i2c: add support for Amlogic Meson I2C controller

This is a driver for the I2C controller found in Amlogic Meson SoCs.

Signed-off-by: Beniamino Galvani <[e-mail]>
Signed-off-by: Wolfram Sang <[e-mail]>

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

···
+Amlogic Meson I2C controller
+
+Required properties:
+ - compatible: must be "amlogic,meson6-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).
+
+Examples:
+
+	i2c@c8100500 {
+		compatible = "amlogic,meson6-i2c";
+		reg = <0xc8100500 0x20>;
+		interrupts = <0 92 1>;
+		clocks = <&clk81>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+	};

drivers/i2c/busses/Kconfig

···
 	  This driver can also be built as a module. If so, the module
 	  will be called i2c-kempld.
 
+config I2C_MESON
+	tristate "Amlogic Meson I2C controller"
+	depends on ARCH_MESON
+	help
+	  If you say yes to this option, support will be included for the
+	  I2C interface on the Amlogic Meson family of SoCs.
+
 config I2C_MPC
 	tristate "MPC107/824x/85xx/512x/52xx/83xx/86xx"
 	depends on PPC

drivers/i2c/busses/Makefile

···
 obj-$(CONFIG_I2C_IMX)		+= i2c-imx.o
 obj-$(CONFIG_I2C_IOP3XX)	+= i2c-iop3xx.o
 obj-$(CONFIG_I2C_KEMPLD)	+= i2c-kempld.o
+obj-$(CONFIG_I2C_MESON)		+= i2c-meson.o
 obj-$(CONFIG_I2C_MPC)		+= i2c-mpc.o
 obj-$(CONFIG_I2C_MV64XXX)	+= i2c-mv64xxx.o
 obj-$(CONFIG_I2C_MXS)		+= i2c-mxs.o

drivers/i2c/busses/i2c-meson.c

···
+/*
+ * I2C bus driver for Amlogic Meson SoCs
+ *
+ * Copyright (C) 2014 Beniamino Galvani <[e-mail]>
+ *
+ * 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/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+
+/* Meson I2C register map */
+#define REG_CTRL		0x00
+#define REG_SLAVE_ADDR		0x04
+#define REG_TOK_LIST0		0x08
+#define REG_TOK_LIST1		0x0c
+#define REG_TOK_WDATA0		0x10
+#define REG_TOK_WDATA1		0x14
+#define REG_TOK_RDATA0		0x18
+#define REG_TOK_RDATA1		0x1c
+
+/* Control register fields */
+#define REG_CTRL_START		BIT(0)
+#define REG_CTRL_ACK_IGNORE	BIT(1)
+#define REG_CTRL_STATUS		BIT(2)
+#define REG_CTRL_ERROR		BIT(3)
+#define REG_CTRL_CLKDIV_SHIFT	12
+#define REG_CTRL_CLKDIV_MASK	((BIT(10) - 1) << REG_CTRL_CLKDIV_SHIFT)
+
+#define I2C_TIMEOUT_MS		500
+#define DEFAULT_FREQ		100000
+
+enum {
+	TOKEN_END = 0,
+	TOKEN_START,
+	TOKEN_SLAVE_ADDR_WRITE,
+	TOKEN_SLAVE_ADDR_READ,
+	TOKEN_DATA,
+	TOKEN_DATA_LAST,
+	TOKEN_STOP,
+};
+
+enum {
+	STATE_IDLE,
+	STATE_READ,
+	STATE_WRITE,
+	STATE_STOP,
+};
+
+/**
+ * struct meson_i2c - Meson I2C device private data
+ *
+ * @adap:	I2C adapter instance
+ * @dev:	Pointer to device structure
+ * @regs:	Base address of the device memory mapped registers
+ * @clk:	Pointer to clock structure
+ * @irq:	IRQ number
+ * @msg:	Pointer to the current I2C message
+ * @state:	Current state in the driver state machine
+ * @last:	Flag set for the last message in the transfer
+ * @count:	Number of bytes to be sent/received in current transfer
+ * @pos:	Current position in the send/receive buffer
+ * @error:	Flag set when an error is received
+ * @lock:	To avoid race conditions between irq handler and xfer code
+ * @done:	Completion used to wait for transfer termination
+ * @frequency:	Operating frequency of I2C bus clock
+ * @tokens:	Sequence of tokens to be written to the device
+ * @num_tokens:	Number of tokens
+ */
+struct meson_i2c {
+	struct i2c_adapter	adap;
+	struct device		*dev;
+	void __iomem		*regs;
+	struct clk		*clk;
+	int			irq;
+
+	struct i2c_msg		*msg;
+	int			state;
+	bool			last;
+	int			count;
+	int			pos;
+	int			error;
+
+	spinlock_t		lock;
+	struct completion	done;
+	unsigned int		frequency;
+	u32			tokens[2];
+	int			num_tokens;
+};
+
+static void meson_i2c_set_mask(struct meson_i2c *i2c, int reg, u32 mask,
+			       u32 val)
+{
+	u32 data;
+
+	data = readl(i2c->regs + reg);
+	data &= ~mask;
+	data |= val & mask;
+	writel(data, i2c->regs + reg);
+}
+
+static void meson_i2c_reset_tokens(struct meson_i2c *i2c)
+{
+	i2c->tokens[0] = 0;
+	i2c->tokens[1] = 0;
+	i2c->num_tokens = 0;
+}
+
+static void meson_i2c_add_token(struct meson_i2c *i2c, int token)
+{
+	if (i2c->num_tokens < 8)
+		i2c->tokens[0] |= (token & 0xf) << (i2c->num_tokens * 4);
+	else
+		i2c->tokens[1] |= (token & 0xf) << ((i2c->num_tokens % 8) * 4);
+
+	i2c->num_tokens++;
+}
+
+static void meson_i2c_write_tokens(struct meson_i2c *i2c)
+{
+	writel(i2c->tokens[0], i2c->regs + REG_TOK_LIST0);
+	writel(i2c->tokens[1], i2c->regs + REG_TOK_LIST1);
+}
+
+static void meson_i2c_set_clk_div(struct meson_i2c *i2c)
+{
+	unsigned long clk_rate = clk_get_rate(i2c->clk);
+	unsigned int div;
+
+	div = DIV_ROUND_UP(clk_rate, i2c->frequency * 4);
+	meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_CLKDIV_MASK,
+			   div << REG_CTRL_CLKDIV_SHIFT);
+
+	dev_dbg(i2c->dev, "%s: clk %lu, freq %u, div %u\n", __func__,
+		clk_rate, i2c->frequency, div);
+}
+
+static void meson_i2c_get_data(struct meson_i2c *i2c, char *buf, int len)
+{
+	u32 rdata0, rdata1;
+	int i;
+
+	rdata0 = readl(i2c->regs + REG_TOK_RDATA0);
+	rdata1 = readl(i2c->regs + REG_TOK_RDATA1);
+
+	dev_dbg(i2c->dev, "%s: data %08x %08x len %d\n", __func__,
+		rdata0, rdata1, len);
+
+	for (i = 0; i < min_t(int, 4, len); i++)
+		*buf++ = (rdata0 >> i * 8) & 0xff;
+
+	for (i = 4; i < min_t(int, 8, len); i++)
+		*buf++ = (rdata1 >> (i - 4) * 8) & 0xff;
+}
+
+static void meson_i2c_put_data(struct meson_i2c *i2c, char *buf, int len)
+{
+	u32 wdata0 = 0, wdata1 = 0;
+	int i;
+
+	for (i = 0; i < min_t(int, 4, len); i++)
+		wdata0 |= *buf++ << (i * 8);
+
+	for (i = 4; i < min_t(int, 8, len); i++)
+		wdata1 |= *buf++ << ((i - 4) * 8);
+
+	writel(wdata0, i2c->regs + REG_TOK_WDATA0);
+	writel(wdata0, i2c->regs + REG_TOK_WDATA1);
+
+	dev_dbg(i2c->dev, "%s: data %08x %08x len %d\n", __func__,
+		wdata0, wdata1, len);
+}
+
+static void meson_i2c_prepare_xfer(struct meson_i2c *i2c)
+{
+	bool write = !(i2c->msg->flags & I2C_M_RD);
+	int i;
+
+	i2c->count = min_t(int, i2c->msg->len - i2c->pos, 8);
+
+	for (i = 0; i < i2c->count - 1; i++)
+		meson_i2c_add_token(i2c, TOKEN_DATA);
+
+	if (i2c->count) {
+		if (write || i2c->pos + i2c->count < i2c->msg->len)
+			meson_i2c_add_token(i2c, TOKEN_DATA);
+		else
+			meson_i2c_add_token(i2c, TOKEN_DATA_LAST);
+	}
+
+	if (write)
+		meson_i2c_put_data(i2c, i2c->msg->buf + i2c->pos, i2c->count);
+}
+
+static void meson_i2c_stop(struct meson_i2c *i2c)
+{
+	dev_dbg(i2c->dev, "%s: last %d\n", __func__, i2c->last);
+
+	if (i2c->last) {
+		i2c->state = STATE_STOP;
+		meson_i2c_add_token(i2c, TOKEN_STOP);
+	} else {
+		i2c->state = STATE_IDLE;
+		complete_all(&i2c->done);
+	}
+}
+
+static irqreturn_t meson_i2c_irq(int irqno, void *dev_id)
+{
+	struct meson_i2c *i2c = dev_id;
+	unsigned int ctrl;
+
+	spin_lock(&i2c->lock);
+
+	meson_i2c_reset_tokens(i2c);
+	ctrl = readl(i2c->regs + REG_CTRL);
+
+	dev_dbg(i2c->dev, "irq: state %d, pos %d, count %d, ctrl %08x\n",
+		i2c->state, i2c->pos, i2c->count, ctrl);
+
+	if (ctrl & REG_CTRL_ERROR && i2c->state != STATE_IDLE) {
+		/*
+		 * The bit is set when the IGNORE_NAK bit is cleared
+		 * and the device didn't respond. In this case, the
+		 * I2C controller automatically generates a STOP
+		 * condition.
+		 */
+		dev_dbg(i2c->dev, "error bit set\n");
+		i2c->error = -ENXIO;
+		i2c->state = STATE_IDLE;
+		complete_all(&i2c->done);
+		goto out;
+	}
+
+	switch (i2c->state) {
+	case STATE_READ:
+		if (i2c->count > 0) {
+			meson_i2c_get_data(i2c, i2c->msg->buf + i2c->pos,
+					   i2c->count);
+			i2c->pos += i2c->count;
+		}
+
+		if (i2c->pos >= i2c->msg->len) {
+			meson_i2c_stop(i2c);
+			break;
+		}
+
+		meson_i2c_prepare_xfer(i2c);
+		break;
+	case STATE_WRITE:
+		i2c->pos += i2c->count;
+
+		if (i2c->pos >= i2c->msg->len) {
+			meson_i2c_stop(i2c);
+			break;
+		}
+
+		meson_i2c_prepare_xfer(i2c);
+		break;
+	case STATE_STOP:
+		i2c->state = STATE_IDLE;
+		complete_all(&i2c->done);
+		break;
+	case STATE_IDLE:
+		break;
+	}
+
+out:
+	if (i2c->state != STATE_IDLE) {
+		/* Restart the processing */
+		meson_i2c_write_tokens(i2c);
+		meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, 0);
+		meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START,
+				   REG_CTRL_START);
+	}
+
+	spin_unlock(&i2c->lock);
+
+	return IRQ_HANDLED;
+}
+
+static void meson_i2c_do_start(struct meson_i2c *i2c, struct i2c_msg *msg)
+{
+	int token;
+
+	token = (msg->flags & I2C_M_RD) ? TOKEN_SLAVE_ADDR_READ :
+		TOKEN_SLAVE_ADDR_WRITE;
+
+	writel(msg->addr << 1, i2c->regs + REG_SLAVE_ADDR);
+	meson_i2c_add_token(i2c, TOKEN_START);
+	meson_i2c_add_token(i2c, token);
+}
+
+static int meson_i2c_xfer_msg(struct meson_i2c *i2c, struct i2c_msg *msg,
+			      int last)
+{
+	unsigned long time_left, flags;
+	int ret = 0;
+
+	i2c->msg = msg;
+	i2c->last = last;
+	i2c->pos = 0;
+	i2c->count = 0;
+	i2c->error = 0;
+
+	meson_i2c_reset_tokens(i2c);
+
+	flags = (msg->flags & I2C_M_IGNORE_NAK) ? REG_CTRL_ACK_IGNORE : 0;
+	meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_ACK_IGNORE, flags);
+
+	if (!(msg->flags & I2C_M_NOSTART))
+		meson_i2c_do_start(i2c, msg);
+
+	i2c->state = (msg->flags & I2C_M_RD) ? STATE_READ : STATE_WRITE;
+	meson_i2c_prepare_xfer(i2c);
+	meson_i2c_write_tokens(i2c);
+	reinit_completion(&i2c->done);
+
+	/* Start the transfer */
+	meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, REG_CTRL_START);
+
+	time_left = msecs_to_jiffies(I2C_TIMEOUT_MS);
+	time_left = wait_for_completion_timeout(&i2c->done, time_left);
+
+	/*
+	 * Protect access to i2c struct and registers from interrupt
+	 * handlers triggered by a transfer terminated after the
+	 * timeout period
+	 */
+	spin_lock_irqsave(&i2c->lock, flags);
+
+	/* Abort any active operation */
+	meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, 0);
+
+	if (!time_left) {
+		i2c->state = STATE_IDLE;
+		ret = -ETIMEDOUT;
+	}
+
+	if (i2c->error)
+		ret = i2c->error;
+
+	spin_unlock_irqrestore(&i2c->lock, flags);
+
+	return ret;
+}
+
+static int meson_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
+			  int num)
+{
+	struct meson_i2c *i2c = adap->algo_data;
+	int i, ret = 0, count = 0;
+
+	clk_enable(i2c->clk);
+	meson_i2c_set_clk_div(i2c);
+
+	for (i = 0; i < num; i++) {
+		ret = meson_i2c_xfer_msg(i2c, msgs + i, i == num - 1);
+		if (ret)
+			break;
+		count++;
+	}
+
+	clk_disable(i2c->clk);
+
+	return ret ? ret : count;
+}
+
+static u32 meson_i2c_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static const struct i2c_algorithm meson_i2c_algorithm = {
+	.master_xfer	= meson_i2c_xfer,
+	.functionality	= meson_i2c_func,
+};
+
+static int meson_i2c_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct meson_i2c *i2c;
+	struct resource *mem;
+	int ret = 0;
+
+	i2c = devm_kzalloc(&pdev->dev, sizeof(struct meson_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)) {
+		dev_err(&pdev->dev, "can't get device clock\n");
+		return PTR_ERR(i2c->clk);
+	}
+
+	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	i2c->regs = devm_ioremap_resource(&pdev->dev, mem);
+	if (IS_ERR(i2c->regs))
+		return PTR_ERR(i2c->regs);
+
+	i2c->irq = platform_get_irq(pdev, 0);
+	if (i2c->irq < 0) {
+		dev_err(&pdev->dev, "can't find IRQ\n");
+		return i2c->irq;
+	}
+
+	ret = devm_request_irq(&pdev->dev, i2c->irq, meson_i2c_irq,
+			       0, dev_name(&pdev->dev), i2c);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "can't request IRQ\n");
+		return ret;
+	}
+
+	ret = clk_prepare(i2c->clk);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "can't prepare clock\n");
+		return ret;
+	}
+
+	strlcpy(i2c->adap.name, "Meson I2C adapter",
+		sizeof(i2c->adap.name));
+	i2c->adap.owner = THIS_MODULE;
+	i2c->adap.algo = &meson_i2c_algorithm;
+	i2c->adap.dev.parent = &pdev->dev;
+	i2c->adap.dev.of_node = np;
+	i2c->adap.algo_data = i2c;
+
+	/*
+	 * A transfer is triggered when START bit changes from 0 to 1.
+	 * Ensure that the bit is set to 0 after probe
+	 */
+	meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_START, 0);
+
+	ret = i2c_add_adapter(&i2c->adap);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "can't register adapter\n");
+		clk_unprepare(i2c->clk);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int meson_i2c_remove(struct platform_device *pdev)
+{
+	struct meson_i2c *i2c = platform_get_drvdata(pdev);
+
+	i2c_del_adapter(&i2c->adap);
+	clk_unprepare(i2c->clk);
+
+	return 0;
+}
+
+static const struct of_device_id meson_i2c_match[] = {
+	{ .compatible = "amlogic,meson6-i2c" },
+	{ },
+};
+
+static struct platform_driver meson_i2c_driver = {
+	.probe   = meson_i2c_probe,
+	.remove  = meson_i2c_remove,
+	.driver  = {
+		.name  = "meson-i2c",
+		.of_match_table = meson_i2c_match,
+	},
+};
+
+module_platform_driver(meson_i2c_driver);
+
+MODULE_DESCRIPTION("Amlogic Meson I2C Bus driver");
+MODULE_AUTHOR("Beniamino Galvani <[e-mail]>");
+MODULE_LICENSE("GPL v2");