Patchwork [2/4] i2c: Kontron PLD i2c bus driver

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Submitter Kevin Strasser
Date April 8, 2013, 5:15 p.m.
Message ID <1365441321-21952-2-git-send-email-kevin.strasser@linux.intel.com>
Download mbox | patch
Permalink /patch/234845/
State Changes Requested
Headers show

Comments

Kevin Strasser - April 8, 2013, 5:15 p.m.
From: Michael Brunner <michael.brunner@kontron.com>

Add i2c support for the on-board PLD found on some Kontron embedded
modules.

Signed-off-by: Michael Brunner <michael.brunner@kontron.com>
Signed-off-by: Kevin Strasser <kevin.strasser@linux.intel.com>
---
 drivers/i2c/busses/Kconfig      |   20 ++
 drivers/i2c/busses/Makefile     |    1 +
 drivers/i2c/busses/i2c-kempld.c |  679 +++++++++++++++++++++++++++++++++++++++
 drivers/i2c/busses/i2c-kempld.h |   86 +++++
 4 files changed, 786 insertions(+)
 create mode 100644 drivers/i2c/busses/i2c-kempld.c
 create mode 100644 drivers/i2c/busses/i2c-kempld.h
Guenter Roeck - April 10, 2013, 5:02 p.m.
On Mon, Apr 08, 2013 at 10:15:19AM -0700, Kevin Strasser wrote:
> From: Michael Brunner <michael.brunner@kontron.com>
> 
> Add i2c support for the on-board PLD found on some Kontron embedded
> modules.
> 
> Signed-off-by: Michael Brunner <michael.brunner@kontron.com>
> Signed-off-by: Kevin Strasser <kevin.strasser@linux.intel.com>

Overall well written, though I have a couple of nitpicks.

I would prefer two separate drivers, one for the mux and one for the i2c bus.
If that is possible, it would help getting rid of the #ifdef in the code, which
is frowned upon in the kernel.

I dislike unnecessary ( ). Maintainer's call, though.

Couple of places have missing spaces around operators (checkpatch doesn't catch
all those).

As far as I know, devm_ functions are supposed to print an error message on
failure, so it should be unnecessary to print another one if that happens (this
might need some confirmation).

Thanks,
Guenter

> ---
>  drivers/i2c/busses/Kconfig      |   20 ++
>  drivers/i2c/busses/Makefile     |    1 +
>  drivers/i2c/busses/i2c-kempld.c |  679 +++++++++++++++++++++++++++++++++++++++
>  drivers/i2c/busses/i2c-kempld.h |   86 +++++
>  4 files changed, 786 insertions(+)
>  create mode 100644 drivers/i2c/busses/i2c-kempld.c
>  create mode 100644 drivers/i2c/busses/i2c-kempld.h
> 
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index adfee98..7aecd61 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -494,6 +494,26 @@ config I2C_IOP3XX
>  	  This driver can also be built as a module.  If so, the module
>  	  will be called i2c-iop3xx.
>  
> +config I2C_KEMPLD
> +	tristate "Kontron COM I2C"
> +	depends on MFD_KEMPLD
> +	help
> +	  This enables support for the I2C bus interface on some Kontron ETX
> +	  and COMexpress (ETXexpress) modules.
> +
> +	  This driver can also be built as a module. If so, the module
> +	  will be called i2c-kempld.
> +
> +config I2C_KEMPLD_MUX
> +	bool "Enable MUXed I2C ports (EXPERIMENTAL)"
> +	depends on I2C_KEMPLD && I2C_MUX
> +	default n
> +	help
> +	  This enables support for additional I2C ports available on some
> +	  modules. Usually those ports are for board internal usage and
> +	  not routed outside the module.
> +	  Do not use this option unless you know what you are doing!
> +
>  config I2C_MPC
>  	tristate "MPC107/824x/85xx/512x/52xx/83xx/86xx"
>  	depends on PPC
> diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> index 8f4fc23..411b8ce 100644
> --- a/drivers/i2c/busses/Makefile
> +++ b/drivers/i2c/busses/Makefile
> @@ -48,6 +48,7 @@ obj-$(CONFIG_I2C_IBM_IIC)	+= i2c-ibm_iic.o
>  obj-$(CONFIG_I2C_IMX)		+= i2c-imx.o
>  obj-$(CONFIG_I2C_INTEL_MID)	+= i2c-intel-mid.o
>  obj-$(CONFIG_I2C_IOP3XX)	+= i2c-iop3xx.o
> +obj-$(CONFIG_I2C_KEMPLD)    += i2c-kempld.o
>  obj-$(CONFIG_I2C_MPC)		+= i2c-mpc.o
>  obj-$(CONFIG_I2C_MV64XXX)	+= i2c-mv64xxx.o
>  obj-$(CONFIG_I2C_MXS)		+= i2c-mxs.o
> diff --git a/drivers/i2c/busses/i2c-kempld.c b/drivers/i2c/busses/i2c-kempld.c
> new file mode 100644
> index 0000000..c6b44e7
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-kempld.c
> @@ -0,0 +1,679 @@
> +/*
> + *  i2c-kempld.c: I2C bus driver for Kontron COM modules
> + *
> + *  Copyright (c) 2010-2013 Kontron Europe GmbH
> + *  Author: Michael Brunner <michael.brunner@kontron.com>
> + *
> + *  The driver is based on the i2c-ocores driver by Peter Korsgaard.
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License 2 as published
> + *  by the Free Software Foundation.
> + *
> + *  This program is distributed in the hope that 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; see the file COPYING.  If not, write to
> + *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/errno.h>
> +#include <linux/platform_device.h>
> +#include <linux/i2c.h>
> +#ifdef CONFIG_I2C_KEMPLD_MUX
> +#include <linux/i2c-mux.h>
> +#endif
> +#include <linux/delay.h>
> +#include <linux/slab.h>
> +#include <linux/mfd/kempld.h>
> +#include <linux/interrupt.h>
> +#include <linux/time.h>
> +
> +#include "i2c-kempld.h"
> +
> +static int scl_frequency;
> +static int i2c_bus = -1;
> +static int i2c_mx_bus = -1;
> +static bool force_polling;
> +static int i2c_gpio_mux = -1;
> +
> +#ifdef CONFIG_I2C_KEMPLD_MUX
> +static int kempld_i2cmux_select(struct i2c_adapter *adap, void *data, u32 chan)
> +{
> +	struct kempld_i2c_data *i2c = data;
> +	struct kempld_device_data *pld = i2c->pld;
> +	int ret = 0;
> +
> +	if ((i2c->state == STATE_DONE)
> +		|| (i2c->state == STATE_ERROR)) {
> +		if (i2c->mx != chan) {
> +			kempld_get_mutex_set_index(pld, KEMPLD_I2C_MX);
> +			i2c->mx = chan & 0x0f;
> +			kempld_write8(pld, KEMPLD_I2C_MX, i2c->mx);
> +			kempld_release_mutex(pld);
> +		}
> +
> +		/* Reset controller if the last transfer ended with an error */
> +		if (i2c->state == STATE_ERROR) {
> +			u8 ctrl;
> +
> +			kempld_get_mutex_set_index(pld, KEMPLD_I2C_CMD);
> +			ctrl = kempld_read8(pld, KEMPLD_I2C_CONTROL);
> +			ctrl &= ~OCI2C_CTRL_EN;
> +			kempld_write8(pld, KEMPLD_I2C_CONTROL, ctrl);
> +			kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_IACK);
> +			ctrl |= OCI2C_CTRL_EN;
> +			kempld_write8(pld, KEMPLD_I2C_CONTROL, ctrl);
> +			kempld_release_mutex(pld);
> +		}
> +
> +	} else
> +		ret = -EBUSY;
> +
> +	return ret;
> +}
> +
> +static void kempld_i2cmux_del(struct kempld_i2c_data *i2c)
> +{
> +	int i;
> +
> +	for (i = 0; i <= i2c->mx_max; i++) {
> +		if (i2c->mxadap[i]) {
> +			i2c_del_mux_adapter(i2c->mxadap[i]);
> +			i2c->mxadap[i] = NULL;
> +		}
> +	}
> +}
> +
> +static int kempld_i2cmux_add(struct kempld_i2c_data *i2c)
> +{
> +	struct kempld_device_data *pld = i2c->pld;
> +	int i;
> +	int ret = -ENODEV;
> +
> +	for (i = 0; (i <= (i2c->mx_max)); i++) {
> +		i2c->mxadap[i] = i2c_add_mux_adapter(&i2c->adap,
> +							NULL, i2c, 0, i, 0,
> +							kempld_i2cmux_select,
> +							NULL);
> +		if (!i2c->mxadap[i]) {
> +			ret = -ENODEV;
> +			dev_err(pld->dev,
> +				"Failed to register MUX adapter %d\n", i);
> +			goto add_mux_adapter_failed;
> +		}
> +	}
> +
> +	return 0;
> +
> +add_mux_adapter_failed:
> +	kempld_i2cmux_del(i2c);
> +
> +	return ret;
> +}
> +
> +#else
> +#define kempld_i2cmux_add(x) (0)
> +#define kempld_i2cmux_del(x) do {} while (0)
> +#endif
> +
> +static int kempld_i2c_process(struct kempld_i2c_data *i2c)
> +{
> +	struct kempld_device_data *pld = i2c->pld;
> +	struct i2c_msg *msg = i2c->msg;
> +	u8 stat = kempld_read8(pld, KEMPLD_I2C_STATUS);
> +
> +	/* ready? */
> +	if (stat & OCI2C_STAT_TIP)
> +		return -EBUSY;
> +
> +	if ((i2c->state == STATE_DONE) || (i2c->state == STATE_ERROR)) {
> +		/* stop has been sent */
> +		kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_IACK);
> +		if (i2c->irq)
> +			wake_up(&i2c->wait);
> +		if (i2c->state == STATE_ERROR)
> +			return -EIO;
> +		else
> +			return 0;
> +	}
> +
> +	/* error? */
> +	if (stat & OCI2C_STAT_ARBLOST) {
> +		i2c->state = STATE_ERROR;
> +		kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_STOP);
> +		return -EAGAIN;
> +	}
> +
> +	if (i2c->state == STATE_INIT) {
> +		/* check if bus is free */
> +		if (stat & OCI2C_STAT_BUSY)
> +			return -EBUSY;
> +
> +		i2c->state = STATE_ADDR;
> +	}
> +
> +	if (i2c->state == STATE_ADDR) {
> +		u8 addr;
> +		/* 10 bit address? */
> +		if (i2c->msg->flags & I2C_M_TEN) {
> +			addr = 0xf0 | ((i2c->msg->addr >> 7) & 0x6);
> +			i2c->state = STATE_ADDR10;
> +		} else {
> +			addr = (i2c->msg->addr << 1);
> +			i2c->state = STATE_START;
> +		}
> +
> +		/* set read bit if necessary */
> +		addr |= (i2c->msg->flags & I2C_M_RD) ? 1 : 0;
> +
> +		kempld_write8(pld, KEMPLD_I2C_DATA, addr);
> +		kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_START);
> +
> +		return 0;
> +	}
> +
> +	/* second part of 10 bit addressing */
> +	if (i2c->state == STATE_ADDR10) {
> +		kempld_write8(pld, KEMPLD_I2C_DATA, i2c->msg->addr & 0xff);
> +		kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_WRITE);
> +
> +		i2c->state = STATE_START;
> +		return 0;
> +	}
> +
> +	if ((i2c->state == STATE_START) || (i2c->state == STATE_WRITE)) {
> +		i2c->state =
> +			(msg->flags & I2C_M_RD) ? STATE_READ : STATE_WRITE;
> +
> +		if (stat & OCI2C_STAT_NACK) {
> +			i2c->state = STATE_ERROR;
> +			kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_STOP);
> +			return -ENXIO;
> +		}
> +	} else
> +		msg->buf[i2c->pos++] = kempld_read8(pld, KEMPLD_I2C_DATA);
> +
> +	/* end of msg? */
> +	if (i2c->pos >= msg->len) {
> +		i2c->nmsgs--;
> +		i2c->msg++;
> +		i2c->pos = 0;
> +		msg = i2c->msg;
> +
> +		if (i2c->nmsgs) {	/* end? */
> +			/* send start? */
> +			if (!(msg->flags & I2C_M_NOSTART)) {
> +				i2c->state = STATE_ADDR;
> +				if (i2c->irq)
> +					wake_up(&i2c->wait);
> +				return 0;
> +			} else
> +				i2c->state = (msg->flags & I2C_M_RD)
> +					? STATE_READ : STATE_WRITE;
> +		} else {
> +			i2c->state = STATE_DONE;
> +			kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_STOP);
> +			return 0;
> +		}
> +	}
> +
> +	if (i2c->state == STATE_READ) {
> +		kempld_write8(pld, KEMPLD_I2C_CMD, i2c->pos == (msg->len-1) ?
> +			OCI2C_CMD_READ_NACK : OCI2C_CMD_READ_ACK);
> +	} else {
> +		kempld_write8(pld, KEMPLD_I2C_DATA, msg->buf[i2c->pos++]);
> +		kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_WRITE);
> +	}
> +
> +	return 0;
> +}
> +
> +static irqreturn_t kempld_i2c_isr(int irq, void *dev_id)
> +{
> +	struct kempld_i2c_data *i2c = dev_id;
> +
> +	/* The actual ISR handler is put into a tasklet as it may block
> +	 * and therefore rescheduling must be possible */
> +	tasklet_schedule(&i2c->tasklet);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +void kempld_i2c_tasklet(unsigned long data)
> +{
> +	struct kempld_i2c_data *i2c = (struct kempld_i2c_data *)data;
> +	struct kempld_device_data *pld = i2c->pld;
> +
> +	kempld_get_mutex_set_index(pld, KEMPLD_I2C_STATUS);
> +	kempld_i2c_process(i2c);
> +	kempld_release_mutex(pld);
> +}
> +
> +static int kempld_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> +			int num)
> +{
> +	struct kempld_i2c_data *i2c = i2c_get_adapdata(adap);
> +	struct kempld_device_data *pld = i2c->pld;
> +	unsigned long timeout = jiffies + HZ;
> +	int ret;
> +
> +	i2c->msg = msgs;
> +	i2c->pos = 0;
> +	i2c->nmsgs = num;
> +	i2c->state = STATE_INIT;
> +
> +	/* handle the transfer */
> +	while (time_before(jiffies, timeout)) {
> +		kempld_get_mutex_set_index(pld, KEMPLD_I2C_STATUS);
> +		ret = kempld_i2c_process(i2c);
> +		kempld_release_mutex(pld);
> +
> +		if (i2c->irq && ((i2c->state >= STATE_START)
> +				 || (i2c->state == STATE_ERROR))) {
> +			wait_event_timeout(i2c->wait,
> +					(i2c->state == STATE_ERROR) ||
> +					(i2c->state == STATE_DONE) ||
> +					(i2c->state == STATE_ADDR), HZ);
> +			if (i2c->state == STATE_ERROR)
> +				ret = -EIO;
> +		}
> +
> +		if ((i2c->state == STATE_DONE)
> +			|| (i2c->state == STATE_ERROR))
> +			return (i2c->state == STATE_DONE) ? num : ret;
> +
> +		if (ret == 0)
> +			timeout = jiffies + HZ;
> +
> +		usleep_range(5, 15);
> +	}
> +
> +	i2c->state = STATE_ERROR;
> +
> +	return -ETIMEDOUT;
> +}
> +
> +static void kempld_i2c_device_init(struct kempld_i2c_data *i2c)
> +{
> +	struct kempld_device_data *pld = i2c->pld;
> +	long prescale;
> +	u16 prescale_corr;
> +	u8 cfg;
> +	u8 ctrl;
> +	u8 stat;
> +	u8 mx;
> +
> +	kempld_get_mutex_set_index(pld, KEMPLD_I2C_CONTROL);
> +
> +	ctrl = kempld_read8(pld, KEMPLD_I2C_CONTROL);
> +	if (ctrl & OCI2C_CTRL_EN)
> +		i2c->was_active = 1;
> +
> +	/* set bus frequency */
> +	if (scl_frequency > 0) {
> +		/* make sure the device is disabled */
> +		ctrl &= ~(OCI2C_CTRL_EN|OCI2C_CTRL_IEN);
> +		kempld_write8(pld, KEMPLD_I2C_CONTROL, ctrl);
> +
> +		/* The clock frequency calculation has been changed a bit
> +		 * between the spec. revisions */
> +		if (pld->info.spec_major == 1)
> +			prescale = (pld->pld_clock / (scl_frequency*5)) - 1000;
> +		else
> +			prescale = (pld->pld_clock / (scl_frequency*4)) - 3000;
> +
> +		/* Prevent negative prescaler values */
> +		if (prescale < 0)
> +			prescale = 0;
> +
> +		/* Round to the best matching value */
> +		prescale_corr = prescale / 1000;
> +		if ((prescale % 1000) >= 500)
> +			prescale_corr++;
> +
> +		kempld_write8(pld, KEMPLD_I2C_PRELOW, prescale_corr & 0xff);
> +		kempld_write8(pld, KEMPLD_I2C_PREHIGH, prescale_corr >> 8);
> +	}
> +
> +	/* Activate I2C bus output on GPIO pins */
> +	if (i2c_gpio_mux > -1) {
> +		cfg = kempld_read8(pld, KEMPLD_CFG);
> +		if (i2c_gpio_mux)
> +			cfg |= KEMPLD_CFG_GPIO_I2C_MUX;
> +		else
> +			cfg &= ~KEMPLD_CFG_GPIO_I2C_MUX;
> +		kempld_write8(pld, KEMPLD_CFG, cfg);
> +	}
> +	cfg = kempld_read8(pld, KEMPLD_CFG);
> +	if (cfg & KEMPLD_CFG_GPIO_I2C_MUX)
> +		i2c->gpio_mux = 1;
> +	else
> +		i2c->gpio_mux = 0;
> +	if (((i2c_gpio_mux > 0) && (!i2c->gpio_mux))
> +		|| ((i2c_gpio_mux == 0) && (i2c->gpio_mux)))
> +		dev_warn(pld->dev, "Unable to change GPIO I2C MUX setting\n");
> +
> +	/* Check how much multiplexed I2C busses we have */
> +	mx = kempld_read8(pld, KEMPLD_I2C_MX);
> +	if (pld->info.spec_major > 1) {
> +		i2c->mx_max = KEMPLD_I2C_MX_GET_MAX(mx);
> +		if (i2c->mx_max == 0xf) /* No multiplexer available */
> +			i2c->mx_max = 0;
> +	} else
> +		i2c->mx_max = 1;
> +	/* 2 busses should be enough for all
> +	 * boards using specification revision 1 */
> +
> +	/* Check which MX setting should be set */
> +	if ((i2c_mx_bus == -1) || (i2c_mx_bus > i2c->mx_max)) {
> +		if (i2c_mx_bus > i2c->mx_max) {
> +			dev_err(pld->dev,
> +				"bus selected with i2c_mx_bus not available "
> +				"- leaving MX setting unchanged\n");
> +		}
> +		i2c->mx = mx & KEMPLD_I2C_MX_MASK;
> +	} else
> +		i2c->mx = i2c_mx_bus;
> +
> +	/* Connect the controller to the chosen bus output */
> +	kempld_write8(pld, KEMPLD_I2C_MX, i2c->mx);
> +
> +	/* enable the device */
> +	kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_IACK);
> +	ctrl |= OCI2C_CTRL_EN;
> +	kempld_write8(pld, KEMPLD_I2C_CONTROL, ctrl);
> +
> +	/* If bus is busy send a STOP signal to be sure the controller is
> +	 * not hanging... */
> +	stat = kempld_read8(pld, KEMPLD_I2C_STATUS);
> +	if (stat & OCI2C_STAT_BUSY) {
> +		dev_warn(pld->dev,
> +			 "I2C bus is busy - generating stop signal\n");
> +		kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_STOP);
> +	}
> +
> +	kempld_release_mutex(pld);
> +
> +	if ((pld->info.spec_major == 1) && (i2c->mx == 0xf))
> +		i2c->mx = 0;
> +}
> +
> +static void kempld_i2c_irq_enable(struct kempld_i2c_data *i2c)
> +{
> +	struct kempld_device_data *pld = i2c->pld;
> +	u8 irq, ctrl;
> +	int ret;
> +
> +	irq = i2c->irq;
> +
> +	/* This only has to be done once */
> +	if (i2c->irq == 0) {
> +		kempld_get_mutex_set_index(pld, KEMPLD_IRQ_I2C);
> +		irq = kempld_read8(pld, KEMPLD_IRQ_I2C);
> +		kempld_release_mutex(pld);
> +
> +		/* Leave if interrupts are not supported by the I2C core */
> +		if ((irq & 0xf0) == 0xf0)
> +			return;
> +		irq &= 0x0f;
> +		if (irq == 0)
> +			return;
> +
> +		/* Initialize interrupt handlers if not already done */
> +		init_waitqueue_head(&i2c->wait);
> +		tasklet_init(&i2c->tasklet, kempld_i2c_tasklet,
> +				(unsigned long)i2c);
> +
> +		ret = devm_request_irq(pld->dev, irq, kempld_i2c_isr,
> +					IRQF_SHARED, i2c->adap.name, i2c);
> +		if (ret) {
> +			dev_err(pld->dev,
> +				"Unable to claim IRQ - using polling mode\n");
> +			return;
> +		}
> +	}
> +
> +	/* Now enable interrupts in the controller */
> +	kempld_get_mutex_set_index(pld, KEMPLD_I2C_CONTROL);
> +	ctrl = kempld_read8(pld, KEMPLD_I2C_CONTROL);
> +	ctrl |= OCI2C_CTRL_IEN;
> +	kempld_write8(pld, KEMPLD_I2C_CONTROL, ctrl);
> +	kempld_release_mutex(pld);
> +
> +	i2c->irq = irq & 0x0f;
> +}
> +
> +static void kempld_i2c_irq_disable(struct kempld_i2c_data *i2c)
> +{
> +	struct kempld_device_data *pld = i2c->pld;
> +	u8 ctrl;
> +	int irq;
> +
> +	if (i2c->irq == 0)
> +		return;
> +
> +	irq = i2c->irq;
> +	i2c->irq = 0;
> +
> +	tasklet_kill(&i2c->tasklet);
> +
> +	kempld_get_mutex_set_index(pld, KEMPLD_I2C_CONTROL);
> +	ctrl = kempld_read8(pld, KEMPLD_I2C_CONTROL);
> +	ctrl &= ~OCI2C_CTRL_IEN;
> +	kempld_write8(pld, KEMPLD_I2C_CONTROL, ctrl);
> +	kempld_release_mutex(pld);
> +
> +	devm_free_irq(pld->dev, irq, i2c);
> +}
> +
> +static u32 kempld_i2c_func(struct i2c_adapter *adap)
> +{
> +	return I2C_FUNC_I2C | I2C_FUNC_10BIT_ADDR
> +		| I2C_FUNC_SMBUS_EMUL;
> +}
> +
> +static const struct i2c_algorithm kempld_i2c_algorithm = {
> +	.master_xfer	= kempld_i2c_xfer,
> +	.functionality	= kempld_i2c_func,
> +};
> +
> +static struct i2c_adapter kempld_i2c_adapter = {
> +	.owner		= THIS_MODULE,
> +	.name		= "i2c-kempld",
> +	.class		= I2C_CLASS_HWMON | I2C_CLASS_SPD,
> +	.algo		= &kempld_i2c_algorithm,
> +};
> +
> +static int kempld_i2c_get_scl_frequency(struct kempld_i2c_data *i2c)
> +{
> +	struct kempld_device_data *pld = i2c->pld;
> +	int frequency;
> +	u16 prescale;
> +
> +	kempld_get_mutex_set_index(pld, KEMPLD_I2C_PRELOW);
> +
> +	prescale = kempld_read8(pld, KEMPLD_I2C_PRELOW)
> +		| kempld_read8(pld, KEMPLD_I2C_PREHIGH)<<8;
> +
> +	kempld_release_mutex(pld);
> +
> +	/* The clock frequency calculation has been changed a bit
> +	 * between the spec. revisions */
> +	if (pld->info.spec_major == 1)
> +		frequency = (pld->pld_clock / (prescale + 1)) / 5000;
> +	else
> +		frequency = (pld->pld_clock / (prescale + 3)) / 4000;
> +
> +	return frequency;
> +}
> +
> +static int kempld_i2c_probe(struct platform_device *pdev)
> +{
> +	struct kempld_i2c_data *i2c;
> +	struct kempld_device_data *pld;
> +	int ret;
> +
> +	pld = dev_get_drvdata(pdev->dev.parent);
> +
> +	i2c = kzalloc(sizeof(*i2c), GFP_KERNEL);
> +	if (!i2c)
> +		return -ENOMEM;
> +
> +	i2c->pld = pld;
> +
> +	kempld_i2c_device_init(i2c);
> +
> +	/* hook up driver to tree */
> +	platform_set_drvdata(pdev, i2c);
> +	i2c->adap = kempld_i2c_adapter;
> +	i2c_set_adapdata(&i2c->adap, i2c);
> +	i2c->adap.dev.parent = &pdev->dev;
> +
> +	i2c->irq = 0;
> +	if (!force_polling)
> +		kempld_i2c_irq_enable(i2c);
> +
> +	/* add I2C adapter to I2C tree */
> +	i2c->adap.nr = i2c_bus;
> +	ret = i2c_add_numbered_adapter(&i2c->adap);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Failed to add adapter\n");
> +		goto add_adapter_failed;
> +	}
> +
> +	ret = kempld_i2cmux_add(i2c);
> +	if (ret)
> +		goto add_mux_adapters_failed;
> +
> +	dev_info(pld->dev, "I2C bus initialized with %d kHz SCL frequency\n",
> +		 kempld_i2c_get_scl_frequency(i2c));
> +	dev_info(pld->dev, "I2C MUX connected to bus %d (available: %s%d)\n",
> +		 i2c->mx, i2c->mx_max ? "0-" : "", i2c->mx_max);
> +	dev_info(pld->dev, "I2C IRQs %s\n", i2c->irq ? "enabled" : "disabled");
> +	if (i2c->gpio_mux)
> +		dev_info(pld->dev, "GPIO I2C MUX pins enabled\n");
> +
> +	return 0;
> +
> +add_mux_adapters_failed:
> +	i2c_del_adapter(&i2c->adap);
> +add_adapter_failed:
> +	kfree(i2c);
> +
> +	return ret;
> +}
> +
> +static int kempld_i2c_remove(struct platform_device *pdev)
> +{
> +	struct kempld_i2c_data *i2c = platform_get_drvdata(pdev);
> +	struct kempld_device_data *pld = i2c->pld;
> +	u8 ctrl;
> +
> +	kempld_i2c_irq_disable(i2c);
> +
> +	if (!i2c->was_active) {
> +		/* disable I2C logic if it was not activated before the
> +		 * driver loaded */
> +		kempld_get_mutex_set_index(pld, KEMPLD_I2C_CONTROL);
> +		ctrl = kempld_read8(pld, KEMPLD_I2C_CONTROL);
> +		ctrl &= ~OCI2C_CTRL_EN;
> +		kempld_write8(pld, KEMPLD_I2C_CONTROL, ctrl);
> +		kempld_release_mutex(pld);
> +	}
> +
> +	/* remove adapter & data */
> +	kempld_i2cmux_del(i2c);
> +	i2c_del_adapter(&i2c->adap);
> +
> +	platform_set_drvdata(pdev, NULL);
> +
> +	kfree(i2c);
> +
> +	return 0;
> +}
> +
> +#ifdef CONFIG_PM
> +static int kempld_i2c_suspend(struct platform_device *pdev, pm_message_t state)
> +{
> +	struct kempld_i2c_data *i2c = platform_get_drvdata(pdev);
> +	struct kempld_device_data *pld = i2c->pld;
> +	u8 ctrl;
> +
> +	kempld_i2c_irq_disable(i2c);
> +
> +	if (!i2c->was_active) {
> +		/* make sure the device is disabled */
> +		kempld_get_mutex_set_index(pld, KEMPLD_I2C_CONTROL);
> +		ctrl = kempld_read8(pld, KEMPLD_I2C_CONTROL);
> +		ctrl &= ~OCI2C_CTRL_EN;
> +		kempld_write8(pld, KEMPLD_I2C_CONTROL, ctrl);
> +		kempld_release_mutex(pld);
> +	}
> +
> +	return 0;
> +}
> +
> +static int kempld_i2c_resume(struct platform_device *pdev)
> +{
> +	struct kempld_i2c_data *i2c = platform_get_drvdata(pdev);
> +
> +	kempld_i2c_device_init(i2c);
> +	kempld_i2c_irq_enable(i2c);
> +
> +	return 0;
> +}
> +#else
> +#define kempld_i2c_suspend	NULL
> +#define kempld_i2c_resume	NULL
> +#endif
> +
> +static struct platform_driver kempld_i2c_driver = {
> +	.driver = {
> +		.name = "kempld-i2c",
> +		.owner = THIS_MODULE,
> +	},
> +	.probe		= kempld_i2c_probe,
> +	.remove		= kempld_i2c_remove,
> +	.suspend	= kempld_i2c_suspend,
> +	.resume		= kempld_i2c_resume,
> +};
> +
> +static int __init kempld_i2c_init(void)
> +{
> +	/* Check if a valid value for the i2c_mx_bus parameter is provided */
> +	if ((i2c_mx_bus != -1) && (i2c_mx_bus & ~KEMPLD_I2C_MX_MASK))
> +		return -EINVAL;
> +
> +	return platform_driver_register(&kempld_i2c_driver);
> +}
> +
> +static void __exit kempld_i2c_exit(void)
> +{
> +	platform_driver_unregister(&kempld_i2c_driver);
> +}
> +
> +module_init(kempld_i2c_init);
> +module_exit(kempld_i2c_exit);
> +
> +module_param(scl_frequency, int, 0);
> +module_param(i2c_bus, int, 0);
> +module_param(i2c_mx_bus, int, 0);
> +module_param(force_polling, bool, 0);
> +module_param(i2c_gpio_mux, int, 0);
> +
> +MODULE_DESCRIPTION("KEM PLD I2C Driver");
> +MODULE_AUTHOR("Michael Brunner <michael.brunner@kontron.com>");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:kempld_i2c");
> +MODULE_PARM_DESC(scl_frequency, "Set I2C SCL frequency (in kHz) default=0");
> +MODULE_PARM_DESC(i2c_bus, "Set I2C bus (-1 for dynamic assignment");
> +MODULE_PARM_DESC(i2c_mx_bus, "Set I2C MX bus (0-15, default=-1 (FW default))");
> +MODULE_PARM_DESC(force_polling, "Force polling mode");
> +MODULE_PARM_DESC(i2c_gpio_mux, "Enable I2C port on GPIO out");
> diff --git a/drivers/i2c/busses/i2c-kempld.h b/drivers/i2c/busses/i2c-kempld.h
> new file mode 100644
> index 0000000..2229662
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-kempld.h
> @@ -0,0 +1,86 @@
> +/*
> + *  i2c-kempld.h - Kontron PLD I2C driver definitions
> + *
> + *  Copyright (c) 2010-2012 Kontron Europe GmbH
> + *  Author: Michael Brunner <michael.brunner@kontron.com>
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License 2 as published
> + *  by the Free Software Foundation.
> + *
> + *  This program is distributed in the hope that 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; see the file COPYING.  If not, write to
> + *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
> + */
> +
> +#ifndef _KEMPLD_I2C_H_
> +#define _KEMPLD_I2C_H_
> +
> +struct kempld_i2c_data {
> +	struct i2c_adapter		adap;
> +	struct i2c_adapter		*mxadap[15];
> +	struct i2c_msg			*msg;
> +	int				pos;
> +	int				nmsgs;
> +	int				state; /* see STATE_ */
> +	int				was_active;
> +	int				mx;
> +	int				mx_max;
> +	int				gpio_mux;
> +	wait_queue_head_t		wait;
> +	struct tasklet_struct		tasklet;
> +	int				irq;
> +	struct kempld_device_data	*pld;
> +};
> +
> +/* I2C register definitions */
> +#define KEMPLD_I2C_PRELOW	0x0b
> +#define KEMPLD_I2C_PREHIGH	0x0c
> +#define KEMPLD_I2C_CONTROL	0x0d
> +#define KEMPLD_I2C_DATA		0x0e
> +#define KEMPLD_I2C_CMD		0x0f /* write only */
> +#define		KEMPLD_I2C_CMD_STA	0x80
> +#define		KEMPLD_I2C_CMD_STO	0x40
> +#define		KEMPLD_I2C_CMD_RD	0x20
> +#define		KEMPLD_I2C_CMD_WR	0x10
> +#define		KEMPLD_I2C_CMD_NACK	0x08
> +#define		KEMPLD_I2C_CMD_IACK	0x01
> +#define KEMPLD_I2C_STATUS	0x0f /* read only, same address as
> +					KEMPLD_I2C_CMD */
> +#define KEMPLD_I2C_MX		0x15
> +#define		KEMPLD_I2C_MX_GET_MAX(x)	((x & 0xf0)>>4)
> +#define		KEMPLD_I2C_MX_MASK		0x0f
> +
> +#define STATE_DONE		0
> +#define STATE_INIT		1
> +#define STATE_ADDR		2
> +#define STATE_ADDR10		3
> +#define STATE_START		4
> +#define STATE_WRITE		5
> +#define STATE_READ		6
> +#define STATE_ERROR		7
> +
> +/* defines taken from i2c-ocores */
> +#define OCI2C_CTRL_IEN		0x40
> +#define OCI2C_CTRL_EN		0x80
> +
> +#define OCI2C_CMD_START		0x91
> +#define OCI2C_CMD_STOP		0x41
> +#define OCI2C_CMD_READ		0x21
> +#define OCI2C_CMD_WRITE		0x11
> +#define OCI2C_CMD_READ_ACK	0x21
> +#define OCI2C_CMD_READ_NACK	0x29
> +#define OCI2C_CMD_IACK		0x01
> +
> +#define OCI2C_STAT_IF		0x01
> +#define OCI2C_STAT_TIP		0x02
> +#define OCI2C_STAT_ARBLOST	0x20
> +#define OCI2C_STAT_BUSY		0x40
> +#define OCI2C_STAT_NACK		0x80
> +
> +#endif /* _KEMPLD_I2C_H_ */
> -- 
> 1.7.9.5
> 
> --
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> 
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Wolfram Sang - April 16, 2013, 9:53 a.m.
On Wed, Apr 10, 2013 at 10:02:12AM -0700, Guenter Roeck wrote:
> On Mon, Apr 08, 2013 at 10:15:19AM -0700, Kevin Strasser wrote:
> > From: Michael Brunner <michael.brunner@kontron.com>
> > 
> > Add i2c support for the on-board PLD found on some Kontron embedded
> > modules.
> > 
> > Signed-off-by: Michael Brunner <michael.brunner@kontron.com>
> > Signed-off-by: Kevin Strasser <kevin.strasser@linux.intel.com>
> 
> Overall well written, though I have a couple of nitpicks.
> 
> I would prefer two separate drivers, one for the mux and one for the i2c bus.
> If that is possible, it would help getting rid of the #ifdef in the code, which
> is frowned upon in the kernel.
> 
> I dislike unnecessary ( ). Maintainer's call, though.
> 
> Couple of places have missing spaces around operators (checkpatch doesn't catch
> all those).
> 
> As far as I know, devm_ functions are supposed to print an error message on
> failure, so it should be unnecessary to print another one if that happens (this
> might need some confirmation).

Haven't done a full review due to tglx NACK. I agree to the points
mentioned here by Guenter, though.

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Patch

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index adfee98..7aecd61 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -494,6 +494,26 @@  config I2C_IOP3XX
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-iop3xx.
 
+config I2C_KEMPLD
+	tristate "Kontron COM I2C"
+	depends on MFD_KEMPLD
+	help
+	  This enables support for the I2C bus interface on some Kontron ETX
+	  and COMexpress (ETXexpress) modules.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called i2c-kempld.
+
+config I2C_KEMPLD_MUX
+	bool "Enable MUXed I2C ports (EXPERIMENTAL)"
+	depends on I2C_KEMPLD && I2C_MUX
+	default n
+	help
+	  This enables support for additional I2C ports available on some
+	  modules. Usually those ports are for board internal usage and
+	  not routed outside the module.
+	  Do not use this option unless you know what you are doing!
+
 config I2C_MPC
 	tristate "MPC107/824x/85xx/512x/52xx/83xx/86xx"
 	depends on PPC
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 8f4fc23..411b8ce 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -48,6 +48,7 @@  obj-$(CONFIG_I2C_IBM_IIC)	+= i2c-ibm_iic.o
 obj-$(CONFIG_I2C_IMX)		+= i2c-imx.o
 obj-$(CONFIG_I2C_INTEL_MID)	+= i2c-intel-mid.o
 obj-$(CONFIG_I2C_IOP3XX)	+= i2c-iop3xx.o
+obj-$(CONFIG_I2C_KEMPLD)    += i2c-kempld.o
 obj-$(CONFIG_I2C_MPC)		+= i2c-mpc.o
 obj-$(CONFIG_I2C_MV64XXX)	+= i2c-mv64xxx.o
 obj-$(CONFIG_I2C_MXS)		+= i2c-mxs.o
diff --git a/drivers/i2c/busses/i2c-kempld.c b/drivers/i2c/busses/i2c-kempld.c
new file mode 100644
index 0000000..c6b44e7
--- /dev/null
+++ b/drivers/i2c/busses/i2c-kempld.c
@@ -0,0 +1,679 @@ 
+/*
+ *  i2c-kempld.c: I2C bus driver for Kontron COM modules
+ *
+ *  Copyright (c) 2010-2013 Kontron Europe GmbH
+ *  Author: Michael Brunner <michael.brunner@kontron.com>
+ *
+ *  The driver is based on the i2c-ocores driver by Peter Korsgaard.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License 2 as published
+ *  by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that 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; see the file COPYING.  If not, write to
+ *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/errno.h>
+#include <linux/platform_device.h>
+#include <linux/i2c.h>
+#ifdef CONFIG_I2C_KEMPLD_MUX
+#include <linux/i2c-mux.h>
+#endif
+#include <linux/delay.h>
+#include <linux/slab.h>
+#include <linux/mfd/kempld.h>
+#include <linux/interrupt.h>
+#include <linux/time.h>
+
+#include "i2c-kempld.h"
+
+static int scl_frequency;
+static int i2c_bus = -1;
+static int i2c_mx_bus = -1;
+static bool force_polling;
+static int i2c_gpio_mux = -1;
+
+#ifdef CONFIG_I2C_KEMPLD_MUX
+static int kempld_i2cmux_select(struct i2c_adapter *adap, void *data, u32 chan)
+{
+	struct kempld_i2c_data *i2c = data;
+	struct kempld_device_data *pld = i2c->pld;
+	int ret = 0;
+
+	if ((i2c->state == STATE_DONE)
+		|| (i2c->state == STATE_ERROR)) {
+		if (i2c->mx != chan) {
+			kempld_get_mutex_set_index(pld, KEMPLD_I2C_MX);
+			i2c->mx = chan & 0x0f;
+			kempld_write8(pld, KEMPLD_I2C_MX, i2c->mx);
+			kempld_release_mutex(pld);
+		}
+
+		/* Reset controller if the last transfer ended with an error */
+		if (i2c->state == STATE_ERROR) {
+			u8 ctrl;
+
+			kempld_get_mutex_set_index(pld, KEMPLD_I2C_CMD);
+			ctrl = kempld_read8(pld, KEMPLD_I2C_CONTROL);
+			ctrl &= ~OCI2C_CTRL_EN;
+			kempld_write8(pld, KEMPLD_I2C_CONTROL, ctrl);
+			kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_IACK);
+			ctrl |= OCI2C_CTRL_EN;
+			kempld_write8(pld, KEMPLD_I2C_CONTROL, ctrl);
+			kempld_release_mutex(pld);
+		}
+
+	} else
+		ret = -EBUSY;
+
+	return ret;
+}
+
+static void kempld_i2cmux_del(struct kempld_i2c_data *i2c)
+{
+	int i;
+
+	for (i = 0; i <= i2c->mx_max; i++) {
+		if (i2c->mxadap[i]) {
+			i2c_del_mux_adapter(i2c->mxadap[i]);
+			i2c->mxadap[i] = NULL;
+		}
+	}
+}
+
+static int kempld_i2cmux_add(struct kempld_i2c_data *i2c)
+{
+	struct kempld_device_data *pld = i2c->pld;
+	int i;
+	int ret = -ENODEV;
+
+	for (i = 0; (i <= (i2c->mx_max)); i++) {
+		i2c->mxadap[i] = i2c_add_mux_adapter(&i2c->adap,
+							NULL, i2c, 0, i, 0,
+							kempld_i2cmux_select,
+							NULL);
+		if (!i2c->mxadap[i]) {
+			ret = -ENODEV;
+			dev_err(pld->dev,
+				"Failed to register MUX adapter %d\n", i);
+			goto add_mux_adapter_failed;
+		}
+	}
+
+	return 0;
+
+add_mux_adapter_failed:
+	kempld_i2cmux_del(i2c);
+
+	return ret;
+}
+
+#else
+#define kempld_i2cmux_add(x) (0)
+#define kempld_i2cmux_del(x) do {} while (0)
+#endif
+
+static int kempld_i2c_process(struct kempld_i2c_data *i2c)
+{
+	struct kempld_device_data *pld = i2c->pld;
+	struct i2c_msg *msg = i2c->msg;
+	u8 stat = kempld_read8(pld, KEMPLD_I2C_STATUS);
+
+	/* ready? */
+	if (stat & OCI2C_STAT_TIP)
+		return -EBUSY;
+
+	if ((i2c->state == STATE_DONE) || (i2c->state == STATE_ERROR)) {
+		/* stop has been sent */
+		kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_IACK);
+		if (i2c->irq)
+			wake_up(&i2c->wait);
+		if (i2c->state == STATE_ERROR)
+			return -EIO;
+		else
+			return 0;
+	}
+
+	/* error? */
+	if (stat & OCI2C_STAT_ARBLOST) {
+		i2c->state = STATE_ERROR;
+		kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_STOP);
+		return -EAGAIN;
+	}
+
+	if (i2c->state == STATE_INIT) {
+		/* check if bus is free */
+		if (stat & OCI2C_STAT_BUSY)
+			return -EBUSY;
+
+		i2c->state = STATE_ADDR;
+	}
+
+	if (i2c->state == STATE_ADDR) {
+		u8 addr;
+		/* 10 bit address? */
+		if (i2c->msg->flags & I2C_M_TEN) {
+			addr = 0xf0 | ((i2c->msg->addr >> 7) & 0x6);
+			i2c->state = STATE_ADDR10;
+		} else {
+			addr = (i2c->msg->addr << 1);
+			i2c->state = STATE_START;
+		}
+
+		/* set read bit if necessary */
+		addr |= (i2c->msg->flags & I2C_M_RD) ? 1 : 0;
+
+		kempld_write8(pld, KEMPLD_I2C_DATA, addr);
+		kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_START);
+
+		return 0;
+	}
+
+	/* second part of 10 bit addressing */
+	if (i2c->state == STATE_ADDR10) {
+		kempld_write8(pld, KEMPLD_I2C_DATA, i2c->msg->addr & 0xff);
+		kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_WRITE);
+
+		i2c->state = STATE_START;
+		return 0;
+	}
+
+	if ((i2c->state == STATE_START) || (i2c->state == STATE_WRITE)) {
+		i2c->state =
+			(msg->flags & I2C_M_RD) ? STATE_READ : STATE_WRITE;
+
+		if (stat & OCI2C_STAT_NACK) {
+			i2c->state = STATE_ERROR;
+			kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_STOP);
+			return -ENXIO;
+		}
+	} else
+		msg->buf[i2c->pos++] = kempld_read8(pld, KEMPLD_I2C_DATA);
+
+	/* end of msg? */
+	if (i2c->pos >= msg->len) {
+		i2c->nmsgs--;
+		i2c->msg++;
+		i2c->pos = 0;
+		msg = i2c->msg;
+
+		if (i2c->nmsgs) {	/* end? */
+			/* send start? */
+			if (!(msg->flags & I2C_M_NOSTART)) {
+				i2c->state = STATE_ADDR;
+				if (i2c->irq)
+					wake_up(&i2c->wait);
+				return 0;
+			} else
+				i2c->state = (msg->flags & I2C_M_RD)
+					? STATE_READ : STATE_WRITE;
+		} else {
+			i2c->state = STATE_DONE;
+			kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_STOP);
+			return 0;
+		}
+	}
+
+	if (i2c->state == STATE_READ) {
+		kempld_write8(pld, KEMPLD_I2C_CMD, i2c->pos == (msg->len-1) ?
+			OCI2C_CMD_READ_NACK : OCI2C_CMD_READ_ACK);
+	} else {
+		kempld_write8(pld, KEMPLD_I2C_DATA, msg->buf[i2c->pos++]);
+		kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_WRITE);
+	}
+
+	return 0;
+}
+
+static irqreturn_t kempld_i2c_isr(int irq, void *dev_id)
+{
+	struct kempld_i2c_data *i2c = dev_id;
+
+	/* The actual ISR handler is put into a tasklet as it may block
+	 * and therefore rescheduling must be possible */
+	tasklet_schedule(&i2c->tasklet);
+
+	return IRQ_HANDLED;
+}
+
+void kempld_i2c_tasklet(unsigned long data)
+{
+	struct kempld_i2c_data *i2c = (struct kempld_i2c_data *)data;
+	struct kempld_device_data *pld = i2c->pld;
+
+	kempld_get_mutex_set_index(pld, KEMPLD_I2C_STATUS);
+	kempld_i2c_process(i2c);
+	kempld_release_mutex(pld);
+}
+
+static int kempld_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
+			int num)
+{
+	struct kempld_i2c_data *i2c = i2c_get_adapdata(adap);
+	struct kempld_device_data *pld = i2c->pld;
+	unsigned long timeout = jiffies + HZ;
+	int ret;
+
+	i2c->msg = msgs;
+	i2c->pos = 0;
+	i2c->nmsgs = num;
+	i2c->state = STATE_INIT;
+
+	/* handle the transfer */
+	while (time_before(jiffies, timeout)) {
+		kempld_get_mutex_set_index(pld, KEMPLD_I2C_STATUS);
+		ret = kempld_i2c_process(i2c);
+		kempld_release_mutex(pld);
+
+		if (i2c->irq && ((i2c->state >= STATE_START)
+				 || (i2c->state == STATE_ERROR))) {
+			wait_event_timeout(i2c->wait,
+					(i2c->state == STATE_ERROR) ||
+					(i2c->state == STATE_DONE) ||
+					(i2c->state == STATE_ADDR), HZ);
+			if (i2c->state == STATE_ERROR)
+				ret = -EIO;
+		}
+
+		if ((i2c->state == STATE_DONE)
+			|| (i2c->state == STATE_ERROR))
+			return (i2c->state == STATE_DONE) ? num : ret;
+
+		if (ret == 0)
+			timeout = jiffies + HZ;
+
+		usleep_range(5, 15);
+	}
+
+	i2c->state = STATE_ERROR;
+
+	return -ETIMEDOUT;
+}
+
+static void kempld_i2c_device_init(struct kempld_i2c_data *i2c)
+{
+	struct kempld_device_data *pld = i2c->pld;
+	long prescale;
+	u16 prescale_corr;
+	u8 cfg;
+	u8 ctrl;
+	u8 stat;
+	u8 mx;
+
+	kempld_get_mutex_set_index(pld, KEMPLD_I2C_CONTROL);
+
+	ctrl = kempld_read8(pld, KEMPLD_I2C_CONTROL);
+	if (ctrl & OCI2C_CTRL_EN)
+		i2c->was_active = 1;
+
+	/* set bus frequency */
+	if (scl_frequency > 0) {
+		/* make sure the device is disabled */
+		ctrl &= ~(OCI2C_CTRL_EN|OCI2C_CTRL_IEN);
+		kempld_write8(pld, KEMPLD_I2C_CONTROL, ctrl);
+
+		/* The clock frequency calculation has been changed a bit
+		 * between the spec. revisions */
+		if (pld->info.spec_major == 1)
+			prescale = (pld->pld_clock / (scl_frequency*5)) - 1000;
+		else
+			prescale = (pld->pld_clock / (scl_frequency*4)) - 3000;
+
+		/* Prevent negative prescaler values */
+		if (prescale < 0)
+			prescale = 0;
+
+		/* Round to the best matching value */
+		prescale_corr = prescale / 1000;
+		if ((prescale % 1000) >= 500)
+			prescale_corr++;
+
+		kempld_write8(pld, KEMPLD_I2C_PRELOW, prescale_corr & 0xff);
+		kempld_write8(pld, KEMPLD_I2C_PREHIGH, prescale_corr >> 8);
+	}
+
+	/* Activate I2C bus output on GPIO pins */
+	if (i2c_gpio_mux > -1) {
+		cfg = kempld_read8(pld, KEMPLD_CFG);
+		if (i2c_gpio_mux)
+			cfg |= KEMPLD_CFG_GPIO_I2C_MUX;
+		else
+			cfg &= ~KEMPLD_CFG_GPIO_I2C_MUX;
+		kempld_write8(pld, KEMPLD_CFG, cfg);
+	}
+	cfg = kempld_read8(pld, KEMPLD_CFG);
+	if (cfg & KEMPLD_CFG_GPIO_I2C_MUX)
+		i2c->gpio_mux = 1;
+	else
+		i2c->gpio_mux = 0;
+	if (((i2c_gpio_mux > 0) && (!i2c->gpio_mux))
+		|| ((i2c_gpio_mux == 0) && (i2c->gpio_mux)))
+		dev_warn(pld->dev, "Unable to change GPIO I2C MUX setting\n");
+
+	/* Check how much multiplexed I2C busses we have */
+	mx = kempld_read8(pld, KEMPLD_I2C_MX);
+	if (pld->info.spec_major > 1) {
+		i2c->mx_max = KEMPLD_I2C_MX_GET_MAX(mx);
+		if (i2c->mx_max == 0xf) /* No multiplexer available */
+			i2c->mx_max = 0;
+	} else
+		i2c->mx_max = 1;
+	/* 2 busses should be enough for all
+	 * boards using specification revision 1 */
+
+	/* Check which MX setting should be set */
+	if ((i2c_mx_bus == -1) || (i2c_mx_bus > i2c->mx_max)) {
+		if (i2c_mx_bus > i2c->mx_max) {
+			dev_err(pld->dev,
+				"bus selected with i2c_mx_bus not available "
+				"- leaving MX setting unchanged\n");
+		}
+		i2c->mx = mx & KEMPLD_I2C_MX_MASK;
+	} else
+		i2c->mx = i2c_mx_bus;
+
+	/* Connect the controller to the chosen bus output */
+	kempld_write8(pld, KEMPLD_I2C_MX, i2c->mx);
+
+	/* enable the device */
+	kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_IACK);
+	ctrl |= OCI2C_CTRL_EN;
+	kempld_write8(pld, KEMPLD_I2C_CONTROL, ctrl);
+
+	/* If bus is busy send a STOP signal to be sure the controller is
+	 * not hanging... */
+	stat = kempld_read8(pld, KEMPLD_I2C_STATUS);
+	if (stat & OCI2C_STAT_BUSY) {
+		dev_warn(pld->dev,
+			 "I2C bus is busy - generating stop signal\n");
+		kempld_write8(pld, KEMPLD_I2C_CMD, OCI2C_CMD_STOP);
+	}
+
+	kempld_release_mutex(pld);
+
+	if ((pld->info.spec_major == 1) && (i2c->mx == 0xf))
+		i2c->mx = 0;
+}
+
+static void kempld_i2c_irq_enable(struct kempld_i2c_data *i2c)
+{
+	struct kempld_device_data *pld = i2c->pld;
+	u8 irq, ctrl;
+	int ret;
+
+	irq = i2c->irq;
+
+	/* This only has to be done once */
+	if (i2c->irq == 0) {
+		kempld_get_mutex_set_index(pld, KEMPLD_IRQ_I2C);
+		irq = kempld_read8(pld, KEMPLD_IRQ_I2C);
+		kempld_release_mutex(pld);
+
+		/* Leave if interrupts are not supported by the I2C core */
+		if ((irq & 0xf0) == 0xf0)
+			return;
+		irq &= 0x0f;
+		if (irq == 0)
+			return;
+
+		/* Initialize interrupt handlers if not already done */
+		init_waitqueue_head(&i2c->wait);
+		tasklet_init(&i2c->tasklet, kempld_i2c_tasklet,
+				(unsigned long)i2c);
+
+		ret = devm_request_irq(pld->dev, irq, kempld_i2c_isr,
+					IRQF_SHARED, i2c->adap.name, i2c);
+		if (ret) {
+			dev_err(pld->dev,
+				"Unable to claim IRQ - using polling mode\n");
+			return;
+		}
+	}
+
+	/* Now enable interrupts in the controller */
+	kempld_get_mutex_set_index(pld, KEMPLD_I2C_CONTROL);
+	ctrl = kempld_read8(pld, KEMPLD_I2C_CONTROL);
+	ctrl |= OCI2C_CTRL_IEN;
+	kempld_write8(pld, KEMPLD_I2C_CONTROL, ctrl);
+	kempld_release_mutex(pld);
+
+	i2c->irq = irq & 0x0f;
+}
+
+static void kempld_i2c_irq_disable(struct kempld_i2c_data *i2c)
+{
+	struct kempld_device_data *pld = i2c->pld;
+	u8 ctrl;
+	int irq;
+
+	if (i2c->irq == 0)
+		return;
+
+	irq = i2c->irq;
+	i2c->irq = 0;
+
+	tasklet_kill(&i2c->tasklet);
+
+	kempld_get_mutex_set_index(pld, KEMPLD_I2C_CONTROL);
+	ctrl = kempld_read8(pld, KEMPLD_I2C_CONTROL);
+	ctrl &= ~OCI2C_CTRL_IEN;
+	kempld_write8(pld, KEMPLD_I2C_CONTROL, ctrl);
+	kempld_release_mutex(pld);
+
+	devm_free_irq(pld->dev, irq, i2c);
+}
+
+static u32 kempld_i2c_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_10BIT_ADDR
+		| I2C_FUNC_SMBUS_EMUL;
+}
+
+static const struct i2c_algorithm kempld_i2c_algorithm = {
+	.master_xfer	= kempld_i2c_xfer,
+	.functionality	= kempld_i2c_func,
+};
+
+static struct i2c_adapter kempld_i2c_adapter = {
+	.owner		= THIS_MODULE,
+	.name		= "i2c-kempld",
+	.class		= I2C_CLASS_HWMON | I2C_CLASS_SPD,
+	.algo		= &kempld_i2c_algorithm,
+};
+
+static int kempld_i2c_get_scl_frequency(struct kempld_i2c_data *i2c)
+{
+	struct kempld_device_data *pld = i2c->pld;
+	int frequency;
+	u16 prescale;
+
+	kempld_get_mutex_set_index(pld, KEMPLD_I2C_PRELOW);
+
+	prescale = kempld_read8(pld, KEMPLD_I2C_PRELOW)
+		| kempld_read8(pld, KEMPLD_I2C_PREHIGH)<<8;
+
+	kempld_release_mutex(pld);
+
+	/* The clock frequency calculation has been changed a bit
+	 * between the spec. revisions */
+	if (pld->info.spec_major == 1)
+		frequency = (pld->pld_clock / (prescale + 1)) / 5000;
+	else
+		frequency = (pld->pld_clock / (prescale + 3)) / 4000;
+
+	return frequency;
+}
+
+static int kempld_i2c_probe(struct platform_device *pdev)
+{
+	struct kempld_i2c_data *i2c;
+	struct kempld_device_data *pld;
+	int ret;
+
+	pld = dev_get_drvdata(pdev->dev.parent);
+
+	i2c = kzalloc(sizeof(*i2c), GFP_KERNEL);
+	if (!i2c)
+		return -ENOMEM;
+
+	i2c->pld = pld;
+
+	kempld_i2c_device_init(i2c);
+
+	/* hook up driver to tree */
+	platform_set_drvdata(pdev, i2c);
+	i2c->adap = kempld_i2c_adapter;
+	i2c_set_adapdata(&i2c->adap, i2c);
+	i2c->adap.dev.parent = &pdev->dev;
+
+	i2c->irq = 0;
+	if (!force_polling)
+		kempld_i2c_irq_enable(i2c);
+
+	/* add I2C adapter to I2C tree */
+	i2c->adap.nr = i2c_bus;
+	ret = i2c_add_numbered_adapter(&i2c->adap);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to add adapter\n");
+		goto add_adapter_failed;
+	}
+
+	ret = kempld_i2cmux_add(i2c);
+	if (ret)
+		goto add_mux_adapters_failed;
+
+	dev_info(pld->dev, "I2C bus initialized with %d kHz SCL frequency\n",
+		 kempld_i2c_get_scl_frequency(i2c));
+	dev_info(pld->dev, "I2C MUX connected to bus %d (available: %s%d)\n",
+		 i2c->mx, i2c->mx_max ? "0-" : "", i2c->mx_max);
+	dev_info(pld->dev, "I2C IRQs %s\n", i2c->irq ? "enabled" : "disabled");
+	if (i2c->gpio_mux)
+		dev_info(pld->dev, "GPIO I2C MUX pins enabled\n");
+
+	return 0;
+
+add_mux_adapters_failed:
+	i2c_del_adapter(&i2c->adap);
+add_adapter_failed:
+	kfree(i2c);
+
+	return ret;
+}
+
+static int kempld_i2c_remove(struct platform_device *pdev)
+{
+	struct kempld_i2c_data *i2c = platform_get_drvdata(pdev);
+	struct kempld_device_data *pld = i2c->pld;
+	u8 ctrl;
+
+	kempld_i2c_irq_disable(i2c);
+
+	if (!i2c->was_active) {
+		/* disable I2C logic if it was not activated before the
+		 * driver loaded */
+		kempld_get_mutex_set_index(pld, KEMPLD_I2C_CONTROL);
+		ctrl = kempld_read8(pld, KEMPLD_I2C_CONTROL);
+		ctrl &= ~OCI2C_CTRL_EN;
+		kempld_write8(pld, KEMPLD_I2C_CONTROL, ctrl);
+		kempld_release_mutex(pld);
+	}
+
+	/* remove adapter & data */
+	kempld_i2cmux_del(i2c);
+	i2c_del_adapter(&i2c->adap);
+
+	platform_set_drvdata(pdev, NULL);
+
+	kfree(i2c);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int kempld_i2c_suspend(struct platform_device *pdev, pm_message_t state)
+{
+	struct kempld_i2c_data *i2c = platform_get_drvdata(pdev);
+	struct kempld_device_data *pld = i2c->pld;
+	u8 ctrl;
+
+	kempld_i2c_irq_disable(i2c);
+
+	if (!i2c->was_active) {
+		/* make sure the device is disabled */
+		kempld_get_mutex_set_index(pld, KEMPLD_I2C_CONTROL);
+		ctrl = kempld_read8(pld, KEMPLD_I2C_CONTROL);
+		ctrl &= ~OCI2C_CTRL_EN;
+		kempld_write8(pld, KEMPLD_I2C_CONTROL, ctrl);
+		kempld_release_mutex(pld);
+	}
+
+	return 0;
+}
+
+static int kempld_i2c_resume(struct platform_device *pdev)
+{
+	struct kempld_i2c_data *i2c = platform_get_drvdata(pdev);
+
+	kempld_i2c_device_init(i2c);
+	kempld_i2c_irq_enable(i2c);
+
+	return 0;
+}
+#else
+#define kempld_i2c_suspend	NULL
+#define kempld_i2c_resume	NULL
+#endif
+
+static struct platform_driver kempld_i2c_driver = {
+	.driver = {
+		.name = "kempld-i2c",
+		.owner = THIS_MODULE,
+	},
+	.probe		= kempld_i2c_probe,
+	.remove		= kempld_i2c_remove,
+	.suspend	= kempld_i2c_suspend,
+	.resume		= kempld_i2c_resume,
+};
+
+static int __init kempld_i2c_init(void)
+{
+	/* Check if a valid value for the i2c_mx_bus parameter is provided */
+	if ((i2c_mx_bus != -1) && (i2c_mx_bus & ~KEMPLD_I2C_MX_MASK))
+		return -EINVAL;
+
+	return platform_driver_register(&kempld_i2c_driver);
+}
+
+static void __exit kempld_i2c_exit(void)
+{
+	platform_driver_unregister(&kempld_i2c_driver);
+}
+
+module_init(kempld_i2c_init);
+module_exit(kempld_i2c_exit);
+
+module_param(scl_frequency, int, 0);
+module_param(i2c_bus, int, 0);
+module_param(i2c_mx_bus, int, 0);
+module_param(force_polling, bool, 0);
+module_param(i2c_gpio_mux, int, 0);
+
+MODULE_DESCRIPTION("KEM PLD I2C Driver");
+MODULE_AUTHOR("Michael Brunner <michael.brunner@kontron.com>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:kempld_i2c");
+MODULE_PARM_DESC(scl_frequency, "Set I2C SCL frequency (in kHz) default=0");
+MODULE_PARM_DESC(i2c_bus, "Set I2C bus (-1 for dynamic assignment");
+MODULE_PARM_DESC(i2c_mx_bus, "Set I2C MX bus (0-15, default=-1 (FW default))");
+MODULE_PARM_DESC(force_polling, "Force polling mode");
+MODULE_PARM_DESC(i2c_gpio_mux, "Enable I2C port on GPIO out");
diff --git a/drivers/i2c/busses/i2c-kempld.h b/drivers/i2c/busses/i2c-kempld.h
new file mode 100644
index 0000000..2229662
--- /dev/null
+++ b/drivers/i2c/busses/i2c-kempld.h
@@ -0,0 +1,86 @@ 
+/*
+ *  i2c-kempld.h - Kontron PLD I2C driver definitions
+ *
+ *  Copyright (c) 2010-2012 Kontron Europe GmbH
+ *  Author: Michael Brunner <michael.brunner@kontron.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License 2 as published
+ *  by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that 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; see the file COPYING.  If not, write to
+ *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef _KEMPLD_I2C_H_
+#define _KEMPLD_I2C_H_
+
+struct kempld_i2c_data {
+	struct i2c_adapter		adap;
+	struct i2c_adapter		*mxadap[15];
+	struct i2c_msg			*msg;
+	int				pos;
+	int				nmsgs;
+	int				state; /* see STATE_ */
+	int				was_active;
+	int				mx;
+	int				mx_max;
+	int				gpio_mux;
+	wait_queue_head_t		wait;
+	struct tasklet_struct		tasklet;
+	int				irq;
+	struct kempld_device_data	*pld;
+};
+
+/* I2C register definitions */
+#define KEMPLD_I2C_PRELOW	0x0b
+#define KEMPLD_I2C_PREHIGH	0x0c
+#define KEMPLD_I2C_CONTROL	0x0d
+#define KEMPLD_I2C_DATA		0x0e
+#define KEMPLD_I2C_CMD		0x0f /* write only */
+#define		KEMPLD_I2C_CMD_STA	0x80
+#define		KEMPLD_I2C_CMD_STO	0x40
+#define		KEMPLD_I2C_CMD_RD	0x20
+#define		KEMPLD_I2C_CMD_WR	0x10
+#define		KEMPLD_I2C_CMD_NACK	0x08
+#define		KEMPLD_I2C_CMD_IACK	0x01
+#define KEMPLD_I2C_STATUS	0x0f /* read only, same address as
+					KEMPLD_I2C_CMD */
+#define KEMPLD_I2C_MX		0x15
+#define		KEMPLD_I2C_MX_GET_MAX(x)	((x & 0xf0)>>4)
+#define		KEMPLD_I2C_MX_MASK		0x0f
+
+#define STATE_DONE		0
+#define STATE_INIT		1
+#define STATE_ADDR		2
+#define STATE_ADDR10		3
+#define STATE_START		4
+#define STATE_WRITE		5
+#define STATE_READ		6
+#define STATE_ERROR		7
+
+/* defines taken from i2c-ocores */
+#define OCI2C_CTRL_IEN		0x40
+#define OCI2C_CTRL_EN		0x80
+
+#define OCI2C_CMD_START		0x91
+#define OCI2C_CMD_STOP		0x41
+#define OCI2C_CMD_READ		0x21
+#define OCI2C_CMD_WRITE		0x11
+#define OCI2C_CMD_READ_ACK	0x21
+#define OCI2C_CMD_READ_NACK	0x29
+#define OCI2C_CMD_IACK		0x01
+
+#define OCI2C_STAT_IF		0x01
+#define OCI2C_STAT_TIP		0x02
+#define OCI2C_STAT_ARBLOST	0x20
+#define OCI2C_STAT_BUSY		0x40
+#define OCI2C_STAT_NACK		0x80
+
+#endif /* _KEMPLD_I2C_H_ */