i2c: add support for the Digicolor I2C controller

The CX92755 is an SoC in the Conexant Digicolor series. The devicetree binding
document describes the I2C controller on the CX92755 SoC, that is also shared
by some other SoCs in the Digicolor series. The driver adds support.
Signed-off-by: NBaruch Siach <baruch@tkos.co.il>
[wsa: fixed spaces around operators]
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

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

+Conexant Digicolor I2C controller
+
+Required properties:
+ - compatible: must be "cnxt,cx92755-i2c"
+ - reg: physical address and length of the device registers
+ - interrupts: a single interrupt specifier
+ - clocks: clock for the device
+ - #address-cells: should be <1>
+ - #size-cells: should be <0>
+
+Optional properties:
+- clock-frequency: the desired I2C bus clock frequency in Hz; in
+  absence of this property the default value is used (100 kHz).
+
+Example:
+
+	i2c: i2c@f0000120 {
+		compatible = "cnxt,cx92755-i2c";
+		reg = <0xf0000120 0x10>;
+		interrupts = <28>;
+		clocks = <&main_clk>;
+		clock-frequency = <100000>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+	};

drivers/i2c/busses/Kconfig

@@ -485,6 +485,15 @@ config I2C_DESIGNWARE_BAYTRAIL
 	  the platform firmware controlling it. You should say Y if running on
 	  a BayTrail system using the AXP288.
 
+config I2C_DIGICOLOR
+	tristate "Conexant Digicolor I2C driver"
+	depends on ARCH_DIGICOLOR
+	help
+	  Support for Conexant Digicolor SoCs (CX92755) I2C controller driver.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called i2c-digicolor.
+
 config I2C_EFM32
 	tristate "EFM32 I2C controller"
 	depends on ARCH_EFM32 || COMPILE_TEST

drivers/i2c/busses/Makefile

@@ -45,6 +45,7 @@ i2c-designware-platform-objs := i2c-designware-platdrv.o
 i2c-designware-platform-$(CONFIG_I2C_DESIGNWARE_BAYTRAIL) += i2c-designware-baytrail.o
 obj-$(CONFIG_I2C_DESIGNWARE_PCI)	+= i2c-designware-pci.o
 i2c-designware-pci-objs := i2c-designware-pcidrv.o
+obj-$(CONFIG_I2C_DIGICOLOR)	+= i2c-digicolor.o
 obj-$(CONFIG_I2C_EFM32)		+= i2c-efm32.o
 obj-$(CONFIG_I2C_EG20T)		+= i2c-eg20t.o
 obj-$(CONFIG_I2C_EXYNOS5)	+= i2c-exynos5.o

drivers/i2c/busses/i2c-digicolor.c

+/*
+ * I2C bus driver for Conexant Digicolor SoCs
+ *
+ * Author: Baruch Siach <baruch@tkos.co.il>
+ *
+ * Copyright (C) 2015 Paradox Innovation Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/clk.h>
+#include <linux/completion.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+#define DEFAULT_FREQ		100000
+#define TIMEOUT_MS		100
+
+#define II_CONTROL		0x0
+#define II_CONTROL_LOCAL_RESET	BIT(0)
+
+#define II_CLOCKTIME		0x1
+
+#define II_COMMAND		0x2
+#define II_CMD_START		1
+#define II_CMD_RESTART		2
+#define II_CMD_SEND_ACK		3
+#define II_CMD_GET_ACK		6
+#define II_CMD_GET_NOACK	7
+#define II_CMD_STOP		10
+#define II_COMMAND_GO		BIT(7)
+#define II_COMMAND_COMPLETION_STATUS(r)	(((r) >> 5) & 3)
+#define II_CMD_STATUS_NORMAL	0
+#define II_CMD_STATUS_ACK_GOOD	1
+#define II_CMD_STATUS_ACK_BAD	2
+#define II_CMD_STATUS_ABORT	3
+
+#define II_DATA			0x3
+#define II_INTFLAG_CLEAR	0x8
+#define II_INTENABLE		0xa
+
+struct dc_i2c {
+	struct i2c_adapter	adap;
+	struct device		*dev;
+	void __iomem		*regs;
+	struct clk		*clk;
+	unsigned int		frequency;
+
+	struct i2c_msg		*msg;
+	unsigned int		msgbuf_ptr;
+	int			last;
+	spinlock_t		lock;
+	struct completion	done;
+	int			state;
+	int			error;
+};
+
+enum {
+	STATE_IDLE,
+	STATE_START,
+	STATE_ADDR,
+	STATE_WRITE,
+	STATE_READ,
+	STATE_STOP,
+};
+
+static void dc_i2c_cmd(struct dc_i2c *i2c, u8 cmd)
+{
+	writeb_relaxed(cmd | II_COMMAND_GO, i2c->regs + II_COMMAND);
+}
+
+static u8 dc_i2c_addr_cmd(struct i2c_msg *msg)
+{
+	u8 addr = (msg->addr & 0x7f) << 1;
+
+	if (msg->flags & I2C_M_RD)
+		addr |= 1;
+
+	return addr;
+}
+
+static void dc_i2c_data(struct dc_i2c *i2c, u8 data)
+{
+	writeb_relaxed(data, i2c->regs + II_DATA);
+}
+
+static void dc_i2c_write_byte(struct dc_i2c *i2c, u8 byte)
+{
+	dc_i2c_data(i2c, byte);
+	dc_i2c_cmd(i2c, II_CMD_SEND_ACK);
+}
+
+static void dc_i2c_write_buf(struct dc_i2c *i2c)
+{
+	dc_i2c_write_byte(i2c, i2c->msg->buf[i2c->msgbuf_ptr++]);
+}
+
+static void dc_i2c_next_read(struct dc_i2c *i2c)
+{
+	bool last = (i2c->msgbuf_ptr + 1 == i2c->msg->len);
+
+	dc_i2c_cmd(i2c, last ? II_CMD_GET_NOACK : II_CMD_GET_ACK);
+}
+
+static void dc_i2c_stop(struct dc_i2c *i2c)
+{
+	i2c->state = STATE_STOP;
+	if (i2c->last)
+		dc_i2c_cmd(i2c, II_CMD_STOP);
+	else
+		complete(&i2c->done);
+}
+
+static u8 dc_i2c_read_byte(struct dc_i2c *i2c)
+{
+	return readb_relaxed(i2c->regs + II_DATA);
+}
+
+static void dc_i2c_read_buf(struct dc_i2c *i2c)
+{
+	i2c->msg->buf[i2c->msgbuf_ptr++] = dc_i2c_read_byte(i2c);
+	dc_i2c_next_read(i2c);
+}
+
+static void dc_i2c_set_irq(struct dc_i2c *i2c, int enable)
+{
+	if (enable)
+		writeb_relaxed(1, i2c->regs + II_INTFLAG_CLEAR);
+	writeb_relaxed(!!enable, i2c->regs + II_INTENABLE);
+}
+
+static int dc_i2c_cmd_status(struct dc_i2c *i2c)
+{
+	u8 cmd = readb_relaxed(i2c->regs + II_COMMAND);
+
+	return II_COMMAND_COMPLETION_STATUS(cmd);
+}
+
+static void dc_i2c_start_msg(struct dc_i2c *i2c, int first)
+{
+	struct i2c_msg *msg = i2c->msg;
+
+	if (!(msg->flags & I2C_M_NOSTART)) {
+		i2c->state = STATE_START;
+		dc_i2c_cmd(i2c, first ? II_CMD_START : II_CMD_RESTART);
+	} else if (msg->flags & I2C_M_RD) {
+		i2c->state = STATE_READ;
+		dc_i2c_next_read(i2c);
+	} else {
+		i2c->state = STATE_WRITE;
+		dc_i2c_write_buf(i2c);
+	}
+}
+
+static irqreturn_t dc_i2c_irq(int irq, void *dev_id)
+{
+	struct dc_i2c *i2c = dev_id;
+	int cmd_status = dc_i2c_cmd_status(i2c);
+	unsigned long flags;
+	u8 addr_cmd;
+
+	writeb_relaxed(1, i2c->regs + II_INTFLAG_CLEAR);
+
+	spin_lock_irqsave(&i2c->lock, flags);
+
+	if (cmd_status == II_CMD_STATUS_ACK_BAD
+	    || cmd_status == II_CMD_STATUS_ABORT) {
+		i2c->error = -EIO;
+		complete(&i2c->done);
+		goto out;
+	}
+
+	switch (i2c->state) {
+	case STATE_START:
+		addr_cmd = dc_i2c_addr_cmd(i2c->msg);
+		dc_i2c_write_byte(i2c, addr_cmd);
+		i2c->state = STATE_ADDR;
+		break;
+	case STATE_ADDR:
+		if (i2c->msg->flags & I2C_M_RD) {
+			dc_i2c_next_read(i2c);
+			i2c->state = STATE_READ;
+			break;
+		}
+		i2c->state = STATE_WRITE;
+		/* fall through */
+	case STATE_WRITE:
+		if (i2c->msgbuf_ptr < i2c->msg->len)
+			dc_i2c_write_buf(i2c);
+		else
+			dc_i2c_stop(i2c);
+		break;
+	case STATE_READ:
+		if (i2c->msgbuf_ptr < i2c->msg->len)
+			dc_i2c_read_buf(i2c);
+		else
+			dc_i2c_stop(i2c);
+		break;
+	case STATE_STOP:
+		i2c->state = STATE_IDLE;
+		complete(&i2c->done);
+		break;
+	}
+
+out:
+	spin_unlock_irqrestore(&i2c->lock, flags);
+	return IRQ_HANDLED;
+}
+
+static int dc_i2c_xfer_msg(struct dc_i2c *i2c, struct i2c_msg *msg, int first,
+			   int last)
+{
+	unsigned long timeout = msecs_to_jiffies(TIMEOUT_MS);
+	unsigned long flags;
+
+	spin_lock_irqsave(&i2c->lock, flags);
+	i2c->msg = msg;
+	i2c->msgbuf_ptr = 0;
+	i2c->last = last;
+	i2c->error = 0;
+
+	reinit_completion(&i2c->done);
+	dc_i2c_set_irq(i2c, 1);
+	dc_i2c_start_msg(i2c, first);
+	spin_unlock_irqrestore(&i2c->lock, flags);
+
+	timeout = wait_for_completion_timeout(&i2c->done, timeout);
+	dc_i2c_set_irq(i2c, 0);
+	if (timeout == 0) {
+		i2c->state = STATE_IDLE;
+		return -ETIMEDOUT;
+	}
+
+	if (i2c->error)
+		return i2c->error;
+
+	return 0;
+}
+
+static int dc_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
+{
+	struct dc_i2c *i2c = adap->algo_data;
+	int i, ret;
+
+	for (i = 0; i < num; i++) {
+		ret = dc_i2c_xfer_msg(i2c, &msgs[i], i == 0, i == num - 1);
+		if (ret)
+			return ret;
+	}
+
+	return num;
+}
+
+static int dc_i2c_init_hw(struct dc_i2c *i2c)
+{
+	unsigned long clk_rate = clk_get_rate(i2c->clk);
+	unsigned int clocktime;
+
+	writeb_relaxed(II_CONTROL_LOCAL_RESET, i2c->regs + II_CONTROL);
+	udelay(100);
+	writeb_relaxed(0, i2c->regs + II_CONTROL);
+	udelay(100);
+
+	clocktime = DIV_ROUND_UP(clk_rate, 64 * i2c->frequency);
+	if (clocktime < 1 || clocktime > 0xff) {
+		dev_err(i2c->dev, "can't set bus speed of %u Hz\n",
+			i2c->frequency);
+		return -EINVAL;
+	}
+	writeb_relaxed(clocktime - 1, i2c->regs + II_CLOCKTIME);
+
+	return 0;
+}
+
+static u32 dc_i2c_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_NOSTART;
+}
+
+static const struct i2c_algorithm dc_i2c_algorithm = {
+	.master_xfer	= dc_i2c_xfer,
+	.functionality	= dc_i2c_func,
+};
+
+static int dc_i2c_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct dc_i2c *i2c;
+	struct resource *r;
+	int ret = 0, irq;
+
+	i2c = devm_kzalloc(&pdev->dev, sizeof(struct dc_i2c), GFP_KERNEL);
+	if (!i2c)
+		return -ENOMEM;
+
+	if (of_property_read_u32(pdev->dev.of_node, "clock-frequency",
+				 &i2c->frequency))
+		i2c->frequency = DEFAULT_FREQ;
+
+	i2c->dev = &pdev->dev;
+	platform_set_drvdata(pdev, i2c);
+
+	spin_lock_init(&i2c->lock);
+	init_completion(&i2c->done);
+
+	i2c->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(i2c->clk))
+		return PTR_ERR(i2c->clk);
+
+	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	i2c->regs = devm_ioremap_resource(&pdev->dev, r);
+	if (IS_ERR(i2c->regs))
+		return PTR_ERR(i2c->regs);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	ret = devm_request_irq(&pdev->dev, irq, dc_i2c_irq, 0,
+			       dev_name(&pdev->dev), i2c);
+	if (ret < 0)
+		return ret;
+
+	strlcpy(i2c->adap.name, "Conexant Digicolor I2C adapter",
+		sizeof(i2c->adap.name));
+	i2c->adap.owner = THIS_MODULE;
+	i2c->adap.algo = &dc_i2c_algorithm;
+	i2c->adap.dev.parent = &pdev->dev;
+	i2c->adap.dev.of_node = np;
+	i2c->adap.algo_data = i2c;
+
+	ret = dc_i2c_init_hw(i2c);
+	if (ret)
+		return ret;
+
+	ret = clk_prepare_enable(i2c->clk);
+	if (ret < 0)
+		return ret;
+
+	ret = i2c_add_adapter(&i2c->adap);
+	if (ret < 0) {
+		clk_unprepare(i2c->clk);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int dc_i2c_remove(struct platform_device *pdev)
+{
+	struct dc_i2c *i2c = platform_get_drvdata(pdev);
+
+	i2c_del_adapter(&i2c->adap);
+	clk_disable_unprepare(i2c->clk);
+
+	return 0;
+}
+
+static const struct of_device_id dc_i2c_match[] = {
+	{ .compatible = "cnxt,cx92755-i2c" },
+	{ },
+};
+
+static struct platform_driver dc_i2c_driver = {
+	.probe   = dc_i2c_probe,
+	.remove  = dc_i2c_remove,
+	.driver  = {
+		.name  = "digicolor-i2c",
+		.of_match_table = dc_i2c_match,
+	},
+};
+module_platform_driver(dc_i2c_driver);
+
+MODULE_AUTHOR("Baruch Siach <baruch@tkos.co.il>");
+MODULE_DESCRIPTION("Conexant Digicolor I2C master driver");
+MODULE_LICENSE("GPL v2");