Patchwork i2c: vt8500: Add support for I2C bus on Wondermedia SoCs

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Submitter Tony Prisk
Date May 12, 2013, 9:23 a.m.
Message ID <1368350634-12654-1-git-send-email-linux@prisktech.co.nz>
Download mbox | patch
Permalink /patch/243162/
State Changes Requested
Headers show

Comments

Tony Prisk - May 12, 2013, 9:23 a.m.
This patch adds support for the I2C bus controllers found on Wondermedia
8xxx-series SoCs. Only master-mode is supported.

Signed-off-by: Tony Prisk <linux@prisktech.co.nz>
---
 .../devicetree/bindings/i2c/i2c-vt8500.txt         |   24 +
 MAINTAINERS                                        |    1 +
 drivers/i2c/busses/Kconfig                         |   10 +
 drivers/i2c/busses/Makefile                        |    1 +
 drivers/i2c/busses/i2c-wmt.c                       |  488 ++++++++++++++++++++
 5 files changed, 524 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/i2c/i2c-vt8500.txt
 create mode 100644 drivers/i2c/busses/i2c-wmt.c
Tony Prisk - May 21, 2013, 6:16 a.m.
On 12/05/13 21:23, Tony Prisk wrote:
> This patch adds support for the I2C bus controllers found on Wondermedia
> 8xxx-series SoCs. Only master-mode is supported.
>
> Signed-off-by: Tony Prisk <linux@prisktech.co.nz>
> ---
>   .../devicetree/bindings/i2c/i2c-vt8500.txt         |   24 +
>   MAINTAINERS                                        |    1 +
>   drivers/i2c/busses/Kconfig                         |   10 +
>   drivers/i2c/busses/Makefile                        |    1 +
>   drivers/i2c/busses/i2c-wmt.c                       |  488 ++++++++++++++++++++
>   5 files changed, 524 insertions(+)
>   create mode 100644 Documentation/devicetree/bindings/i2c/i2c-vt8500.txt
>   create mode 100644 drivers/i2c/busses/i2c-wmt.c
>
>
This patch seems to have stalled. Any news?

Regards
Tony Prisk
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Wolfram Sang - June 10, 2013, 4:03 p.m.
Hi Tony,

> +static int wmt_i2c_wait_bus_not_busy(struct wmt_i2c_dev *i2c_dev)
> diff --git a/drivers/i2c/busses/i2c-wmt.c b/drivers/i2c/busses/i2c-wmt.c
> new file mode 100644
> index 0000000..5cebb29
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-wmt.c

...

> +{
> +	u16 val;
> +	int i;
> +	int ret = 0;
> +
> +	for (i = 0; i < 100000; i++) {
> +		val = readw(i2c_dev->base + REG_CSR);
> +		if (val & CSR_READY_MASK)
> +			break;
> +
> +		udelay(1);
> +	}
> +	if (i >= 9999999)
> +		ret = -EBUSY;

What about using time_after and usleep_range?

> +
> +	return ret;
> +}
> +static int wmt_i2c_write(struct i2c_adapter *adap, struct i2c_msg *pmsg,
> +						   int restart, int last)
> +{
> +	struct wmt_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
> +	u16 val, tcr_val;
> +	int ret, wait_result;
> +	int xfer_len = 0;
> +
> +	if (!restart) {
> +		ret = wmt_i2c_wait_bus_not_busy(i2c_dev);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	if (pmsg->len == 0) {
> +		/*
> +		 * We still need to run through the while (..) once, so
> +		 * start at -1 and break out early from the loop
> +		 */
> +		xfer_len = -1;
> +		writew(0, i2c_dev->base + REG_CDR);
> +	} else {
> +		writew(pmsg->buf[0] & 0xFF, i2c_dev->base + REG_CDR);
> +	}
> +
> +	if (!restart) {
> +		val = readw(i2c_dev->base + REG_CR);
> +		val &= ~CR_TX_END;
> +		writew(val, i2c_dev->base + REG_CR);
> +
> +		val = readw(i2c_dev->base + REG_CR);
> +		val |= CR_CPU_RDY;
> +		writew(val, i2c_dev->base + REG_CR);
> +	}
> +
> +	init_completion(&i2c_dev->complete);

INIT_COMPLETION (and init_completion in probe)

> +static int wmt_i2c_read(struct i2c_adapter *adap, struct i2c_msg *pmsg,
> +						  int restart, int last)
> +{
> +	struct wmt_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
> +	u16 val, tcr_val;
> +	int ret, wait_result;
> +	u32 xfer_len = 0;
> +
> +	if (!restart) {
> +		ret = wmt_i2c_wait_bus_not_busy(i2c_dev);
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	val = readw(i2c_dev->base + REG_CR);
> +	val &= ~CR_TX_END;
> +	writew(val, i2c_dev->base + REG_CR);
> +
> +	val = readw(i2c_dev->base + REG_CR);
> +	val &= ~CR_TX_NEXT_NO_ACK;
> +	writew(val, i2c_dev->base + REG_CR);
> +
> +	if (!restart) {
> +		val = readw(i2c_dev->base + REG_CR);
> +		val |= CR_CPU_RDY;
> +		writew(val, i2c_dev->base + REG_CR);
> +	}
> +
> +	if (pmsg->len == 1) {
> +		val = readw(i2c_dev->base + REG_CR);
> +		val |= CR_TX_NEXT_NO_ACK;
> +		writew(val, i2c_dev->base + REG_CR);
> +	}
> +
> +	init_completion(&i2c_dev->complete);

ditto

> +static int wmt_i2c_xfer(struct i2c_adapter *adap,
> +			struct i2c_msg msgs[],
> +			int num)
> +{
> +	struct i2c_msg *pmsg;
> +	int i, is_last, restart;
> +	int ret = 0;
> +
> +	for (i = 0; ret >= 0 && i < num; i++) {
> +		is_last = ((i + 1) == num);
> +		restart = (i != 0);
> +
> +		pmsg = &msgs[i];
> +		if (pmsg->flags & I2C_M_NOSTART)
> +			restart = 1;

NOSTART is not restart!? Either your variable is misnamed or check
Documentation/i2c/i2c-protocol what it is about.

> +		if (pmsg->flags & I2C_M_RD)
> +			ret = wmt_i2c_read(adap, pmsg, restart, is_last);
> +		else
> +			ret = wmt_i2c_write(adap, pmsg, restart, is_last);
> +	}
> +
> +	return (ret < 0) ? ret : i;
> +}
> +
> +static int wmt_i2c_reset_hardware(struct wmt_i2c_dev *i2c_dev)
> +{
> +	int err;
> +
> +	err = clk_prepare_enable(i2c_dev->clk);
> +	if (err) {
> +		dev_err(i2c_dev->dev, "failed to enable clock\n");
> +		return err;
> +	}
> +
> +	err = clk_set_rate(i2c_dev->clk, 20000000);
> +	if (err) {
> +		dev_err(i2c_dev->dev, "failed to set clock = 20Mhz\n");
> +		return err;
> +	}
> +
> +	writew(0, i2c_dev->base + REG_CR);
> +	writew(12, i2c_dev->base + REG_MCR);

What are those magic values?

> +	writew(ISR_WRITE_ALL, i2c_dev->base + REG_ISR);
> +	writew(IMR_ENABLE_ALL, i2c_dev->base + REG_IMR);
> +	writew(CR_ENABLE, i2c_dev->base + REG_CR);
> +	readw(i2c_dev->base + REG_CSR);		/* read clear */
> +	writew(ISR_WRITE_ALL, i2c_dev->base + REG_ISR);
> +
> +	if (i2c_dev->mode == I2C_MODE_STANDARD)
> +		writew(SCL_TIMEOUT(128) | TR_STD, i2c_dev->base + REG_TR);
> +	else
> +		writew(SCL_TIMEOUT(128) | TR_HS, i2c_dev->base + REG_TR);
> +
> +	return 0;
> +}
> +
> +static int wmt_i2c_probe(struct platform_device *pdev)
> +{
> +	struct device_node *np = pdev->dev.of_node;
> +	struct wmt_i2c_dev *i2c_dev;
> +	struct i2c_adapter *adap;
> +	struct resource *res;
> +	int err;
> +	u32 clk_rate;
> +
> +	if (!np) {
> +		dev_err(&pdev->dev, "device node not found\n");
> +		return -ENODEV;
> +	}

This can't happen since we were matched by the driver core.

> +
> +	i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
> +	if (!i2c_dev) {
> +		dev_err(&pdev->dev, "device memory allocation failed\n");
> +		return -ENOMEM;
> +	}
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	i2c_dev->base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(i2c_dev->base))
> +		return PTR_ERR(i2c_dev->base);
> +
> +	i2c_dev->irq = irq_of_parse_and_map(np, 0);
> +	if (!i2c_dev->irq) {
> +		dev_err(&pdev->dev, "irq missing or invalid\n");
> +		return -EINVAL;
> +	}
> +
> +	i2c_dev->clk = of_clk_get(np, 0);
> +	if (IS_ERR(i2c_dev->clk)) {
> +		dev_err(&pdev->dev, "unable to request clock\n");
> +		return PTR_ERR(i2c_dev->clk);
> +	}
> +
> +	i2c_dev->mode = I2C_MODE_STANDARD;
> +	err = of_property_read_u32(np, "clock-frequency", &clk_rate);
> +	if ((!err) && (clk_rate == 400000))
> +		i2c_dev->mode = I2C_MODE_FAST;
> +
> +	i2c_dev->dev = &pdev->dev;
> +
> +	err = devm_request_irq(&pdev->dev, i2c_dev->irq, wmt_i2c_isr, 0,
> +							"i2c", i2c_dev);
> +	if (err) {
> +		dev_err(&pdev->dev, "failed to request irq %i\n", i2c_dev->irq);
> +		return err;
> +	}
> +
> +	adap = &i2c_dev->adapter;
> +	i2c_set_adapdata(adap, i2c_dev);
> +	strlcpy(adap->name, "WMT I2C adapter", sizeof(adap->name));
> +	adap->owner = THIS_MODULE;
> +	adap->class = I2C_CLASS_HWMON;

Don't use .class unless you have an explicit reason to do so. It may
cost boot-time.

> +	adap->algo = &wmt_i2c_algo;
> +	adap->dev.parent = &pdev->dev;
> +	adap->dev.of_node = pdev->dev.of_node;
> +	adap->nr = of_alias_get_id(pdev->dev.of_node, "i2c");
> +
> +	err = wmt_i2c_reset_hardware(i2c_dev);
> +	if (err) {
> +		dev_err(&pdev->dev, "error initializing hardware\n");
> +		return err;
> +	}
> +
> +	if (adap->nr < 0)
> +		err = i2c_add_adapter(adap);
> +	else
> +		err = i2c_add_numbered_adapter(adap);

add_numbered_adapter does handle this case internally.

> +
> +	if (err) {
> +		dev_err(&pdev->dev, "failed to add adapter\n");
> +		return err;
> +	}
> +
> +	platform_set_drvdata(pdev, i2c_dev);
> +
> +	of_i2c_register_devices(adap);
> +
> +	return 0;
> +}
> +
> +static int wmt_i2c_remove(struct platform_device *pdev)
> +{
> +	struct wmt_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
> +
> +	/* Disable interrupts, clock and delete adapter */
> +	writew(0, i2c_dev->base + REG_IMR);
> +	clk_disable_unprepare(i2c_dev->clk);
> +	i2c_del_adapter(&i2c_dev->adapter);
> +
> +	return 0;
> +}
> +
> +static struct of_device_id wmt_i2c_dt_ids[] = {
> +	{ .compatible = "wm,wm8505-i2c" },
> +	{ /* Sentinel */ },
> +};
> +
> +static struct platform_driver wmt_i2c_driver = {
> +	.probe		= wmt_i2c_probe,
> +	.remove		= wmt_i2c_remove,
> +	.driver		= {
> +		.name	= "wmt-i2c",
> +		.owner	= THIS_MODULE,
> +		.of_match_table = wmt_i2c_dt_ids,
> +	},
> +};
> +
> +module_platform_driver(wmt_i2c_driver);
> +
> +MODULE_DESCRIPTION("Wondermedia I2C master-mode bus adapter");
> +MODULE_AUTHOR("Tony Prisk <linux@prisktech.co.nz>");
> +MODULE_LICENSE("GPL v2");

Header says GPLv2+

> +MODULE_DEVICE_TABLE(of, wmt_i2c_dt_ids);

Thanks,

   Wolfram
Russell King - ARM Linux - June 10, 2013, 11:31 p.m.
On Mon, Jun 10, 2013 at 06:03:29PM +0200, Wolfram Sang wrote:
> Hi Tony,
> 
> > +static int wmt_i2c_wait_bus_not_busy(struct wmt_i2c_dev *i2c_dev)
> > diff --git a/drivers/i2c/busses/i2c-wmt.c b/drivers/i2c/busses/i2c-wmt.c
> > new file mode 100644
> > index 0000000..5cebb29
> > --- /dev/null
> > +++ b/drivers/i2c/busses/i2c-wmt.c
> 
> ...
> 
> > +{
> > +	u16 val;
> > +	int i;
> > +	int ret = 0;
> > +
> > +	for (i = 0; i < 100000; i++) {
> > +		val = readw(i2c_dev->base + REG_CSR);
> > +		if (val & CSR_READY_MASK)
> > +			break;
> > +
> > +		udelay(1);
> > +	}
> > +	if (i >= 9999999)
> > +		ret = -EBUSY;
> 
> What about using time_after and usleep_range?

And in any case this is not the correct way to check for success or
failure.

Failure is defined by readw(i2c_dev->base + REG_CSR) & CSR_READY_MASK
being false.  The above does not check it after the final 1us delay.
You might as well not wait for that final 1us because it's literally
just wasting time the way you've coded it.

Or fix it to re-check for success after the loop completes.
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Patch

diff --git a/Documentation/devicetree/bindings/i2c/i2c-vt8500.txt b/Documentation/devicetree/bindings/i2c/i2c-vt8500.txt
new file mode 100644
index 0000000..94a425e
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/i2c-vt8500.txt
@@ -0,0 +1,24 @@ 
+* Wondermedia I2C Controller
+
+Required properties :
+
+ - compatible : should be "wm,wm8505-i2c"
+ - reg : Offset and length of the register set for the device
+ - interrupts : <IRQ> where IRQ is the interrupt number
+ - clocks : phandle to the I2C clock source
+
+Optional properties :
+
+ - clock-frequency : desired I2C bus clock frequency in Hz.
+	Valid values are 100000 and 400000.
+	Default to 100000 if not specified, or invalid value.
+
+Example :
+
+	i2c_0: i2c@d8280000 {
+		compatible = "wm,wm8505-i2c";
+		reg = <0xd8280000 0x1000>;
+		interrupts = <19>;
+		clocks = <&clki2c0>;
+		clock-frequency = <400000>;
+	};
diff --git a/MAINTAINERS b/MAINTAINERS
index 3d7782b..44ea994 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1285,6 +1285,7 @@  S:	Maintained
 F:	arch/arm/mach-vt8500/
 F:	drivers/clocksource/vt8500_timer.c
 F:	drivers/gpio/gpio-vt8500.c
+F:	drivers/i2c/busses/i2c-wmt.c
 F:	drivers/mmc/host/wmt-sdmmc.c
 F:	drivers/pwm/pwm-vt8500.c
 F:	drivers/rtc/rtc-vt8500.c
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 631736e..89e7ec2 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -724,6 +724,16 @@  config I2C_VERSATILE
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-versatile.
 
+config I2C_WMT
+	tristate "Wondermedia WM8xxx SoC I2C bus support"
+	depends on ARCH_VT8500
+	help
+	  Say yes if you want to support the I2C bus on Wondermedia 8xxx-series
+	  SoCs.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called i2c-wmt.
+
 config I2C_OCTEON
 	tristate "Cavium OCTEON I2C bus support"
 	depends on CPU_CAVIUM_OCTEON
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 8f4fc23..3ba94a9 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -71,6 +71,7 @@  obj-$(CONFIG_I2C_SIRF)		+= i2c-sirf.o
 obj-$(CONFIG_I2C_STU300)	+= i2c-stu300.o
 obj-$(CONFIG_I2C_TEGRA)		+= i2c-tegra.o
 obj-$(CONFIG_I2C_VERSATILE)	+= i2c-versatile.o
+obj-$(CONFIG_I2C_WMT)		+= i2c-wmt.o
 obj-$(CONFIG_I2C_OCTEON)	+= i2c-octeon.o
 obj-$(CONFIG_I2C_XILINX)	+= i2c-xiic.o
 obj-$(CONFIG_I2C_XLR)		+= i2c-xlr.o
diff --git a/drivers/i2c/busses/i2c-wmt.c b/drivers/i2c/busses/i2c-wmt.c
new file mode 100644
index 0000000..5cebb29
--- /dev/null
+++ b/drivers/i2c/busses/i2c-wmt.c
@@ -0,0 +1,488 @@ 
+/*
+ *  Wondermedia I2C Master Mode Driver
+ *
+ *  Copyright (C) 2012 Tony Prisk <linux@prisktech.co.nz>
+ *
+ *  Derived from GPLv2+ licensed source:
+ *  - Copyright (C) 2008 WonderMedia Technologies, Inc.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2, or
+ *  (at your option) any later version. as published by the Free Software
+ *  Foundation
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_i2c.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+
+#define REG_CR		0x00
+#define REG_TCR		0x02
+#define REG_CSR		0x04
+#define REG_ISR		0x06
+#define REG_IMR		0x08
+#define REG_CDR		0x0A
+#define REG_TR		0x0C
+#define REG_MCR		0x0E
+#define REG_SLAVE_CR	0x10
+#define REG_SLAVE_SR	0x12
+#define REG_SLAVE_ISR	0x14
+#define REG_SLAVE_IMR	0x16
+#define REG_SLAVE_DR	0x18
+#define REG_SLAVE_TR	0x1A
+
+/* REG_CR Bit fields */
+#define CR_TX_NEXT_ACK		0x0000
+#define CR_ENABLE		0x0001
+#define CR_TX_NEXT_NO_ACK	0x0002
+#define CR_TX_END		0x0004
+#define CR_CPU_RDY		0x0008
+#define SLAV_MODE_SEL		0x8000
+
+/* REG_TCR Bit fields */
+#define TCR_STANDARD_MODE	0x0000
+#define TCR_MASTER_WRITE	0x0000
+#define TCR_HS_MODE		0x2000
+#define TCR_MASTER_READ		0x4000
+#define TCR_FAST_MODE		0x8000
+#define TCR_SLAVE_ADDR_MASK	0x007F
+
+/* REG_ISR Bit fields */
+#define ISR_NACK_ADDR		0x0001
+#define ISR_BYTE_END		0x0002
+#define ISR_SCL_TIMEOUT		0x0004
+#define ISR_WRITE_ALL		0x0007
+
+/* REG_IMR Bit fields */
+#define IMR_ENABLE_ALL		0x0007
+
+/* REG_CSR Bit fields */
+#define CSR_RCV_NOT_ACK		0x0001
+#define CSR_RCV_ACK_MASK	0x0001
+#define CSR_READY_MASK		0x0002
+
+/* REG_TR */
+#define SCL_TIMEOUT(x)		(((x) & 0xFF) << 16)
+#define TR_STD			0x0064
+#define TR_HS			0x0019
+
+#define I2C_MODE_STANDARD	0
+#define I2C_MODE_FAST		1
+
+struct wmt_i2c_dev {
+	struct i2c_adapter	adapter;
+	struct completion	complete;
+	struct device		*dev;
+	void __iomem		*base;
+	struct clk		*clk;
+	int			mode;
+	int			irq;
+	u16			cmd_status;
+};
+
+static int wmt_i2c_wait_bus_not_busy(struct wmt_i2c_dev *i2c_dev)
+{
+	u16 val;
+	int i;
+	int ret = 0;
+
+	for (i = 0; i < 100000; i++) {
+		val = readw(i2c_dev->base + REG_CSR);
+		if (val & CSR_READY_MASK)
+			break;
+
+		udelay(1);
+	}
+	if (i >= 9999999)
+		ret = -EBUSY;
+
+	return ret;
+}
+
+static int wmt_check_status(struct wmt_i2c_dev *i2c_dev)
+{
+	int ret = 0;
+
+	if (i2c_dev->cmd_status & ISR_NACK_ADDR)
+		ret = -EIO;
+
+	if (i2c_dev->cmd_status & ISR_SCL_TIMEOUT)
+		ret = -ETIMEDOUT;
+
+	return ret;
+}
+
+static int wmt_i2c_write(struct i2c_adapter *adap, struct i2c_msg *pmsg,
+						   int restart, int last)
+{
+	struct wmt_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
+	u16 val, tcr_val;
+	int ret, wait_result;
+	int xfer_len = 0;
+
+	if (!restart) {
+		ret = wmt_i2c_wait_bus_not_busy(i2c_dev);
+		if (ret < 0)
+			return ret;
+	}
+
+	if (pmsg->len == 0) {
+		/*
+		 * We still need to run through the while (..) once, so
+		 * start at -1 and break out early from the loop
+		 */
+		xfer_len = -1;
+		writew(0, i2c_dev->base + REG_CDR);
+	} else {
+		writew(pmsg->buf[0] & 0xFF, i2c_dev->base + REG_CDR);
+	}
+
+	if (!restart) {
+		val = readw(i2c_dev->base + REG_CR);
+		val &= ~CR_TX_END;
+		writew(val, i2c_dev->base + REG_CR);
+
+		val = readw(i2c_dev->base + REG_CR);
+		val |= CR_CPU_RDY;
+		writew(val, i2c_dev->base + REG_CR);
+	}
+
+	init_completion(&i2c_dev->complete);
+
+	if (i2c_dev->mode == I2C_MODE_STANDARD)
+		tcr_val = TCR_STANDARD_MODE;
+	else
+		tcr_val = TCR_FAST_MODE;
+
+	tcr_val |= (TCR_MASTER_WRITE | (pmsg->addr & TCR_SLAVE_ADDR_MASK));
+
+	writew(tcr_val, i2c_dev->base + REG_TCR);
+
+	if (restart) {
+		val = readw(i2c_dev->base + REG_CR);
+		val |= CR_CPU_RDY;
+		writew(val, i2c_dev->base + REG_CR);
+	}
+
+	while (xfer_len < pmsg->len) {
+		wait_result = wait_for_completion_timeout(&i2c_dev->complete,
+							  500 * HZ / 1000);
+
+		if (wait_result == 0)
+			return -ETIMEDOUT;
+
+		ret = wmt_check_status(i2c_dev);
+		if (ret)
+			return ret;
+
+		xfer_len++;
+
+		val = readw(i2c_dev->base + REG_CSR);
+		if ((val & CSR_RCV_ACK_MASK) == CSR_RCV_NOT_ACK) {
+			dev_dbg(i2c_dev->dev, "write RCV NACK error\n");
+			return -EIO;
+		}
+
+		if (pmsg->len == 0) {
+			val = CR_TX_END | CR_CPU_RDY | CR_ENABLE;
+			writew(val, i2c_dev->base + REG_CR);
+			break;
+		}
+
+		if (xfer_len == pmsg->len) {
+			if (last != 1)
+				writew(CR_ENABLE, i2c_dev->base + REG_CR);
+		} else {
+			writew(pmsg->buf[xfer_len] & 0xFF, i2c_dev->base +
+								REG_CDR);
+			writew(CR_CPU_RDY | CR_ENABLE, i2c_dev->base + REG_CR);
+		}
+	}
+
+	return 0;
+}
+
+static int wmt_i2c_read(struct i2c_adapter *adap, struct i2c_msg *pmsg,
+						  int restart, int last)
+{
+	struct wmt_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
+	u16 val, tcr_val;
+	int ret, wait_result;
+	u32 xfer_len = 0;
+
+	if (!restart) {
+		ret = wmt_i2c_wait_bus_not_busy(i2c_dev);
+		if (ret < 0)
+			return ret;
+	}
+
+	val = readw(i2c_dev->base + REG_CR);
+	val &= ~CR_TX_END;
+	writew(val, i2c_dev->base + REG_CR);
+
+	val = readw(i2c_dev->base + REG_CR);
+	val &= ~CR_TX_NEXT_NO_ACK;
+	writew(val, i2c_dev->base + REG_CR);
+
+	if (!restart) {
+		val = readw(i2c_dev->base + REG_CR);
+		val |= CR_CPU_RDY;
+		writew(val, i2c_dev->base + REG_CR);
+	}
+
+	if (pmsg->len == 1) {
+		val = readw(i2c_dev->base + REG_CR);
+		val |= CR_TX_NEXT_NO_ACK;
+		writew(val, i2c_dev->base + REG_CR);
+	}
+
+	init_completion(&i2c_dev->complete);
+
+	if (i2c_dev->mode == I2C_MODE_STANDARD)
+		tcr_val = TCR_STANDARD_MODE;
+	else
+		tcr_val = TCR_FAST_MODE;
+
+	tcr_val |= TCR_MASTER_READ | (pmsg->addr & TCR_SLAVE_ADDR_MASK);
+
+	writew(tcr_val, i2c_dev->base + REG_TCR);
+
+	if (restart) {
+		val = readw(i2c_dev->base + REG_CR);
+		val |= CR_CPU_RDY;
+		writew(val, i2c_dev->base + REG_CR);
+	}
+
+	while (xfer_len < pmsg->len) {
+		wait_result = wait_for_completion_timeout(&i2c_dev->complete,
+							  500 * HZ / 1000);
+
+		if (!wait_result)
+			return -ETIMEDOUT;
+
+		ret = wmt_check_status(i2c_dev);
+		if (ret)
+			return ret;
+
+		pmsg->buf[xfer_len] = readw(i2c_dev->base + REG_CDR) >> 8;
+		xfer_len++;
+
+		if (xfer_len == pmsg->len - 1) {
+			val = readw(i2c_dev->base + REG_CR);
+			val |= (CR_TX_NEXT_NO_ACK | CR_CPU_RDY);
+			writew(val, i2c_dev->base + REG_CR);
+		} else {
+			val = readw(i2c_dev->base + REG_CR);
+			val |= CR_CPU_RDY;
+			writew(val, i2c_dev->base + REG_CR);
+		}
+	}
+
+	return 0;
+}
+
+static int wmt_i2c_xfer(struct i2c_adapter *adap,
+			struct i2c_msg msgs[],
+			int num)
+{
+	struct i2c_msg *pmsg;
+	int i, is_last, restart;
+	int ret = 0;
+
+	for (i = 0; ret >= 0 && i < num; i++) {
+		is_last = ((i + 1) == num);
+		restart = (i != 0);
+
+		pmsg = &msgs[i];
+		if (pmsg->flags & I2C_M_NOSTART)
+			restart = 1;
+		if (pmsg->flags & I2C_M_RD)
+			ret = wmt_i2c_read(adap, pmsg, restart, is_last);
+		else
+			ret = wmt_i2c_write(adap, pmsg, restart, is_last);
+	}
+
+	return (ret < 0) ? ret : i;
+}
+
+static u32 wmt_i2c_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_NOSTART;
+}
+
+static const struct i2c_algorithm wmt_i2c_algo = {
+	.master_xfer	= wmt_i2c_xfer,
+	.functionality	= wmt_i2c_func,
+};
+
+static irqreturn_t wmt_i2c_isr(int irq, void *data)
+{
+	struct wmt_i2c_dev *i2c_dev = data;
+
+	/* save the status and write-clear it */
+	i2c_dev->cmd_status = readw(i2c_dev->base + REG_ISR);
+	writew(i2c_dev->cmd_status, i2c_dev->base + REG_ISR);
+
+	complete(&i2c_dev->complete);
+
+	return IRQ_HANDLED;
+}
+
+static int wmt_i2c_reset_hardware(struct wmt_i2c_dev *i2c_dev)
+{
+	int err;
+
+	err = clk_prepare_enable(i2c_dev->clk);
+	if (err) {
+		dev_err(i2c_dev->dev, "failed to enable clock\n");
+		return err;
+	}
+
+	err = clk_set_rate(i2c_dev->clk, 20000000);
+	if (err) {
+		dev_err(i2c_dev->dev, "failed to set clock = 20Mhz\n");
+		return err;
+	}
+
+	writew(0, i2c_dev->base + REG_CR);
+	writew(12, i2c_dev->base + REG_MCR);
+	writew(ISR_WRITE_ALL, i2c_dev->base + REG_ISR);
+	writew(IMR_ENABLE_ALL, i2c_dev->base + REG_IMR);
+	writew(CR_ENABLE, i2c_dev->base + REG_CR);
+	readw(i2c_dev->base + REG_CSR);		/* read clear */
+	writew(ISR_WRITE_ALL, i2c_dev->base + REG_ISR);
+
+	if (i2c_dev->mode == I2C_MODE_STANDARD)
+		writew(SCL_TIMEOUT(128) | TR_STD, i2c_dev->base + REG_TR);
+	else
+		writew(SCL_TIMEOUT(128) | TR_HS, i2c_dev->base + REG_TR);
+
+	return 0;
+}
+
+static int wmt_i2c_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct wmt_i2c_dev *i2c_dev;
+	struct i2c_adapter *adap;
+	struct resource *res;
+	int err;
+	u32 clk_rate;
+
+	if (!np) {
+		dev_err(&pdev->dev, "device node not found\n");
+		return -ENODEV;
+	}
+
+	i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
+	if (!i2c_dev) {
+		dev_err(&pdev->dev, "device memory allocation failed\n");
+		return -ENOMEM;
+	}
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	i2c_dev->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(i2c_dev->base))
+		return PTR_ERR(i2c_dev->base);
+
+	i2c_dev->irq = irq_of_parse_and_map(np, 0);
+	if (!i2c_dev->irq) {
+		dev_err(&pdev->dev, "irq missing or invalid\n");
+		return -EINVAL;
+	}
+
+	i2c_dev->clk = of_clk_get(np, 0);
+	if (IS_ERR(i2c_dev->clk)) {
+		dev_err(&pdev->dev, "unable to request clock\n");
+		return PTR_ERR(i2c_dev->clk);
+	}
+
+	i2c_dev->mode = I2C_MODE_STANDARD;
+	err = of_property_read_u32(np, "clock-frequency", &clk_rate);
+	if ((!err) && (clk_rate == 400000))
+		i2c_dev->mode = I2C_MODE_FAST;
+
+	i2c_dev->dev = &pdev->dev;
+
+	err = devm_request_irq(&pdev->dev, i2c_dev->irq, wmt_i2c_isr, 0,
+							"i2c", i2c_dev);
+	if (err) {
+		dev_err(&pdev->dev, "failed to request irq %i\n", i2c_dev->irq);
+		return err;
+	}
+
+	adap = &i2c_dev->adapter;
+	i2c_set_adapdata(adap, i2c_dev);
+	strlcpy(adap->name, "WMT I2C adapter", sizeof(adap->name));
+	adap->owner = THIS_MODULE;
+	adap->class = I2C_CLASS_HWMON;
+	adap->algo = &wmt_i2c_algo;
+	adap->dev.parent = &pdev->dev;
+	adap->dev.of_node = pdev->dev.of_node;
+	adap->nr = of_alias_get_id(pdev->dev.of_node, "i2c");
+
+	err = wmt_i2c_reset_hardware(i2c_dev);
+	if (err) {
+		dev_err(&pdev->dev, "error initializing hardware\n");
+		return err;
+	}
+
+	if (adap->nr < 0)
+		err = i2c_add_adapter(adap);
+	else
+		err = i2c_add_numbered_adapter(adap);
+
+	if (err) {
+		dev_err(&pdev->dev, "failed to add adapter\n");
+		return err;
+	}
+
+	platform_set_drvdata(pdev, i2c_dev);
+
+	of_i2c_register_devices(adap);
+
+	return 0;
+}
+
+static int wmt_i2c_remove(struct platform_device *pdev)
+{
+	struct wmt_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
+
+	/* Disable interrupts, clock and delete adapter */
+	writew(0, i2c_dev->base + REG_IMR);
+	clk_disable_unprepare(i2c_dev->clk);
+	i2c_del_adapter(&i2c_dev->adapter);
+
+	return 0;
+}
+
+static struct of_device_id wmt_i2c_dt_ids[] = {
+	{ .compatible = "wm,wm8505-i2c" },
+	{ /* Sentinel */ },
+};
+
+static struct platform_driver wmt_i2c_driver = {
+	.probe		= wmt_i2c_probe,
+	.remove		= wmt_i2c_remove,
+	.driver		= {
+		.name	= "wmt-i2c",
+		.owner	= THIS_MODULE,
+		.of_match_table = wmt_i2c_dt_ids,
+	},
+};
+
+module_platform_driver(wmt_i2c_driver);
+
+MODULE_DESCRIPTION("Wondermedia I2C master-mode bus adapter");
+MODULE_AUTHOR("Tony Prisk <linux@prisktech.co.nz>");
+MODULE_LICENSE("GPL v2");
+MODULE_DEVICE_TABLE(of, wmt_i2c_dt_ids);