2C_ALTERA)       += i2c-altera.o
>  obj-$(CONFIG_I2C_ASPEED)       += i2c-aspeed.o
>  obj-$(CONFIG_I2C_AT91)         += i2c-at91.o
>  obj-$(CONFIG_I2C_AU1550)       += i2c-au1550.o
> diff --git a/drivers/i2c/busses/i2c-altera.c b/drivers/i2c/busses/i2c-altera.c
> new file mode 100644
> index 0000000..e818901
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-altera.c
> @@ -0,0 +1,510 @@
> +/*
> + *  Copyright Intel Corporation (C) 2017.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program.  If not, see <http://www.gnu.org/licenses/>.
> + *
> + * Based on the i2c-axxia.c driver.
> + */
> +#include <linux/clk.h>
> +#include <linux/clkdev.h>
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/iopoll.h>
> +#include <linux/interrupt.h>
> +#include <linux/module.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/platform_device.h>
> +
> +#define ALTR_I2C_TFR_CMD       0x00    /* Transfer Command register */
> +#define     ALTR_I2C_TFR_CMD_STA       BIT(9)  /* send START before byte */
> +#define     ALTR_I2C_TFR_CMD_STO       BIT(8)  /* send STOP after byte */
> +#define     ALTR_I2C_TFR_CMD_RW_D      BIT(0)  /* Direction of transfer */
> +#define ALTR_I2C_RX_DATA       0x04    /* RX data FIFO register */
> +#define ALTR_I2C_CTRL          0x08    /* Control register */
> +#define     ALTR_I2C_CTRL_RXT_SHFT     4       /* RX FIFO Threshold */
> +#define     ALTR_I2C_CTRL_TCT_SHFT     2       /* TFER CMD FIFO Threshold */
> +#define     ALTR_I2C_CTRL_BSPEED       BIT(1)  /* Bus Speed (1=Fast) */
> +#define     ALTR_I2C_CTRL_EN   BIT(0)  /* Enable Core (1=Enable) */
> +#define ALTR_I2C_ISER          0x0C    /* Interrupt Status Enable register */
> +#define     ALTR_I2C_ISER_RXOF_EN      BIT(4)  /* Enable RX OVERFLOW IRQ */
> +#define     ALTR_I2C_ISER_ARB_EN       BIT(3)  /* Enable ARB LOST IRQ */
> +#define     ALTR_I2C_ISER_NACK_EN      BIT(2)  /* Enable NACK DET IRQ */
> +#define     ALTR_I2C_ISER_RXRDY_EN     BIT(1)  /* Enable RX Ready IRQ */
> +#define     ALTR_I2C_ISER_TXRDY_EN     BIT(0)  /* Enable TX Ready IRQ */
> +#define ALTR_I2C_ISR           0x10    /* Interrupt Status register */
> +#define     ALTR_I2C_ISR_RXOF          BIT(4)  /* RX OVERFLOW IRQ */
> +#define     ALTR_I2C_ISR_ARB           BIT(3)  /* ARB LOST IRQ */
> +#define     ALTR_I2C_ISR_NACK          BIT(2)  /* NACK DET IRQ */
> +#define     ALTR_I2C_ISR_RXRDY         BIT(1)  /* RX Ready IRQ */
> +#define     ALTR_I2C_ISR_TXRDY         BIT(0)  /* TX Ready IRQ */
> +#define ALTR_I2C_STATUS                0x14    /* Status register */
> +#define     ALTR_I2C_STAT_CORE         BIT(0)  /* Core Status (0=idle) */
> +#define ALTR_I2C_TC_FIFO_LVL   0x18    /* Transfer FIFO LVL register */
> +#define ALTR_I2C_RX_FIFO_LVL   0x1C    /* Receive FIFO LVL register */
> +#define ALTR_I2C_SCL_LOW       0x20    /* SCL low count register */
> +#define ALTR_I2C_SCL_HIGH      0x24    /* SCL high count register */
> +#define ALTR_I2C_SDA_HOLD      0x28    /* SDA hold count register */
> +
> +#define ALTR_I2C_ALL_IRQ       (ALTR_I2C_ISR_RXOF | ALTR_I2C_ISR_ARB | \
> +                                ALTR_I2C_ISR_NACK | ALTR_I2C_ISR_RXRDY | \
> +                                ALTR_I2C_ISR_TXRDY)
> +
> +#define ALTR_I2C_THRESHOLD     0       /* IRQ Threshold at 1 element */
> +#define ALTR_I2C_DFLT_FIFO_SZ  4
> +#define ALTR_I2C_TIMEOUT       100000  /* 100ms */
> +#define ALTR_I2C_XFER_TIMEOUT  (msecs_to_jiffies(250))
> +
> +/**
> + * altr_i2c_dev - I2C device context
> + * @base: pointer to register struct
> + * @msg: pointer to current message
> + * @msg_len: number of bytes transferred in msg
> + * @msg_err: error code for completed message
> + * @msg_complete: xfer completion object
> + * @dev: device reference
> + * @adapter: core i2c abstraction
> + * @i2c_clk: clock reference for i2c input clock
> + * @bus_clk_rate: current i2c bus clock rate
> + * @buf: ptr to msg buffer for easier use.
> + * @fifo_size: size of the FIFO passed in.
> + */
> +struct altr_i2c_dev {
> +       void __iomem *base;
> +       struct i2c_msg *msg;
> +       size_t msg_len;
> +       int msg_err;
> +       struct completion msg_complete;
> +       struct device *dev;
> +       struct i2c_adapter adapter;
> +       struct clk *i2c_clk;
> +       u32 bus_clk_rate;
> +       u8 *buf;
> +       u32 fifo_size;
> +       u32 isr_mask;
> +};
> +
> +static void i2c_int_enable(struct altr_i2c_dev *idev, u32 mask, bool enable)
> +{
> +       u32 int_en = readl(idev->base + ALTR_I2C_ISER);
> +
> +       if (enable)
> +               idev->isr_mask = int_en | mask;
> +       else
> +               idev->isr_mask = int_en & ~mask;
> +
> +       writel(idev->isr_mask, idev->base + ALTR_I2C_ISER);
> +}
> +
> +static void i2c_int_clear(struct altr_i2c_dev *idev, u32 mask)
> +{
> +       u32 int_en = readl(idev->base + ALTR_I2C_ISR);
> +
> +       writel(int_en | mask, idev->base + ALTR_I2C_ISR);
> +}
> +
> +static void altr_i2c_core_disable(struct altr_i2c_dev *idev)
> +{
> +       u32 tmp = readl(idev->base + ALTR_I2C_CTRL);
> +
> +       writel(tmp & ~ALTR_I2C_CTRL_EN, idev->base + ALTR_I2C_CTRL);
> +}
> +
> +static void altr_i2c_core_enable(struct altr_i2c_dev *idev)
> +{
> +       u32 tmp = readl(idev->base + ALTR_I2C_CTRL);
> +
> +       writel(tmp | ALTR_I2C_CTRL_EN, idev->base + ALTR_I2C_CTRL);
> +}
> +
> +static void altr_i2c_reset(struct altr_i2c_dev *idev)
> +{
> +       altr_i2c_core_disable(idev);
> +       altr_i2c_core_enable(idev);
> +}
> +
> +static void altr_i2c_recover(struct altr_i2c_dev *idev)
> +{
> +       altr_i2c_reset(idev);
> +       /* Clock start bit + 8 bits + stop bit out */
> +       writel(ALTR_I2C_TFR_CMD_STA | ALTR_I2C_TFR_CMD_STO,
> +              idev->base + ALTR_I2C_TFR_CMD);
> +       altr_i2c_reset(idev);
> +
> +       i2c_recover_bus(&idev->adapter);
> +}
> +
> +static inline void altr_i2c_stop(struct altr_i2c_dev *idev)
> +{
> +       writel(ALTR_I2C_TFR_CMD_STO, idev->base + ALTR_I2C_TFR_CMD);
> +}
> +
> +static void altr_i2c_init(struct altr_i2c_dev *idev)
> +{
> +       u32 divisor = clk_get_rate(idev->i2c_clk) / idev->bus_clk_rate;
> +       u32 clk_mhz = clk_get_rate(idev->i2c_clk) / 1000000;
> +       u32 tmp = (ALTR_I2C_THRESHOLD << ALTR_I2C_CTRL_RXT_SHFT) |
> +                 (ALTR_I2C_THRESHOLD << ALTR_I2C_CTRL_TCT_SHFT);
> +       u32 t_high, t_low;
> +
> +       if (idev->bus_clk_rate <= 100000) {
> +               tmp &= ~ALTR_I2C_CTRL_BSPEED;
> +               /* Standard mode SCL 50/50 */
> +               t_high = divisor * 1 / 2;
> +               t_low = divisor * 1 / 2;
> +       } else {
> +               tmp |= ALTR_I2C_CTRL_BSPEED;
> +               /* Fast mode SCL 33/66 */
> +               t_high = divisor * 1 / 3;
> +               t_low = divisor * 2 / 3;
> +       }
> +       writel(tmp, idev->base + ALTR_I2C_CTRL);
> +
> +       dev_dbg(idev->dev, "rate=%uHz per_clk=%uMHz -> ratio=1:%u\n",
> +               idev->bus_clk_rate, clk_mhz, divisor);
> +
> +       /* Reset controller */
> +       altr_i2c_reset(idev);
> +
> +       /* SCL High Time */
> +       writel(t_high, idev->base + ALTR_I2C_SCL_HIGH);
> +       /* SCL Low Time */
> +       writel(t_low, idev->base + ALTR_I2C_SCL_LOW);
> +       /* SDA Hold Time, 300ns */
> +       writel(div_u64(300 * clk_mhz, 1000), idev->base + ALTR_I2C_SDA_HOLD);
> +
> +       /* Mask all master interrupt bits */
> +       i2c_int_enable(idev, ALTR_I2C_ALL_IRQ, false);
> +}
> +
> +static int i2c_m_rd(const struct i2c_msg *msg)
> +{
> +       return (msg->flags & I2C_M_RD) != 0;
> +}
> +
> +/**
> + * altr_i2c_transfer - On the last byte to be transmitted, send
> + * a Stop bit on the last byte.
> + */
> +static void altr_i2c_transfer(struct altr_i2c_dev *idev, u32 data)
> +{
> +       /* On the last byte to be transmitted, send STOP */
> +       if (idev->msg_len == 1)
> +               data |= ALTR_I2C_TFR_CMD_STO;
> +       if (idev->msg_len > 0)
> +               writel(data, idev->base + ALTR_I2C_TFR_CMD);
> +}
> +
> +/**
> + * altr_i2c_empty_rx_fifo - Fetch data from RX FIFO until end of
> + * transfer. Send a Stop bit on the last byte.
> + */
> +static void altr_i2c_empty_rx_fifo(struct altr_i2c_dev *idev)
> +{
> +       size_t rx_fifo_avail = readl(idev->base + ALTR_I2C_RX_FIFO_LVL);
> +       int bytes_to_transfer = min(rx_fifo_avail, idev->msg_len);
> +
> +       while (bytes_to_transfer-- > 0) {
> +               *idev->buf++ = readl(idev->base + ALTR_I2C_RX_DATA);
> +               idev->msg_len--;
> +               altr_i2c_transfer(idev, 0);
> +       }
> +}
> +
> +/**
> + * altr_i2c_fill_tx_fifo - Fill TX FIFO from current message buffer.
> + * @return: Number of bytes left to transfer.
> + */
> +static int altr_i2c_fill_tx_fifo(struct altr_i2c_dev *idev)
> +{
> +       size_t tx_fifo_avail = idev->fifo_size - readl(idev->base +
> +                                                      ALTR_I2C_TC_FIFO_LVL);
> +       int bytes_to_transfer = min(tx_fifo_avail, idev->msg_len);
> +       int ret = idev->msg_len - bytes_to_transfer;
> +
> +       while (bytes_to_transfer-- > 0) {
> +               altr_i2c_transfer(idev, *idev->buf++);
> +               idev->msg_len--;
> +       }
> +
> +       return ret;
> +}
> +
> +static irqreturn_t altr_i2c_isr(int irq, void *_dev)
> +{
> +       int ret, read;
> +       struct altr_i2c_dev *idev = _dev;
> +       /* Read IRQ status but only interested in Enabled IRQs. */
> +       u32 status = readl(idev->base + ALTR_I2C_ISR) & idev->isr_mask;
> +
> +       if (!idev->msg) {
> +               dev_warn(idev->dev, "unexpected interrupt\n");
> +               goto out;
> +       }
> +       read = i2c_m_rd(idev->msg);
> +
> +       /* handle Lost Arbitration */
> +       if (unlikely(status & ALTR_I2C_ISR_ARB)) {
> +               dev_err(idev->dev, "%s: arbitration lost\n", __func__);
> +               i2c_int_clear(idev, ALTR_I2C_ISR_ARB);
> +               idev->msg_err = -EAGAIN;
> +               goto complete;
> +       }
> +
> +       if (unlikely(status & ALTR_I2C_ISR_NACK)) {
> +               dev_dbg(idev->dev, "%s: could not get ACK\n", __func__);
> +               idev->msg_err = -ENXIO;
> +               i2c_int_clear(idev, ALTR_I2C_ISR_NACK);
> +               altr_i2c_stop(idev);
> +               goto complete;
> +       }
> +
> +       /* handle RX FIFO Overflow */
> +       if (read && unlikely(status & ALTR_I2C_ISR_RXOF)) {
> +               altr_i2c_empty_rx_fifo(idev);
> +               i2c_int_clear(idev, ALTR_I2C_ISR_RXRDY);
> +               altr_i2c_stop(idev);
> +               dev_err(idev->dev, "%s: RX FIFO Overflow\n", __func__);
> +               goto complete;
> +       }
> +
> +       /* RX FIFO needs service? */
> +       if (read && (status & ALTR_I2C_ISR_RXRDY)) {
> +               altr_i2c_empty_rx_fifo(idev);
> +               i2c_int_clear(idev, ALTR_I2C_ISR_RXRDY);
> +               if (!idev->msg_len)
> +                       goto complete;
> +
> +               goto out;
> +       }
> +
> +       /* TX FIFO needs service? */
> +       if (!read && (status & ALTR_I2C_ISR_TXRDY)) {
> +               i2c_int_clear(idev, ALTR_I2C_ISR_TXRDY);
> +               if (!altr_i2c_fill_tx_fifo(idev))
> +                       goto complete;
> +
> +               goto out;
> +       }
> +
> +complete:
> +       /* Wait for the Core to finish */
> +       ret = readl_poll_timeout_atomic(idev->base + ALTR_I2C_STATUS, status,
> +                                       ((status & ALTR_I2C_STAT_CORE) == 0),
> +                                       1, ALTR_I2C_TIMEOUT);
> +       if (ret)
> +               dev_err(idev->dev, "%s: message timeout\n", __func__);
> +       i2c_int_enable(idev, ALTR_I2C_ALL_IRQ, false);
> +       i2c_int_clear(idev, ALTR_I2C_ALL_IRQ);
> +       complete(&idev->msg_complete);
> +       dev_dbg(idev->dev, "%s: Message Complete\n", __func__);
> +
> +out:
> +       return IRQ_HANDLED;
> +}
> +
> +static int altr_i2c_xfer_msg(struct altr_i2c_dev *idev, struct i2c_msg *msg)
> +{
> +       u32 imask = ALTR_I2C_ISR_RXOF | ALTR_I2C_ISR_ARB | ALTR_I2C_ISR_NACK;
> +       unsigned long time_left;
> +       u32 value;
> +       u8 addr = i2c_8bit_addr_from_msg(msg);
> +
> +       idev->msg = msg;
> +       idev->msg_len = msg->len;
> +       idev->buf = msg->buf;
> +       idev->msg_err = 0;
> +       reinit_completion(&idev->msg_complete);
> +       altr_i2c_core_enable(idev);
> +
> +       /* Make sure RX FIFO is empty */
> +       do {
> +               readl(idev->base + ALTR_I2C_RX_DATA);
> +       } while (readl(idev->base + ALTR_I2C_RX_FIFO_LVL));
> +
> +       writel(ALTR_I2C_TFR_CMD_STA | addr, idev->base + ALTR_I2C_TFR_CMD);
> +
> +       if (i2c_m_rd(msg)) {
> +               imask |= ALTR_I2C_ISER_RXOF_EN | ALTR_I2C_ISER_RXRDY_EN;
> +               i2c_int_enable(idev, imask, true);
> +               /* write the first byte to start the RX */
> +               altr_i2c_transfer(idev, 0);
> +       } else {
> +               imask |= ALTR_I2C_ISR_TXRDY;
> +               i2c_int_enable(idev, imask, true);
> +               altr_i2c_fill_tx_fifo(idev);
> +       }
> +
> +       time_left = wait_for_completion_timeout(&idev->msg_complete,
> +                                               ALTR_I2C_XFER_TIMEOUT);
> +       i2c_int_enable(idev, imask, false);
> +
> +       value = readl(idev->base + ALTR_I2C_STATUS) & ALTR_I2C_STAT_CORE;
> +       if (value)
> +               dev_err(idev->dev, "%s: Core Status not IDLE...\n", __func__);
> +
> +       if (time_left == 0) {
> +               idev->msg_err = -ETIMEDOUT;
> +               dev_err(idev->dev, "%s: Transaction timed out.\n", __func__);
> +               altr_i2c_recover(idev);
> +       }
> +
> +       if (unlikely(idev->msg_err) && idev->msg_err != -ENXIO)
> +               altr_i2c_init(idev);
> +
> +       altr_i2c_core_disable(idev);
> +
> +       return idev->msg_err;
> +}
> +
> +static int
> +altr_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
> +{
> +       struct altr_i2c_dev *idev = i2c_get_adapdata(adap);
> +       int i, ret;
> +
> +       for (i = 0; i < num; i++) {
> +               ret = altr_i2c_xfer_msg(idev, msgs++);
> +               if (ret)
> +                       return ret;
> +       }
> +       return num;
> +}
> +
> +static u32 altr_i2c_func(struct i2c_adapter *adap)
> +{
> +       return I2C_FUNC_I2C;
> +}
> +
> +static const struct i2c_algorithm altr_i2c_algo = {
> +       .master_xfer = altr_i2c_xfer,
> +       .functionality = altr_i2c_func,
> +};
> +
> +static int altr_i2c_probe(struct platform_device *pdev)
> +{
> +       struct altr_i2c_dev *idev = NULL;
> +       struct resource *res;
> +       int irq, ret;
> +       u32 val;
> +
> +       idev = devm_kzalloc(&pdev->dev, sizeof(*idev), GFP_KERNEL);
> +       if (!idev)
> +               return -ENOMEM;
> +
> +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +       idev->base = devm_ioremap_resource(&pdev->dev, res);
> +       if (IS_ERR(idev->base))
> +               return PTR_ERR(idev->base);
> +
> +       irq = platform_get_irq(pdev, 0);
> +       if (irq < 0) {
> +               dev_err(&pdev->dev, "missing interrupt resource\n");
> +               return irq;
> +       }
> +
> +       idev->i2c_clk = devm_clk_get(&pdev->dev, NULL);
> +       if (IS_ERR(idev->i2c_clk)) {
> +               dev_err(&pdev->dev, "missing clock\n");
> +               return PTR_ERR(idev->i2c_clk);
> +       }
> +
> +       idev->dev = &pdev->dev;
> +       init_completion(&idev->msg_complete);
> +
> +       val = device_property_read_u32(idev->dev, "fifo-size",
> +                                      &idev->fifo_size);
> +       if (val) {
> +               dev_err(&pdev->dev, "FIFO size set to default of %d\n",
> +                       ALTR_I2C_DFLT_FIFO_SZ);
> +               idev->fifo_size = ALTR_I2C_DFLT_FIFO_SZ;
> +       }
> +
> +       val = device_property_read_u32(idev->dev, "clock-frequency",
> +                                      &idev->bus_clk_rate);
> +       if (val) {
> +               dev_err(&pdev->dev, "Default to 100kHz\n");
> +               idev->bus_clk_rate = 100000;    /* default clock rate */
> +       }
> +
> +       if (idev->bus_clk_rate > 400000) {
> +               dev_err(&pdev->dev, "invalid clock-frequency %d\n",
> +                       idev->bus_clk_rate);
> +               return -EINVAL;
> +       }
> +
> +       ret = devm_request_irq(&pdev->dev, irq, altr_i2c_isr, 0,
> +                              pdev->name, idev);
> +       if (ret) {
> +               dev_err(&pdev->dev, "failed to claim IRQ %d\n", irq);
> +               return ret;
> +       }
> +
> +       ret = clk_prepare_enable(idev->i2c_clk);
> +       if (ret) {
> +               dev_err(&pdev->dev, "failed to enable clock\n");
> +               return ret;
> +       }
> +
> +       altr_i2c_init(idev);
> +
> +       i2c_set_adapdata(&idev->adapter, idev);
> +       strlcpy(idev->adapter.name, pdev->name, sizeof(idev->adapter.name));
> +       idev->adapter.owner = THIS_MODULE;
> +       idev->adapter.algo = &altr_i2c_algo;
> +       idev->adapter.dev.parent = &pdev->dev;
> +       idev->adapter.dev.of_node = pdev->dev.of_node;
> +
> +       platform_set_drvdata(pdev, idev);
> +
> +       ret = i2c_add_adapter(&idev->adapter);
> +       if (ret) {
> +               clk_disable_unprepare(idev->i2c_clk);
> +               return ret;
> +       }
> +       dev_info(&pdev->dev, "Altera SoftIP I2C Probe Complete\n");
> +
> +       return 0;
> +}
> +
> +static int altr_i2c_remove(struct platform_device *pdev)
> +{
> +       struct altr_i2c_dev *idev = platform_get_drvdata(pdev);
> +
> +       clk_disable_unprepare(idev->i2c_clk);
> +       i2c_del_adapter(&idev->adapter);
> +
> +       return 0;
> +}
> +
> +/* Match table for of_platform binding */
> +static const struct of_device_id altr_i2c_of_match[] = {
> +       { .compatible = "altr,softip-i2c-v1.0" },
> +       {},
> +};
> +MODULE_DEVICE_TABLE(of, altr_i2c_of_match);
> +
> +static struct platform_driver altr_i2c_driver = {
> +       .probe = altr_i2c_probe,
> +       .remove = altr_i2c_remove,
> +       .driver = {
> +               .name = "altera-i2c",
> +               .of_match_table = altr_i2c_of_match,
> +       },
> +};
> +
> +module_platform_driver(altr_i2c_driver);
> +
> +MODULE_DESCRIPTION("Altera Soft IP I2C bus driver");
> +MODULE_AUTHOR("Thor Thayer <thor.thayer@linux.intel.com>");
> +MODULE_LICENSE("GPL v2");
> --
> 2.7.4
>
Wolfram Sang July 31, 2017, 1:31 p.m. | #2
Hi Thor,

thanks for the patches! A few comments and questions from me.

On Mon, Jul 17, 2017 at 11:35:14AM -0500, thor.thayer@linux.intel.com wrote:
> From: Thor Thayer <thor.thayer@linux.intel.com>
> 
> Add driver support for the Altera I2C Controller. The I2C
> controller is soft IP for use in FPGAs.
> 
> Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>
> ---
> v2  Remove altr, from fifo-size to agree with bindings.
>     Change compatible string to "altr,softip-i2c"
> v3  Add version to compatible string "altr,softip-i2c-v1.0"
> v4  Add default 100kHz message. Cleanup IRQ error message.
> v5  Cleanup header usage - remove init.h.
>     Fix 1 byte RX bug and add convenience function for transfer shared by RX and TX.
>     Use readl_poll_timeout_atomic() function.
>     Cache the I2C Interrupt Status Enable Register.
>     Cleanup of irq_mask by combining into 1 function.
>     Use i2c_8bit_addr_from_msg() for cleaner xfer_msg implementation.
>     Restructure altr_i2c_xfer() without arrays and indexes.
>     Remove redundant assignments.
>     Remove function calls from inside if() statements.
>     Convert of_property_read_u32() to device_property_read_u32().
>     Call i2c_m_read() once in irq.
> ---
>  drivers/i2c/busses/Kconfig      |  10 +
>  drivers/i2c/busses/Makefile     |   1 +
>  drivers/i2c/busses/i2c-altera.c | 510 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 521 insertions(+)
>  create mode 100644 drivers/i2c/busses/i2c-altera.c
> 
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index 1006b23..668147bf 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -328,6 +328,16 @@ config I2C_POWERMAC
>  
>  comment "I2C system bus drivers (mostly embedded / system-on-chip)"
>  
> +config I2C_ALTERA
> +	tristate "Altera Soft IP I2C"
> +	depends on (ARCH_SOCFPGA || NIOS2) && OF
> +	help
> +	  If you say yes to this option, support will be included for the
> +	  Altera Soft IP I2C interfaces on SoCFPGA and Nios2 architectures.
> +
> +	  This driver can also be built as a module.  If so, the module
> +	  will be called i2c-altera.
> +
>  config I2C_ASPEED
>  	tristate "Aspeed I2C Controller"
>  	depends on ARCH_ASPEED || COMPILE_TEST
> diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> index 1b2fc81..1395dcb 100644
> --- a/drivers/i2c/busses/Makefile
> +++ b/drivers/i2c/busses/Makefile
> @@ -29,6 +29,7 @@ obj-$(CONFIG_I2C_HYDRA)		+= i2c-hydra.o
>  obj-$(CONFIG_I2C_POWERMAC)	+= i2c-powermac.o
>  
>  # Embedded system I2C/SMBus host controller drivers
> +obj-$(CONFIG_I2C_ALTERA)	+= i2c-altera.o
>  obj-$(CONFIG_I2C_ASPEED)	+= i2c-aspeed.o
>  obj-$(CONFIG_I2C_AT91)		+= i2c-at91.o
>  obj-$(CONFIG_I2C_AU1550)	+= i2c-au1550.o
> diff --git a/drivers/i2c/busses/i2c-altera.c b/drivers/i2c/busses/i2c-altera.c
> new file mode 100644
> index 0000000..e818901
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-altera.c
> @@ -0,0 +1,510 @@
> +/*
> + *  Copyright Intel Corporation (C) 2017.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program.  If not, see <http://www.gnu.org/licenses/>.
> + *
> + * Based on the i2c-axxia.c driver.
> + */
> +#include <linux/clk.h>
> +#include <linux/clkdev.h>
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/iopoll.h>
> +#include <linux/interrupt.h>
> +#include <linux/module.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/platform_device.h>
> +
> +#define ALTR_I2C_TFR_CMD	0x00	/* Transfer Command register */
> +#define     ALTR_I2C_TFR_CMD_STA	BIT(9)	/* send START before byte */
> +#define     ALTR_I2C_TFR_CMD_STO	BIT(8)	/* send STOP after byte */
> +#define     ALTR_I2C_TFR_CMD_RW_D	BIT(0)	/* Direction of transfer */
> +#define ALTR_I2C_RX_DATA	0x04	/* RX data FIFO register */
> +#define ALTR_I2C_CTRL		0x08	/* Control register */
> +#define     ALTR_I2C_CTRL_RXT_SHFT	4	/* RX FIFO Threshold */
> +#define     ALTR_I2C_CTRL_TCT_SHFT	2	/* TFER CMD FIFO Threshold */
> +#define     ALTR_I2C_CTRL_BSPEED	BIT(1)	/* Bus Speed (1=Fast) */
> +#define     ALTR_I2C_CTRL_EN	BIT(0)	/* Enable Core (1=Enable) */
> +#define ALTR_I2C_ISER		0x0C	/* Interrupt Status Enable register */
> +#define     ALTR_I2C_ISER_RXOF_EN	BIT(4)	/* Enable RX OVERFLOW IRQ */
> +#define     ALTR_I2C_ISER_ARB_EN	BIT(3)	/* Enable ARB LOST IRQ */
> +#define     ALTR_I2C_ISER_NACK_EN	BIT(2)	/* Enable NACK DET IRQ */
> +#define     ALTR_I2C_ISER_RXRDY_EN	BIT(1)	/* Enable RX Ready IRQ */
> +#define     ALTR_I2C_ISER_TXRDY_EN	BIT(0)	/* Enable TX Ready IRQ */
> +#define ALTR_I2C_ISR		0x10	/* Interrupt Status register */
> +#define     ALTR_I2C_ISR_RXOF		BIT(4)	/* RX OVERFLOW IRQ */
> +#define     ALTR_I2C_ISR_ARB		BIT(3)	/* ARB LOST IRQ */
> +#define     ALTR_I2C_ISR_NACK		BIT(2)	/* NACK DET IRQ */
> +#define     ALTR_I2C_ISR_RXRDY		BIT(1)	/* RX Ready IRQ */
> +#define     ALTR_I2C_ISR_TXRDY		BIT(0)	/* TX Ready IRQ */
> +#define ALTR_I2C_STATUS		0x14	/* Status register */
> +#define     ALTR_I2C_STAT_CORE		BIT(0)	/* Core Status (0=idle) */
> +#define ALTR_I2C_TC_FIFO_LVL	0x18	/* Transfer FIFO LVL register */
> +#define ALTR_I2C_RX_FIFO_LVL	0x1C	/* Receive FIFO LVL register */
> +#define ALTR_I2C_SCL_LOW	0x20	/* SCL low count register */
> +#define ALTR_I2C_SCL_HIGH	0x24	/* SCL high count register */
> +#define ALTR_I2C_SDA_HOLD	0x28	/* SDA hold count register */
> +
> +#define ALTR_I2C_ALL_IRQ	(ALTR_I2C_ISR_RXOF | ALTR_I2C_ISR_ARB | \
> +				 ALTR_I2C_ISR_NACK | ALTR_I2C_ISR_RXRDY | \
> +				 ALTR_I2C_ISR_TXRDY)
> +
> +#define ALTR_I2C_THRESHOLD	0	/* IRQ Threshold at 1 element */
> +#define ALTR_I2C_DFLT_FIFO_SZ	4
> +#define ALTR_I2C_TIMEOUT	100000	/* 100ms */
> +#define ALTR_I2C_XFER_TIMEOUT	(msecs_to_jiffies(250))
> +
> +/**
> + * altr_i2c_dev - I2C device context
> + * @base: pointer to register struct
> + * @msg: pointer to current message
> + * @msg_len: number of bytes transferred in msg
> + * @msg_err: error code for completed message
> + * @msg_complete: xfer completion object
> + * @dev: device reference
> + * @adapter: core i2c abstraction
> + * @i2c_clk: clock reference for i2c input clock
> + * @bus_clk_rate: current i2c bus clock rate
> + * @buf: ptr to msg buffer for easier use.
> + * @fifo_size: size of the FIFO passed in.
> + */
> +struct altr_i2c_dev {
> +	void __iomem *base;
> +	struct i2c_msg *msg;
> +	size_t msg_len;
> +	int msg_err;
> +	struct completion msg_complete;
> +	struct device *dev;
> +	struct i2c_adapter adapter;
> +	struct clk *i2c_clk;
> +	u32 bus_clk_rate;
> +	u8 *buf;
> +	u32 fifo_size;
> +	u32 isr_mask;

The last one is not described in the kernel docs.

> +};
> +
> +static void i2c_int_enable(struct altr_i2c_dev *idev, u32 mask, bool enable)
> +{
> +	u32 int_en = readl(idev->base + ALTR_I2C_ISER);
> +
> +	if (enable)
> +		idev->isr_mask = int_en | mask;
> +	else
> +		idev->isr_mask = int_en & ~mask;
> +
> +	writel(idev->isr_mask, idev->base + ALTR_I2C_ISER);
> +}
> +
> +static void i2c_int_clear(struct altr_i2c_dev *idev, u32 mask)
> +{
> +	u32 int_en = readl(idev->base + ALTR_I2C_ISR);
> +
> +	writel(int_en | mask, idev->base + ALTR_I2C_ISR);
> +}

Those two functions would also suit an altr_ prefix.

> +
> +static void altr_i2c_core_disable(struct altr_i2c_dev *idev)
> +{
> +	u32 tmp = readl(idev->base + ALTR_I2C_CTRL);
> +
> +	writel(tmp & ~ALTR_I2C_CTRL_EN, idev->base + ALTR_I2C_CTRL);
> +}
> +
> +static void altr_i2c_core_enable(struct altr_i2c_dev *idev)
> +{
> +	u32 tmp = readl(idev->base + ALTR_I2C_CTRL);
> +
> +	writel(tmp | ALTR_I2C_CTRL_EN, idev->base + ALTR_I2C_CTRL);
> +}
> +
> +static void altr_i2c_reset(struct altr_i2c_dev *idev)
> +{
> +	altr_i2c_core_disable(idev);
> +	altr_i2c_core_enable(idev);
> +}
> +
> +static void altr_i2c_recover(struct altr_i2c_dev *idev)
> +{
> +	altr_i2c_reset(idev);
> +	/* Clock start bit + 8 bits + stop bit out */

Really 8? It should be 9 (ACK bit).

> +	writel(ALTR_I2C_TFR_CMD_STA | ALTR_I2C_TFR_CMD_STO,
> +	       idev->base + ALTR_I2C_TFR_CMD);
> +	altr_i2c_reset(idev);

Why the second reset?

> +
> +	i2c_recover_bus(&idev->adapter);

This will return an error since you don't have a struct
i2c_bus_recovery_info defined. This whole recovery looks fishy, maybe it
should be dropped now and added incrementally?

> +}
> +
> +static inline void altr_i2c_stop(struct altr_i2c_dev *idev)
> +{
> +	writel(ALTR_I2C_TFR_CMD_STO, idev->base + ALTR_I2C_TFR_CMD);
> +}
> +
> +static void altr_i2c_init(struct altr_i2c_dev *idev)
> +{
> +	u32 divisor = clk_get_rate(idev->i2c_clk) / idev->bus_clk_rate;
> +	u32 clk_mhz = clk_get_rate(idev->i2c_clk) / 1000000;
> +	u32 tmp = (ALTR_I2C_THRESHOLD << ALTR_I2C_CTRL_RXT_SHFT) |
> +		  (ALTR_I2C_THRESHOLD << ALTR_I2C_CTRL_TCT_SHFT);
> +	u32 t_high, t_low;
> +
> +	if (idev->bus_clk_rate <= 100000) {
> +		tmp &= ~ALTR_I2C_CTRL_BSPEED;
> +		/* Standard mode SCL 50/50 */
> +		t_high = divisor * 1 / 2;
> +		t_low = divisor * 1 / 2;
> +	} else {
> +		tmp |= ALTR_I2C_CTRL_BSPEED;
> +		/* Fast mode SCL 33/66 */
> +		t_high = divisor * 1 / 3;
> +		t_low = divisor * 2 / 3;
> +	}
> +	writel(tmp, idev->base + ALTR_I2C_CTRL);
> +
> +	dev_dbg(idev->dev, "rate=%uHz per_clk=%uMHz -> ratio=1:%u\n",
> +		idev->bus_clk_rate, clk_mhz, divisor);
> +
> +	/* Reset controller */
> +	altr_i2c_reset(idev);
> +
> +	/* SCL High Time */
> +	writel(t_high, idev->base + ALTR_I2C_SCL_HIGH);
> +	/* SCL Low Time */
> +	writel(t_low, idev->base + ALTR_I2C_SCL_LOW);
> +	/* SDA Hold Time, 300ns */
> +	writel(div_u64(300 * clk_mhz, 1000), idev->base + ALTR_I2C_SDA_HOLD);
> +
> +	/* Mask all master interrupt bits */
> +	i2c_int_enable(idev, ALTR_I2C_ALL_IRQ, false);
> +}
> +
> +static int i2c_m_rd(const struct i2c_msg *msg)
> +{
> +	return (msg->flags & I2C_M_RD) != 0;
> +}

I'll leave it to you, but I'd think an extra function doesn't really
improve readability here.

> +
> +/**
> + * altr_i2c_transfer - On the last byte to be transmitted, send
> + * a Stop bit on the last byte.
> + */
> +static void altr_i2c_transfer(struct altr_i2c_dev *idev, u32 data)
> +{
> +	/* On the last byte to be transmitted, send STOP */
> +	if (idev->msg_len == 1)
> +		data |= ALTR_I2C_TFR_CMD_STO;
> +	if (idev->msg_len > 0)
> +		writel(data, idev->base + ALTR_I2C_TFR_CMD);
> +}
> +
> +/**
> + * altr_i2c_empty_rx_fifo - Fetch data from RX FIFO until end of
> + * transfer. Send a Stop bit on the last byte.
> + */
> +static void altr_i2c_empty_rx_fifo(struct altr_i2c_dev *idev)
> +{
> +	size_t rx_fifo_avail = readl(idev->base + ALTR_I2C_RX_FIFO_LVL);
> +	int bytes_to_transfer = min(rx_fifo_avail, idev->msg_len);
> +
> +	while (bytes_to_transfer-- > 0) {
> +		*idev->buf++ = readl(idev->base + ALTR_I2C_RX_DATA);
> +		idev->msg_len--;
> +		altr_i2c_transfer(idev, 0);
> +	}
> +}
> +
> +/**
> + * altr_i2c_fill_tx_fifo - Fill TX FIFO from current message buffer.
> + * @return: Number of bytes left to transfer.
> + */
> +static int altr_i2c_fill_tx_fifo(struct altr_i2c_dev *idev)
> +{
> +	size_t tx_fifo_avail = idev->fifo_size - readl(idev->base +
> +						       ALTR_I2C_TC_FIFO_LVL);
> +	int bytes_to_transfer = min(tx_fifo_avail, idev->msg_len);
> +	int ret = idev->msg_len - bytes_to_transfer;
> +
> +	while (bytes_to_transfer-- > 0) {
> +		altr_i2c_transfer(idev, *idev->buf++);
> +		idev->msg_len--;
> +	}
> +
> +	return ret;
> +}
> +
> +static irqreturn_t altr_i2c_isr(int irq, void *_dev)
> +{
> +	int ret, read;
> +	struct altr_i2c_dev *idev = _dev;
> +	/* Read IRQ status but only interested in Enabled IRQs. */
> +	u32 status = readl(idev->base + ALTR_I2C_ISR) & idev->isr_mask;
> +
> +	if (!idev->msg) {
> +		dev_warn(idev->dev, "unexpected interrupt\n");
> +		goto out;

Won't you get an interrupt storm if you don't use any i2c_int_clear()?

> +	}
> +	read = i2c_m_rd(idev->msg);
> +
> +	/* handle Lost Arbitration */
> +	if (unlikely(status & ALTR_I2C_ISR_ARB)) {
> +		dev_err(idev->dev, "%s: arbitration lost\n", __func__);

Drop the message, it is not an error, but a to be expected bus condition
in multi-master setups.

> +		i2c_int_clear(idev, ALTR_I2C_ISR_ARB);
> +		idev->msg_err = -EAGAIN;
> +		goto complete;
> +	}
> +
> +	if (unlikely(status & ALTR_I2C_ISR_NACK)) {
> +		dev_dbg(idev->dev, "%s: could not get ACK\n", __func__);
> +		idev->msg_err = -ENXIO;
> +		i2c_int_clear(idev, ALTR_I2C_ISR_NACK);
> +		altr_i2c_stop(idev);
> +		goto complete;
> +	}
> +
> +	/* handle RX FIFO Overflow */
> +	if (read && unlikely(status & ALTR_I2C_ISR_RXOF)) {
> +		altr_i2c_empty_rx_fifo(idev);
> +		i2c_int_clear(idev, ALTR_I2C_ISR_RXRDY);
> +		altr_i2c_stop(idev);
> +		dev_err(idev->dev, "%s: RX FIFO Overflow\n", __func__);
> +		goto complete;
> +	}
> +
> +	/* RX FIFO needs service? */
> +	if (read && (status & ALTR_I2C_ISR_RXRDY)) {
> +		altr_i2c_empty_rx_fifo(idev);
> +		i2c_int_clear(idev, ALTR_I2C_ISR_RXRDY);
> +		if (!idev->msg_len)
> +			goto complete;
> +
> +		goto out;
> +	}
> +
> +	/* TX FIFO needs service? */
> +	if (!read && (status & ALTR_I2C_ISR_TXRDY)) {
> +		i2c_int_clear(idev, ALTR_I2C_ISR_TXRDY);
> +		if (!altr_i2c_fill_tx_fifo(idev))
> +			goto complete;
> +
> +		goto out;

A bit too much goto in here for my taste. What about using a boolean
'complete' variable which gets set or cleared and have an 'if
(complete)' at the end of this routine?

> +	}
> +
> +complete:
> +	/* Wait for the Core to finish */
> +	ret = readl_poll_timeout_atomic(idev->base + ALTR_I2C_STATUS, status,
> +					((status & ALTR_I2C_STAT_CORE) == 0),
> +					1, ALTR_I2C_TIMEOUT);

Why do you need this polling in an interrupt?


> +	if (ret)
> +		dev_err(idev->dev, "%s: message timeout\n", __func__);
> +	i2c_int_enable(idev, ALTR_I2C_ALL_IRQ, false);
> +	i2c_int_clear(idev, ALTR_I2C_ALL_IRQ);
> +	complete(&idev->msg_complete);
> +	dev_dbg(idev->dev, "%s: Message Complete\n", __func__);
> +
> +out:
> +	return IRQ_HANDLED;
> +}
> +
> +static int altr_i2c_xfer_msg(struct altr_i2c_dev *idev, struct i2c_msg *msg)
> +{
> +	u32 imask = ALTR_I2C_ISR_RXOF | ALTR_I2C_ISR_ARB | ALTR_I2C_ISR_NACK;
> +	unsigned long time_left;
> +	u32 value;
> +	u8 addr = i2c_8bit_addr_from_msg(msg);
> +
> +	idev->msg = msg;
> +	idev->msg_len = msg->len;
> +	idev->buf = msg->buf;
> +	idev->msg_err = 0;
> +	reinit_completion(&idev->msg_complete);
> +	altr_i2c_core_enable(idev);
> +
> +	/* Make sure RX FIFO is empty */
> +	do {
> +		readl(idev->base + ALTR_I2C_RX_DATA);
> +	} while (readl(idev->base + ALTR_I2C_RX_FIFO_LVL));
> +
> +	writel(ALTR_I2C_TFR_CMD_STA | addr, idev->base + ALTR_I2C_TFR_CMD);
> +
> +	if (i2c_m_rd(msg)) {
> +		imask |= ALTR_I2C_ISER_RXOF_EN | ALTR_I2C_ISER_RXRDY_EN;
> +		i2c_int_enable(idev, imask, true);
> +		/* write the first byte to start the RX */
> +		altr_i2c_transfer(idev, 0);
> +	} else {
> +		imask |= ALTR_I2C_ISR_TXRDY;
> +		i2c_int_enable(idev, imask, true);
> +		altr_i2c_fill_tx_fifo(idev);
> +	}
> +
> +	time_left = wait_for_completion_timeout(&idev->msg_complete,
> +						ALTR_I2C_XFER_TIMEOUT);
> +	i2c_int_enable(idev, imask, false);
> +
> +	value = readl(idev->base + ALTR_I2C_STATUS) & ALTR_I2C_STAT_CORE;
> +	if (value)
> +		dev_err(idev->dev, "%s: Core Status not IDLE...\n", __func__);

__func__ with dev_* is 99,9% superfluous.

> +
> +	if (time_left == 0) {
> +		idev->msg_err = -ETIMEDOUT;
> +		dev_err(idev->dev, "%s: Transaction timed out.\n", __func__);

No error message here. This can happen when an EEPROM is currently
erasing.

> +		altr_i2c_recover(idev);

And no need to reset the bus! Only if SDA is stuck low.

> +	}
> +
> +	if (unlikely(idev->msg_err) && idev->msg_err != -ENXIO)
> +		altr_i2c_init(idev);

Why do you need to reinit on NACK?

> +
> +	altr_i2c_core_disable(idev);
> +
> +	return idev->msg_err;
> +}
> +
> +static int
> +altr_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
> +{
> +	struct altr_i2c_dev *idev = i2c_get_adapdata(adap);
> +	int i, ret;
> +
> +	for (i = 0; i < num; i++) {
> +		ret = altr_i2c_xfer_msg(idev, msgs++);
> +		if (ret)
> +			return ret;
> +	}
> +	return num;
> +}
> +
> +static u32 altr_i2c_func(struct i2c_adapter *adap)
> +{
> +	return I2C_FUNC_I2C;
> +}

No emulated SMBUS?

> +
> +static const struct i2c_algorithm altr_i2c_algo = {
> +	.master_xfer = altr_i2c_xfer,
> +	.functionality = altr_i2c_func,
> +};
> +
> +static int altr_i2c_probe(struct platform_device *pdev)
> +{
> +	struct altr_i2c_dev *idev = NULL;
> +	struct resource *res;
> +	int irq, ret;
> +	u32 val;
> +
> +	idev = devm_kzalloc(&pdev->dev, sizeof(*idev), GFP_KERNEL);
> +	if (!idev)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	idev->base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(idev->base))
> +		return PTR_ERR(idev->base);
> +
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0) {
> +		dev_err(&pdev->dev, "missing interrupt resource\n");
> +		return irq;
> +	}
> +
> +	idev->i2c_clk = devm_clk_get(&pdev->dev, NULL);
> +	if (IS_ERR(idev->i2c_clk)) {
> +		dev_err(&pdev->dev, "missing clock\n");
> +		return PTR_ERR(idev->i2c_clk);
> +	}
> +
> +	idev->dev = &pdev->dev;
> +	init_completion(&idev->msg_complete);
> +
> +	val = device_property_read_u32(idev->dev, "fifo-size",
> +				       &idev->fifo_size);
> +	if (val) {
> +		dev_err(&pdev->dev, "FIFO size set to default of %d\n",
> +			ALTR_I2C_DFLT_FIFO_SZ);
> +		idev->fifo_size = ALTR_I2C_DFLT_FIFO_SZ;
> +	}
> +
> +	val = device_property_read_u32(idev->dev, "clock-frequency",
> +				       &idev->bus_clk_rate);
> +	if (val) {
> +		dev_err(&pdev->dev, "Default to 100kHz\n");
> +		idev->bus_clk_rate = 100000;	/* default clock rate */
> +	}
> +
> +	if (idev->bus_clk_rate > 400000) {
> +		dev_err(&pdev->dev, "invalid clock-frequency %d\n",
> +			idev->bus_clk_rate);
> +		return -EINVAL;
> +	}
> +
> +	ret = devm_request_irq(&pdev->dev, irq, altr_i2c_isr, 0,
> +			       pdev->name, idev);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to claim IRQ %d\n", irq);
> +		return ret;
> +	}
> +
> +	ret = clk_prepare_enable(idev->i2c_clk);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to enable clock\n");
> +		return ret;
> +	}
> +
> +	altr_i2c_init(idev);
> +
> +	i2c_set_adapdata(&idev->adapter, idev);
> +	strlcpy(idev->adapter.name, pdev->name, sizeof(idev->adapter.name));
> +	idev->adapter.owner = THIS_MODULE;
> +	idev->adapter.algo = &altr_i2c_algo;
> +	idev->adapter.dev.parent = &pdev->dev;
> +	idev->adapter.dev.of_node = pdev->dev.of_node;
> +
> +	platform_set_drvdata(pdev, idev);
> +
> +	ret = i2c_add_adapter(&idev->adapter);
> +	if (ret) {
> +		clk_disable_unprepare(idev->i2c_clk);
> +		return ret;
> +	}
> +	dev_info(&pdev->dev, "Altera SoftIP I2C Probe Complete\n");
> +
> +	return 0;
> +}
> +
> +static int altr_i2c_remove(struct platform_device *pdev)
> +{
> +	struct altr_i2c_dev *idev = platform_get_drvdata(pdev);
> +
> +	clk_disable_unprepare(idev->i2c_clk);
> +	i2c_del_adapter(&idev->adapter);
> +
> +	return 0;
> +}
> +
> +/* Match table for of_platform binding */
> +static const struct of_device_id altr_i2c_of_match[] = {
> +	{ .compatible = "altr,softip-i2c-v1.0" },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, altr_i2c_of_match);
> +
> +static struct platform_driver altr_i2c_driver = {
> +	.probe = altr_i2c_probe,
> +	.remove = altr_i2c_remove,
> +	.driver = {
> +		.name = "altera-i2c",
> +		.of_match_table = altr_i2c_of_match,
> +	},
> +};
> +
> +module_platform_driver(altr_i2c_driver);
> +
> +MODULE_DESCRIPTION("Altera Soft IP I2C bus driver");
> +MODULE_AUTHOR("Thor Thayer <thor.thayer@linux.intel.com>");
> +MODULE_LICENSE("GPL v2");
> -- 
> 2.7.4
>
Thor Thayer July 31, 2017, 7:40 p.m. | #3
Hi Wolfram,

Thank you for reviewing.

On 07/31/2017 08:31 AM, Wolfram Sang wrote:
> Hi Thor,
> 
> thanks for the patches! A few comments and questions from me.
> 
> On Mon, Jul 17, 2017 at 11:35:14AM -0500, thor.thayer@linux.intel.com wrote:
>> From: Thor Thayer <thor.thayer@linux.intel.com>
>>
>> Add driver support for the Altera I2C Controller. The I2C
>> controller is soft IP for use in FPGAs.
>>
>> Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>
>> ---
>> v2  Remove altr, from fifo-size to agree with bindings.
>>      Change compatible string to "altr,softip-i2c"
>> v3  Add version to compatible string "altr,softip-i2c-v1.0"
>> v4  Add default 100kHz message. Cleanup IRQ error message.
>> v5  Cleanup header usage - remove init.h.
>>      Fix 1 byte RX bug and add convenience function for transfer shared by RX and TX.
>>      Use readl_poll_timeout_atomic() function.
>>      Cache the I2C Interrupt Status Enable Register.
>>      Cleanup of irq_mask by combining into 1 function.
>>      Use i2c_8bit_addr_from_msg() for cleaner xfer_msg implementation.
>>      Restructure altr_i2c_xfer() without arrays and indexes.
>>      Remove redundant assignments.
>>      Remove function calls from inside if() statements.
>>      Convert of_property_read_u32() to device_property_read_u32().
>>      Call i2c_m_read() once in irq.
>> ---
>>   drivers/i2c/busses/Kconfig      |  10 +
>>   drivers/i2c/busses/Makefile     |   1 +
>>   drivers/i2c/busses/i2c-altera.c | 510 ++++++++++++++++++++++++++++++++++++++++
>>   3 files changed, 521 insertions(+)

<snip>

>> new file mode 100644
>> index 0000000..e818901
>> --- /dev/null
>> +++ b/drivers/i2c/busses/i2c-altera.c
>> @@ -0,0 +1,510 @@

<snip>

>> +
>> +#define ALTR_I2C_THRESHOLD	0	/* IRQ Threshold at 1 element */
>> +#define ALTR_I2C_DFLT_FIFO_SZ	4
>> +#define ALTR_I2C_TIMEOUT	100000	/* 100ms */
>> +#define ALTR_I2C_XFER_TIMEOUT	(msecs_to_jiffies(250))
>> +
>> +/**
>> + * altr_i2c_dev - I2C device context
>> + * @base: pointer to register struct
>> + * @msg: pointer to current message
>> + * @msg_len: number of bytes transferred in msg
>> + * @msg_err: error code for completed message
>> + * @msg_complete: xfer completion object
>> + * @dev: device reference
>> + * @adapter: core i2c abstraction
>> + * @i2c_clk: clock reference for i2c input clock
>> + * @bus_clk_rate: current i2c bus clock rate
>> + * @buf: ptr to msg buffer for easier use.
>> + * @fifo_size: size of the FIFO passed in.
>> + */
>> +struct altr_i2c_dev {
>> +	void __iomem *base;
>> +	struct i2c_msg *msg;
>> +	size_t msg_len;
>> +	int msg_err;
>> +	struct completion msg_complete;
>> +	struct device *dev;
>> +	struct i2c_adapter adapter;
>> +	struct clk *i2c_clk;
>> +	u32 bus_clk_rate;
>> +	u8 *buf;
>> +	u32 fifo_size;
>> +	u32 isr_mask;
> 
> The last one is not described in the kernel docs.
> 

Whoops. Yes, I will add this.

>> +};
>> +
>> +static void i2c_int_enable(struct altr_i2c_dev *idev, u32 mask, bool enable)
>> +{
>> +	u32 int_en = readl(idev->base + ALTR_I2C_ISER);
>> +
>> +	if (enable)
>> +		idev->isr_mask = int_en | mask;
>> +	else
>> +		idev->isr_mask = int_en & ~mask;
>> +
>> +	writel(idev->isr_mask, idev->base + ALTR_I2C_ISER);
>> +}
>> +
>> +static void i2c_int_clear(struct altr_i2c_dev *idev, u32 mask)
>> +{
>> +	u32 int_en = readl(idev->base + ALTR_I2C_ISR);
>> +
>> +	writel(int_en | mask, idev->base + ALTR_I2C_ISR);
>> +}
> 
> Those two functions would also suit an altr_ prefix.
> 
Yes. I will fix this.

>> +
>> +static void altr_i2c_core_disable(struct altr_i2c_dev *idev)
>> +{
>> +	u32 tmp = readl(idev->base + ALTR_I2C_CTRL);
>> +
>> +	writel(tmp & ~ALTR_I2C_CTRL_EN, idev->base + ALTR_I2C_CTRL);
>> +}
>> +
>> +static void altr_i2c_core_enable(struct altr_i2c_dev *idev)
>> +{
>> +	u32 tmp = readl(idev->base + ALTR_I2C_CTRL);
>> +
>> +	writel(tmp | ALTR_I2C_CTRL_EN, idev->base + ALTR_I2C_CTRL);
>> +}
>> +
>> +static void altr_i2c_reset(struct altr_i2c_dev *idev)
>> +{
>> +	altr_i2c_core_disable(idev);
>> +	altr_i2c_core_enable(idev);
>> +}
>> +
>> +static void altr_i2c_recover(struct altr_i2c_dev *idev)
>> +{
>> +	altr_i2c_reset(idev);
>> +	/* Clock start bit + 8 bits + stop bit out */
> 
> Really 8? It should be 9 (ACK bit).
> 

Yes, I'll update the comment.

>> +	writel(ALTR_I2C_TFR_CMD_STA | ALTR_I2C_TFR_CMD_STO,
>> +	       idev->base + ALTR_I2C_TFR_CMD);
>> +	altr_i2c_reset(idev);
> 
> Why the second reset?
>

I wanted to start from a known clean condition. The first reset would 
reset the hardware. The 2nd would ensure the hardware is ready after 
clearing the bus. Maybe I'm being overly cautious but I don't have a way 
to check the status of the SDA line.

>> +
>> +	i2c_recover_bus(&idev->adapter);
> 
> This will return an error since you don't have a struct
> i2c_bus_recovery_info defined. This whole recovery looks fishy, maybe it
> should be dropped now and added incrementally?
>

Yes. I'll drop it for now. Thanks.

>> +}
>> +
>> +static inline void altr_i2c_stop(struct altr_i2c_dev *idev)
>> +{
>> +	writel(ALTR_I2C_TFR_CMD_STO, idev->base + ALTR_I2C_TFR_CMD);
>> +}
>> +
>> +static void altr_i2c_init(struct altr_i2c_dev *idev)
>> +{
>> +	u32 divisor = clk_get_rate(idev->i2c_clk) / idev->bus_clk_rate;
>> +	u32 clk_mhz = clk_get_rate(idev->i2c_clk) / 1000000;
>> +	u32 tmp = (ALTR_I2C_THRESHOLD << ALTR_I2C_CTRL_RXT_SHFT) |
>> +		  (ALTR_I2C_THRESHOLD << ALTR_I2C_CTRL_TCT_SHFT);
>> +	u32 t_high, t_low;
>> +
>> +	if (idev->bus_clk_rate <= 100000) {
>> +		tmp &= ~ALTR_I2C_CTRL_BSPEED;
>> +		/* Standard mode SCL 50/50 */
>> +		t_high = divisor * 1 / 2;
>> +		t_low = divisor * 1 / 2;
>> +	} else {
>> +		tmp |= ALTR_I2C_CTRL_BSPEED;
>> +		/* Fast mode SCL 33/66 */
>> +		t_high = divisor * 1 / 3;
>> +		t_low = divisor * 2 / 3;
>> +	}
>> +	writel(tmp, idev->base + ALTR_I2C_CTRL);
>> +
>> +	dev_dbg(idev->dev, "rate=%uHz per_clk=%uMHz -> ratio=1:%u\n",
>> +		idev->bus_clk_rate, clk_mhz, divisor);
>> +
>> +	/* Reset controller */
>> +	altr_i2c_reset(idev);
>> +
>> +	/* SCL High Time */
>> +	writel(t_high, idev->base + ALTR_I2C_SCL_HIGH);
>> +	/* SCL Low Time */
>> +	writel(t_low, idev->base + ALTR_I2C_SCL_LOW);
>> +	/* SDA Hold Time, 300ns */
>> +	writel(div_u64(300 * clk_mhz, 1000), idev->base + ALTR_I2C_SDA_HOLD);
>> +
>> +	/* Mask all master interrupt bits */
>> +	i2c_int_enable(idev, ALTR_I2C_ALL_IRQ, false);
>> +}
>> +
>> +static int i2c_m_rd(const struct i2c_msg *msg)
>> +{
>> +	return (msg->flags & I2C_M_RD) != 0;
>> +}
> 
> I'll leave it to you, but I'd think an extra function doesn't really
> improve readability here.
> 

OK. I'd seen others using it elsewhere and wanted to stay with 
convention but I'll just handle it directly. Thanks.

>> +
>> +/**
>> + * altr_i2c_transfer - On the last byte to be transmitted, send
>> + * a Stop bit on the last byte.
>> + */
>> +static void altr_i2c_transfer(struct altr_i2c_dev *idev, u32 data)
>> +{
>> +	/* On the last byte to be transmitted, send STOP */
>> +	if (idev->msg_len == 1)
>> +		data |= ALTR_I2C_TFR_CMD_STO;
>> +	if (idev->msg_len > 0)
>> +		writel(data, idev->base + ALTR_I2C_TFR_CMD);
>> +}
>> +
>> +/**
>> + * altr_i2c_empty_rx_fifo - Fetch data from RX FIFO until end of
>> + * transfer. Send a Stop bit on the last byte.
>> + */
>> +static void altr_i2c_empty_rx_fifo(struct altr_i2c_dev *idev)
>> +{
>> +	size_t rx_fifo_avail = readl(idev->base + ALTR_I2C_RX_FIFO_LVL);
>> +	int bytes_to_transfer = min(rx_fifo_avail, idev->msg_len);
>> +
>> +	while (bytes_to_transfer-- > 0) {
>> +		*idev->buf++ = readl(idev->base + ALTR_I2C_RX_DATA);
>> +		idev->msg_len--;
>> +		altr_i2c_transfer(idev, 0);
>> +	}
>> +}
>> +
>> +/**
>> + * altr_i2c_fill_tx_fifo - Fill TX FIFO from current message buffer.
>> + * @return: Number of bytes left to transfer.
>> + */
>> +static int altr_i2c_fill_tx_fifo(struct altr_i2c_dev *idev)
>> +{
>> +	size_t tx_fifo_avail = idev->fifo_size - readl(idev->base +
>> +						       ALTR_I2C_TC_FIFO_LVL);
>> +	int bytes_to_transfer = min(tx_fifo_avail, idev->msg_len);
>> +	int ret = idev->msg_len - bytes_to_transfer;
>> +
>> +	while (bytes_to_transfer-- > 0) {
>> +		altr_i2c_transfer(idev, *idev->buf++);
>> +		idev->msg_len--;
>> +	}
>> +
>> +	return ret;
>> +}
>> +
>> +static irqreturn_t altr_i2c_isr(int irq, void *_dev)
>> +{
>> +	int ret, read;
>> +	struct altr_i2c_dev *idev = _dev;
>> +	/* Read IRQ status but only interested in Enabled IRQs. */
>> +	u32 status = readl(idev->base + ALTR_I2C_ISR) & idev->isr_mask;
>> +
>> +	if (!idev->msg) {
>> +		dev_warn(idev->dev, "unexpected interrupt\n");
>> +		goto out;
> 
> Won't you get an interrupt storm if you don't use any i2c_int_clear()?
> 

Yes. I missed that. Thanks.

>> +	}
>> +	read = i2c_m_rd(idev->msg);
>> +
>> +	/* handle Lost Arbitration */
>> +	if (unlikely(status & ALTR_I2C_ISR_ARB)) {
>> +		dev_err(idev->dev, "%s: arbitration lost\n", __func__);
> 
> Drop the message, it is not an error, but a to be expected bus condition
> in multi-master setups.

OK. Thanks.

> 
>> +		i2c_int_clear(idev, ALTR_I2C_ISR_ARB);
>> +		idev->msg_err = -EAGAIN;
>> +		goto complete;
>> +	}
>> +
>> +	if (unlikely(status & ALTR_I2C_ISR_NACK)) {
>> +		dev_dbg(idev->dev, "%s: could not get ACK\n", __func__);
>> +		idev->msg_err = -ENXIO;
>> +		i2c_int_clear(idev, ALTR_I2C_ISR_NACK);
>> +		altr_i2c_stop(idev);
>> +		goto complete;
>> +	}
>> +
>> +	/* handle RX FIFO Overflow */
>> +	if (read && unlikely(status & ALTR_I2C_ISR_RXOF)) {
>> +		altr_i2c_empty_rx_fifo(idev);
>> +		i2c_int_clear(idev, ALTR_I2C_ISR_RXRDY);
>> +		altr_i2c_stop(idev);
>> +		dev_err(idev->dev, "%s: RX FIFO Overflow\n", __func__);
>> +		goto complete;
>> +	}
>> +
>> +	/* RX FIFO needs service? */
>> +	if (read && (status & ALTR_I2C_ISR_RXRDY)) {
>> +		altr_i2c_empty_rx_fifo(idev);
>> +		i2c_int_clear(idev, ALTR_I2C_ISR_RXRDY);
>> +		if (!idev->msg_len)
>> +			goto complete;
>> +
>> +		goto out;
>> +	}
>> +
>> +	/* TX FIFO needs service? */
>> +	if (!read && (status & ALTR_I2C_ISR_TXRDY)) {
>> +		i2c_int_clear(idev, ALTR_I2C_ISR_TXRDY);
>> +		if (!altr_i2c_fill_tx_fifo(idev))
>> +			goto complete;
>> +
>> +		goto out;
> 
> A bit too much goto in here for my taste. What about using a boolean
> 'complete' variable which gets set or cleared and have an 'if
> (complete)' at the end of this routine?
> 

I want to exit immediately on an error - without checking any further 
errors or RX or TX. Maybe a switch/case statement would be better.

Yes, the boolean would be cleaner. I will look at better ways to handle 
the sequence.  Andy's last comment indicated something similar. Thanks.

>> +	}
>> +
>> +complete:
>> +	/* Wait for the Core to finish */
>> +	ret = readl_poll_timeout_atomic(idev->base + ALTR_I2C_STATUS, status,
>> +					((status & ALTR_I2C_STAT_CORE) == 0),
>> +					1, ALTR_I2C_TIMEOUT);
> 
> Why do you need this polling in an interrupt?
> 

I wanted to wait for completion before marking it as complete. As you 
point out, this isn't appropriate in an interrupt handler. I will look 
at this again. Thanks for pointing this out.

> 
>> +	if (ret)
>> +		dev_err(idev->dev, "%s: message timeout\n", __func__);
>> +	i2c_int_enable(idev, ALTR_I2C_ALL_IRQ, false);
>> +	i2c_int_clear(idev, ALTR_I2C_ALL_IRQ);
>> +	complete(&idev->msg_complete);
>> +	dev_dbg(idev->dev, "%s: Message Complete\n", __func__);
>> +
>> +out:
>> +	return IRQ_HANDLED;
>> +}
>> +
>> +static int altr_i2c_xfer_msg(struct altr_i2c_dev *idev, struct i2c_msg *msg)
>> +{
>> +	u32 imask = ALTR_I2C_ISR_RXOF | ALTR_I2C_ISR_ARB | ALTR_I2C_ISR_NACK;
>> +	unsigned long time_left;
>> +	u32 value;
>> +	u8 addr = i2c_8bit_addr_from_msg(msg);
>> +
>> +	idev->msg = msg;
>> +	idev->msg_len = msg->len;
>> +	idev->buf = msg->buf;
>> +	idev->msg_err = 0;
>> +	reinit_completion(&idev->msg_complete);
>> +	altr_i2c_core_enable(idev);
>> +
>> +	/* Make sure RX FIFO is empty */
>> +	do {
>> +		readl(idev->base + ALTR_I2C_RX_DATA);
>> +	} while (readl(idev->base + ALTR_I2C_RX_FIFO_LVL));
>> +
>> +	writel(ALTR_I2C_TFR_CMD_STA | addr, idev->base + ALTR_I2C_TFR_CMD);
>> +
>> +	if (i2c_m_rd(msg)) {
>> +		imask |= ALTR_I2C_ISER_RXOF_EN | ALTR_I2C_ISER_RXRDY_EN;
>> +		i2c_int_enable(idev, imask, true);
>> +		/* write the first byte to start the RX */
>> +		altr_i2c_transfer(idev, 0);
>> +	} else {
>> +		imask |= ALTR_I2C_ISR_TXRDY;
>> +		i2c_int_enable(idev, imask, true);
>> +		altr_i2c_fill_tx_fifo(idev);
>> +	}
>> +
>> +	time_left = wait_for_completion_timeout(&idev->msg_complete,
>> +						ALTR_I2C_XFER_TIMEOUT);
>> +	i2c_int_enable(idev, imask, false);
>> +
>> +	value = readl(idev->base + ALTR_I2C_STATUS) & ALTR_I2C_STAT_CORE;
>> +	if (value)
>> +		dev_err(idev->dev, "%s: Core Status not IDLE...\n", __func__);
> 
> __func__ with dev_* is 99,9% superfluous.
> 

I will remove this and the other ones above. Andy indicated this as well.

>> +
>> +	if (time_left == 0) {
>> +		idev->msg_err = -ETIMEDOUT;
>> +		dev_err(idev->dev, "%s: Transaction timed out.\n", __func__);
> 
> No error message here. This can happen when an EEPROM is currently
> erasing.
> 

OK.

>> +		altr_i2c_recover(idev);
> 
> And no need to reset the bus! Only if SDA is stuck low.
> 

OK. Unfortunately, we can't check the state of the SDA line so I was 
being extra cautious. I will remove it.

>> +	}
>> +
>> +	if (unlikely(idev->msg_err) && idev->msg_err != -ENXIO)
>> +		altr_i2c_init(idev);
> 
> Why do you need to reinit on NACK?
> 

OK. Thanks.

>> +
>> +	altr_i2c_core_disable(idev);
>> +
>> +	return idev->msg_err;
>> +}
>> +
>> +static int
>> +altr_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
>> +{
>> +	struct altr_i2c_dev *idev = i2c_get_adapdata(adap);
>> +	int i, ret;
>> +
>> +	for (i = 0; i < num; i++) {
>> +		ret = altr_i2c_xfer_msg(idev, msgs++);
>> +		if (ret)
>> +			return ret;
>> +	}
>> +	return num;
>> +}
>> +
>> +static u32 altr_i2c_func(struct i2c_adapter *adap)
>> +{
>> +	return I2C_FUNC_I2C;
>> +}
> 
> No emulated SMBUS?
> 

I was focusing on I2C and wasn't sure about SMBus (particularly the 
minimum clock speed). SMBus could be added later but would require some 
IP changes.

<snip>
Wolfram Sang July 31, 2017, 8:16 p.m. | #4
> >>+	writel(ALTR_I2C_TFR_CMD_STA | ALTR_I2C_TFR_CMD_STO,
> >>+	       idev->base + ALTR_I2C_TFR_CMD);
> >>+	altr_i2c_reset(idev);
> >
> >Why the second reset?
> >
> 
> I wanted to start from a known clean condition. The first reset would reset
> the hardware. The 2nd would ensure the hardware is ready after clearing the
> bus. Maybe I'm being overly cautious but I don't have a way to check the
> status of the SDA line.

Well, it looks like the function will go for now anyhow...

> >>+		altr_i2c_recover(idev);
> >
> >And no need to reset the bus! Only if SDA is stuck low.
> >
> 
> OK. Unfortunately, we can't check the state of the SDA line so I was being
> extra cautious. I will remove it.

Thanks. Bus recovery really needs a testcase to be checked against.

> >>+static u32 altr_i2c_func(struct i2c_adapter *adap)
> >>+{
> >>+	return I2C_FUNC_I2C;
> >>+}
> >
> >No emulated SMBUS?
> >
> 
> I was focusing on I2C and wasn't sure about SMBus (particularly the minimum
> clock speed). SMBus could be added later but would require some IP changes.

I meant you can add I2C_FUNC_SMBUS_EMUL which makes the I2C core emulate
SMBus-style transactions via I2C messages for you. A lot of drivers
won't work if you don't have this.

Patch

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 1006b23..668147bf 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -328,6 +328,16 @@  config I2C_POWERMAC
 
 comment "I2C system bus drivers (mostly embedded / system-on-chip)"
 
+config I2C_ALTERA
+	tristate "Altera Soft IP I2C"
+	depends on (ARCH_SOCFPGA || NIOS2) && OF
+	help
+	  If you say yes to this option, support will be included for the
+	  Altera Soft IP I2C interfaces on SoCFPGA and Nios2 architectures.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called i2c-altera.
+
 config I2C_ASPEED
 	tristate "Aspeed I2C Controller"
 	depends on ARCH_ASPEED || COMPILE_TEST
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 1b2fc81..1395dcb 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -29,6 +29,7 @@  obj-$(CONFIG_I2C_HYDRA)		+= i2c-hydra.o
 obj-$(CONFIG_I2C_POWERMAC)	+= i2c-powermac.o
 
 # Embedded system I2C/SMBus host controller drivers
+obj-$(CONFIG_I2C_ALTERA)	+= i2c-altera.o
 obj-$(CONFIG_I2C_ASPEED)	+= i2c-aspeed.o
 obj-$(CONFIG_I2C_AT91)		+= i2c-at91.o
 obj-$(CONFIG_I2C_AU1550)	+= i2c-au1550.o
diff --git a/drivers/i2c/busses/i2c-altera.c b/drivers/i2c/busses/i2c-altera.c
new file mode 100644
index 0000000..e818901
--- /dev/null
+++ b/drivers/i2c/busses/i2c-altera.c
@@ -0,0 +1,510 @@ 
+/*
+ *  Copyright Intel Corporation (C) 2017.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Based on the i2c-axxia.c driver.
+ */
+#include <linux/clk.h>
+#include <linux/clkdev.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/iopoll.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+
+#define ALTR_I2C_TFR_CMD	0x00	/* Transfer Command register */
+#define     ALTR_I2C_TFR_CMD_STA	BIT(9)	/* send START before byte */
+#define     ALTR_I2C_TFR_CMD_STO	BIT(8)	/* send STOP after byte */
+#define     ALTR_I2C_TFR_CMD_RW_D	BIT(0)	/* Direction of transfer */
+#define ALTR_I2C_RX_DATA	0x04	/* RX data FIFO register */
+#define ALTR_I2C_CTRL		0x08	/* Control register */
+#define     ALTR_I2C_CTRL_RXT_SHFT	4	/* RX FIFO Threshold */
+#define     ALTR_I2C_CTRL_TCT_SHFT	2	/* TFER CMD FIFO Threshold */
+#define     ALTR_I2C_CTRL_BSPEED	BIT(1)	/* Bus Speed (1=Fast) */
+#define     ALTR_I2C_CTRL_EN	BIT(0)	/* Enable Core (1=Enable) */
+#define ALTR_I2C_ISER		0x0C	/* Interrupt Status Enable register */
+#define     ALTR_I2C_ISER_RXOF_EN	BIT(4)	/* Enable RX OVERFLOW IRQ */
+#define     ALTR_I2C_ISER_ARB_EN	BIT(3)	/* Enable ARB LOST IRQ */
+#define     ALTR_I2C_ISER_NACK_EN	BIT(2)	/* Enable NACK DET IRQ */
+#define     ALTR_I2C_ISER_RXRDY_EN	BIT(1)	/* Enable RX Ready IRQ */
+#define     ALTR_I2C_ISER_TXRDY_EN	BIT(0)	/* Enable TX Ready IRQ */
+#define ALTR_I2C_ISR		0x10	/* Interrupt Status register */
+#define     ALTR_I2C_ISR_RXOF		BIT(4)	/* RX OVERFLOW IRQ */
+#define     ALTR_I2C_ISR_ARB		BIT(3)	/* ARB LOST IRQ */
+#define     ALTR_I2C_ISR_NACK		BIT(2)	/* NACK DET IRQ */
+#define     ALTR_I2C_ISR_RXRDY		BIT(1)	/* RX Ready IRQ */
+#define     ALTR_I2C_ISR_TXRDY		BIT(0)	/* TX Ready IRQ */
+#define ALTR_I2C_STATUS		0x14	/* Status register */
+#define     ALTR_I2C_STAT_CORE		BIT(0)	/* Core Status (0=idle) */
+#define ALTR_I2C_TC_FIFO_LVL	0x18	/* Transfer FIFO LVL register */
+#define ALTR_I2C_RX_FIFO_LVL	0x1C	/* Receive FIFO LVL register */
+#define ALTR_I2C_SCL_LOW	0x20	/* SCL low count register */
+#define ALTR_I2C_SCL_HIGH	0x24	/* SCL high count register */
+#define ALTR_I2C_SDA_HOLD	0x28	/* SDA hold count register */
+
+#define ALTR_I2C_ALL_IRQ	(ALTR_I2C_ISR_RXOF | ALTR_I2C_ISR_ARB | \
+				 ALTR_I2C_ISR_NACK | ALTR_I2C_ISR_RXRDY | \
+				 ALTR_I2C_ISR_TXRDY)
+
+#define ALTR_I2C_THRESHOLD	0	/* IRQ Threshold at 1 element */
+#define ALTR_I2C_DFLT_FIFO_SZ	4
+#define ALTR_I2C_TIMEOUT	100000	/* 100ms */
+#define ALTR_I2C_XFER_TIMEOUT	(msecs_to_jiffies(250))
+
+/**
+ * altr_i2c_dev - I2C device context
+ * @base: pointer to register struct
+ * @msg: pointer to current message
+ * @msg_len: number of bytes transferred in msg
+ * @msg_err: error code for completed message
+ * @msg_complete: xfer completion object
+ * @dev: device reference
+ * @adapter: core i2c abstraction
+ * @i2c_clk: clock reference for i2c input clock
+ * @bus_clk_rate: current i2c bus clock rate
+ * @buf: ptr to msg buffer for easier use.
+ * @fifo_size: size of the FIFO passed in.
+ */
+struct altr_i2c_dev {
+	void __iomem *base;
+	struct i2c_msg *msg;
+	size_t msg_len;
+	int msg_err;
+	struct completion msg_complete;
+	struct device *dev;
+	struct i2c_adapter adapter;
+	struct clk *i2c_clk;
+	u32 bus_clk_rate;
+	u8 *buf;
+	u32 fifo_size;
+	u32 isr_mask;
+};
+
+static void i2c_int_enable(struct altr_i2c_dev *idev, u32 mask, bool enable)
+{
+	u32 int_en = readl(idev->base + ALTR_I2C_ISER);
+
+	if (enable)
+		idev->isr_mask = int_en | mask;
+	else
+		idev->isr_mask = int_en & ~mask;
+
+	writel(idev->isr_mask, idev->base + ALTR_I2C_ISER);
+}
+
+static void i2c_int_clear(struct altr_i2c_dev *idev, u32 mask)
+{
+	u32 int_en = readl(idev->base + ALTR_I2C_ISR);
+
+	writel(int_en | mask, idev->base + ALTR_I2C_ISR);
+}
+
+static void altr_i2c_core_disable(struct altr_i2c_dev *idev)
+{
+	u32 tmp = readl(idev->base + ALTR_I2C_CTRL);
+
+	writel(tmp & ~ALTR_I2C_CTRL_EN, idev->base + ALTR_I2C_CTRL);
+}
+
+static void altr_i2c_core_enable(struct altr_i2c_dev *idev)
+{
+	u32 tmp = readl(idev->base + ALTR_I2C_CTRL);
+
+	writel(tmp | ALTR_I2C_CTRL_EN, idev->base + ALTR_I2C_CTRL);
+}
+
+static void altr_i2c_reset(struct altr_i2c_dev *idev)
+{
+	altr_i2c_core_disable(idev);
+	altr_i2c_core_enable(idev);
+}
+
+static void altr_i2c_recover(struct altr_i2c_dev *idev)
+{
+	altr_i2c_reset(idev);
+	/* Clock start bit + 8 bits + stop bit out */
+	writel(ALTR_I2C_TFR_CMD_STA | ALTR_I2C_TFR_CMD_STO,
+	       idev->base + ALTR_I2C_TFR_CMD);
+	altr_i2c_reset(idev);
+
+	i2c_recover_bus(&idev->adapter);
+}
+
+static inline void altr_i2c_stop(struct altr_i2c_dev *idev)
+{
+	writel(ALTR_I2C_TFR_CMD_STO, idev->base + ALTR_I2C_TFR_CMD);
+}
+
+static void altr_i2c_init(struct altr_i2c_dev *idev)
+{
+	u32 divisor = clk_get_rate(idev->i2c_clk) / idev->bus_clk_rate;
+	u32 clk_mhz = clk_get_rate(idev->i2c_clk) / 1000000;
+	u32 tmp = (ALTR_I2C_THRESHOLD << ALTR_I2C_CTRL_RXT_SHFT) |
+		  (ALTR_I2C_THRESHOLD << ALTR_I2C_CTRL_TCT_SHFT);
+	u32 t_high, t_low;
+
+	if (idev->bus_clk_rate <= 100000) {
+		tmp &= ~ALTR_I2C_CTRL_BSPEED;
+		/* Standard mode SCL 50/50 */
+		t_high = divisor * 1 / 2;
+		t_low = divisor * 1 / 2;
+	} else {
+		tmp |= ALTR_I2C_CTRL_BSPEED;
+		/* Fast mode SCL 33/66 */
+		t_high = divisor * 1 / 3;
+		t_low = divisor * 2 / 3;
+	}
+	writel(tmp, idev->base + ALTR_I2C_CTRL);
+
+	dev_dbg(idev->dev, "rate=%uHz per_clk=%uMHz -> ratio=1:%u\n",
+		idev->bus_clk_rate, clk_mhz, divisor);
+
+	/* Reset controller */
+	altr_i2c_reset(idev);
+
+	/* SCL High Time */
+	writel(t_high, idev->base + ALTR_I2C_SCL_HIGH);
+	/* SCL Low Time */
+	writel(t_low, idev->base + ALTR_I2C_SCL_LOW);
+	/* SDA Hold Time, 300ns */
+	writel(div_u64(300 * clk_mhz, 1000), idev->base + ALTR_I2C_SDA_HOLD);
+
+	/* Mask all master interrupt bits */
+	i2c_int_enable(idev, ALTR_I2C_ALL_IRQ, false);
+}
+
+static int i2c_m_rd(const struct i2c_msg *msg)
+{
+	return (msg->flags & I2C_M_RD) != 0;
+}
+
+/**
+ * altr_i2c_transfer - On the last byte to be transmitted, send
+ * a Stop bit on the last byte.
+ */
+static void altr_i2c_transfer(struct altr_i2c_dev *idev, u32 data)
+{
+	/* On the last byte to be transmitted, send STOP */
+	if (idev->msg_len == 1)
+		data |= ALTR_I2C_TFR_CMD_STO;
+	if (idev->msg_len > 0)
+		writel(data, idev->base + ALTR_I2C_TFR_CMD);
+}
+
+/**
+ * altr_i2c_empty_rx_fifo - Fetch data from RX FIFO until end of
+ * transfer. Send a Stop bit on the last byte.
+ */
+static void altr_i2c_empty_rx_fifo(struct altr_i2c_dev *idev)
+{
+	size_t rx_fifo_avail = readl(idev->base + ALTR_I2C_RX_FIFO_LVL);
+	int bytes_to_transfer = min(rx_fifo_avail, idev->msg_len);
+
+	while (bytes_to_transfer-- > 0) {
+		*idev->buf++ = readl(idev->base + ALTR_I2C_RX_DATA);
+		idev->msg_len--;
+		altr_i2c_transfer(idev, 0);
+	}
+}
+
+/**
+ * altr_i2c_fill_tx_fifo - Fill TX FIFO from current message buffer.
+ * @return: Number of bytes left to transfer.
+ */
+static int altr_i2c_fill_tx_fifo(struct altr_i2c_dev *idev)
+{
+	size_t tx_fifo_avail = idev->fifo_size - readl(idev->base +
+						       ALTR_I2C_TC_FIFO_LVL);
+	int bytes_to_transfer = min(tx_fifo_avail, idev->msg_len);
+	int ret = idev->msg_len - bytes_to_transfer;
+
+	while (bytes_to_transfer-- > 0) {
+		altr_i2c_transfer(idev, *idev->buf++);
+		idev->msg_len--;
+	}
+
+	return ret;
+}
+
+static irqreturn_t altr_i2c_isr(int irq, void *_dev)
+{
+	int ret, read;
+	struct altr_i2c_dev *idev = _dev;
+	/* Read IRQ status but only interested in Enabled IRQs. */
+	u32 status = readl(idev->base + ALTR_I2C_ISR) & idev->isr_mask;
+
+	if (!idev->msg) {
+		dev_warn(idev->dev, "unexpected interrupt\n");
+		goto out;
+	}
+	read = i2c_m_rd(idev->msg);
+
+	/* handle Lost Arbitration */
+	if (unlikely(status & ALTR_I2C_ISR_ARB)) {
+		dev_err(idev->dev, "%s: arbitration lost\n", __func__);
+		i2c_int_clear(idev, ALTR_I2C_ISR_ARB);
+		idev->msg_err = -EAGAIN;
+		goto complete;
+	}
+
+	if (unlikely(status & ALTR_I2C_ISR_NACK)) {
+		dev_dbg(idev->dev, "%s: could not get ACK\n", __func__);
+		idev->msg_err = -ENXIO;
+		i2c_int_clear(idev, ALTR_I2C_ISR_NACK);
+		altr_i2c_stop(idev);
+		goto complete;
+	}
+
+	/* handle RX FIFO Overflow */
+	if (read && unlikely(status & ALTR_I2C_ISR_RXOF)) {
+		altr_i2c_empty_rx_fifo(idev);
+		i2c_int_clear(idev, ALTR_I2C_ISR_RXRDY);
+		altr_i2c_stop(idev);
+		dev_err(idev->dev, "%s: RX FIFO Overflow\n", __func__);
+		goto complete;
+	}
+
+	/* RX FIFO needs service? */
+	if (read && (status & ALTR_I2C_ISR_RXRDY)) {
+		altr_i2c_empty_rx_fifo(idev);
+		i2c_int_clear(idev, ALTR_I2C_ISR_RXRDY);
+		if (!idev->msg_len)
+			goto complete;
+
+		goto out;
+	}
+
+	/* TX FIFO needs service? */
+	if (!read && (status & ALTR_I2C_ISR_TXRDY)) {
+		i2c_int_clear(idev, ALTR_I2C_ISR_TXRDY);
+		if (!altr_i2c_fill_tx_fifo(idev))
+			goto complete;
+
+		goto out;
+	}
+
+complete:
+	/* Wait for the Core to finish */
+	ret = readl_poll_timeout_atomic(idev->base + ALTR_I2C_STATUS, status,
+					((status & ALTR_I2C_STAT_CORE) == 0),
+					1, ALTR_I2C_TIMEOUT);
+	if (ret)
+		dev_err(idev->dev, "%s: message timeout\n", __func__);
+	i2c_int_enable(idev, ALTR_I2C_ALL_IRQ, false);
+	i2c_int_clear(idev, ALTR_I2C_ALL_IRQ);
+	complete(&idev->msg_complete);
+	dev_dbg(idev->dev, "%s: Message Complete\n", __func__);
+
+out:
+	return IRQ_HANDLED;
+}
+
+static int altr_i2c_xfer_msg(struct altr_i2c_dev *idev, struct i2c_msg *msg)
+{
+	u32 imask = ALTR_I2C_ISR_RXOF | ALTR_I2C_ISR_ARB | ALTR_I2C_ISR_NACK;
+	unsigned long time_left;
+	u32 value;
+	u8 addr = i2c_8bit_addr_from_msg(msg);
+
+	idev->msg = msg;
+	idev->msg_len = msg->len;
+	idev->buf = msg->buf;
+	idev->msg_err = 0;
+	reinit_completion(&idev->msg_complete);
+	altr_i2c_core_enable(idev);
+
+	/* Make sure RX FIFO is empty */
+	do {
+		readl(idev->base + ALTR_I2C_RX_DATA);
+	} while (readl(idev->base + ALTR_I2C_RX_FIFO_LVL));
+
+	writel(ALTR_I2C_TFR_CMD_STA | addr, idev->base + ALTR_I2C_TFR_CMD);
+
+	if (i2c_m_rd(msg)) {
+		imask |= ALTR_I2C_ISER_RXOF_EN | ALTR_I2C_ISER_RXRDY_EN;
+		i2c_int_enable(idev, imask, true);
+		/* write the first byte to start the RX */
+		altr_i2c_transfer(idev, 0);
+	} else {
+		imask |= ALTR_I2C_ISR_TXRDY;
+		i2c_int_enable(idev, imask, true);
+		altr_i2c_fill_tx_fifo(idev);
+	}
+
+	time_left = wait_for_completion_timeout(&idev->msg_complete,
+						ALTR_I2C_XFER_TIMEOUT);
+	i2c_int_enable(idev, imask, false);
+
+	value = readl(idev->base + ALTR_I2C_STATUS) & ALTR_I2C_STAT_CORE;
+	if (value)
+		dev_err(idev->dev, "%s: Core Status not IDLE...\n", __func__);
+
+	if (time_left == 0) {
+		idev->msg_err = -ETIMEDOUT;
+		dev_err(idev->dev, "%s: Transaction timed out.\n", __func__);
+		altr_i2c_recover(idev);
+	}
+
+	if (unlikely(idev->msg_err) && idev->msg_err != -ENXIO)
+		altr_i2c_init(idev);
+
+	altr_i2c_core_disable(idev);
+
+	return idev->msg_err;
+}
+
+static int
+altr_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
+{
+	struct altr_i2c_dev *idev = i2c_get_adapdata(adap);
+	int i, ret;
+
+	for (i = 0; i < num; i++) {
+		ret = altr_i2c_xfer_msg(idev, msgs++);
+		if (ret)
+			return ret;
+	}
+	return num;
+}
+
+static u32 altr_i2c_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C;
+}
+
+static const struct i2c_algorithm altr_i2c_algo = {
+	.master_xfer = altr_i2c_xfer,
+	.functionality = altr_i2c_func,
+};
+
+static int altr_i2c_probe(struct platform_device *pdev)
+{
+	struct altr_i2c_dev *idev = NULL;
+	struct resource *res;
+	int irq, ret;
+	u32 val;
+
+	idev = devm_kzalloc(&pdev->dev, sizeof(*idev), GFP_KERNEL);
+	if (!idev)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	idev->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(idev->base))
+		return PTR_ERR(idev->base);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		dev_err(&pdev->dev, "missing interrupt resource\n");
+		return irq;
+	}
+
+	idev->i2c_clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(idev->i2c_clk)) {
+		dev_err(&pdev->dev, "missing clock\n");
+		return PTR_ERR(idev->i2c_clk);
+	}
+
+	idev->dev = &pdev->dev;
+	init_completion(&idev->msg_complete);
+
+	val = device_property_read_u32(idev->dev, "fifo-size",
+				       &idev->fifo_size);
+	if (val) {
+		dev_err(&pdev->dev, "FIFO size set to default of %d\n",
+			ALTR_I2C_DFLT_FIFO_SZ);
+		idev->fifo_size = ALTR_I2C_DFLT_FIFO_SZ;
+	}
+
+	val = device_property_read_u32(idev->dev, "clock-frequency",
+				       &idev->bus_clk_rate);
+	if (val) {
+		dev_err(&pdev->dev, "Default to 100kHz\n");
+		idev->bus_clk_rate = 100000;	/* default clock rate */
+	}
+
+	if (idev->bus_clk_rate > 400000) {
+		dev_err(&pdev->dev, "invalid clock-frequency %d\n",
+			idev->bus_clk_rate);
+		return -EINVAL;
+	}
+
+	ret = devm_request_irq(&pdev->dev, irq, altr_i2c_isr, 0,
+			       pdev->name, idev);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to claim IRQ %d\n", irq);
+		return ret;
+	}
+
+	ret = clk_prepare_enable(idev->i2c_clk);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to enable clock\n");
+		return ret;
+	}
+
+	altr_i2c_init(idev);
+
+	i2c_set_adapdata(&idev->adapter, idev);
+	strlcpy(idev->adapter.name, pdev->name, sizeof(idev->adapter.name));
+	idev->adapter.owner = THIS_MODULE;
+	idev->adapter.algo = &altr_i2c_algo;
+	idev->adapter.dev.parent = &pdev->dev;
+	idev->adapter.dev.of_node = pdev->dev.of_node;
+
+	platform_set_drvdata(pdev, idev);
+
+	ret = i2c_add_adapter(&idev->adapter);
+	if (ret) {
+		clk_disable_unprepare(idev->i2c_clk);
+		return ret;
+	}
+	dev_info(&pdev->dev, "Altera SoftIP I2C Probe Complete\n");
+
+	return 0;
+}
+
+static int altr_i2c_remove(struct platform_device *pdev)
+{
+	struct altr_i2c_dev *idev = platform_get_drvdata(pdev);
+
+	clk_disable_unprepare(idev->i2c_clk);
+	i2c_del_adapter(&idev->adapter);
+
+	return 0;
+}
+
+/* Match table for of_platform binding */
+static const struct of_device_id altr_i2c_of_match[] = {
+	{ .compatible = "altr,softip-i2c-v1.0" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, altr_i2c_of_match);
+
+static struct platform_driver altr_i2c_driver = {
+	.probe = altr_i2c_probe,
+	.remove = altr_i2c_remove,
+	.driver = {
+		.name = "altera-i2c",
+		.of_match_table = altr_i2c_of_match,
+	},
+};
+
+module_platform_driver(altr_i2c_driver);
+
+MODULE_DESCRIPTION("Altera Soft IP I2C bus driver");
+MODULE_AUTHOR("Thor Thayer <thor.thayer@linux.intel.com>");
+MODULE_LICENSE("GPL v2");