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

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>
[wsa: fixed one macro to shift 8 instead of 16]
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-vt8500.txt

+* 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>;
+	};

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

drivers/i2c/busses/Kconfig

@@ -714,6 +714,16 @@ 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

drivers/i2c/busses/Makefile

@@ -70,6 +70,7 @@ 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

drivers/i2c/busses/i2c-wmt.c

+/*
+ *  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) << 8)
+#define TR_STD			0x0064
+#define TR_HS			0x0019
+
+/* REG_MCR */
+#define MCR_APB_96M		7
+#define MCR_APB_166M		12
+
+#define I2C_MODE_STANDARD	0
+#define I2C_MODE_FAST		1
+
+#define WMT_I2C_TIMEOUT		(msecs_to_jiffies(1000))
+
+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)
+{
+	unsigned long timeout;
+
+	timeout = jiffies + WMT_I2C_TIMEOUT;
+	while (!(readw(i2c_dev->base + REG_CSR) & CSR_READY_MASK)) {
+		if (time_after(jiffies, timeout)) {
+			dev_warn(i2c_dev->dev, "timeout waiting for bus ready\n");
+			return -EBUSY;
+		}
+		msleep(20);
+	}
+
+	return 0;
+}
+
+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 last)
+{
+	struct wmt_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
+	u16 val, tcr_val;
+	int ret, wait_result;
+	int xfer_len = 0;
+
+	if (!(pmsg->flags & I2C_M_NOSTART)) {
+		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 (!(pmsg->flags & I2C_M_NOSTART)) {
+		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 (pmsg->flags & I2C_M_NOSTART) {
+		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 last)
+{
+	struct wmt_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
+	u16 val, tcr_val;
+	int ret, wait_result;
+	u32 xfer_len = 0;
+
+	if (!(pmsg->flags & I2C_M_NOSTART)) {
+		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 (!(pmsg->flags & I2C_M_NOSTART)) {
+		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 (pmsg->flags & I2C_M_NOSTART) {
+		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;
+	int ret = 0;
+
+	for (i = 0; ret >= 0 && i < num; i++) {
+		is_last = ((i + 1) == num);
+
+		pmsg = &msgs[i];
+		if (pmsg->flags & I2C_M_RD)
+			ret = wmt_i2c_read(adap, pmsg, is_last);
+		else
+			ret = wmt_i2c_write(adap, pmsg, 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(MCR_APB_166M, 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;
+
+	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->algo = &wmt_i2c_algo;
+	adap->dev.parent = &pdev->dev;
+	adap->dev.of_node = pdev->dev.of_node;
+
+	init_completion(&i2c_dev->complete);
+
+	err = wmt_i2c_reset_hardware(i2c_dev);
+	if (err) {
+		dev_err(&pdev->dev, "error initializing hardware\n");
+		return err;
+	}
+
+	err = i2c_add_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");
+MODULE_DEVICE_TABLE(of, wmt_i2c_dt_ids);