Add I2C support for Allwinner SoCs

This patch implements a basic driver for the I2C host driver found on the Allwinner A10, A13 and A31 SoCs.

Notable missing feature is 10-bit addressing.

Signed-off-by Maxime Ripard <[email protected]>

---
 .../devicetree/bindings/i2c/i2c-sunxi.txt          |  19 +
 drivers/i2c/busses/Kconfig                         |  10 +
 drivers/i2c/busses/Makefile                        |   1 +
 drivers/i2c/busses/i2c-sunxi.c                     | 441
+++++++++++++++++++++ 4 files changed, 471 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/i2c/i2c-sunxi.txt
 create mode 100644 drivers/i2c/busses/i2c-sunxi.c

(quoted diff) +0 -0

b/Documentation/devicetree/bindings/i2c/i2c-sunxi.txt new file mode 100644
index 0000000..40c16d0

Documentation/devicetree/bindings/i2c/i2c-sunxi.txt new file +19 -0

@@ -0,0 +1,19 @@
+Allwinner SoC I2C controller
+
+Required properties:
+- compatible : Should be "allwinner,sun4i-i2c".
+- reg: Should contain register location and length.
+- interrupts: Should contain interrupt.
+- clocks : The parent clock feeding the I2C controller.
+
+Recommended properties:
+- clock-frequency : desired I2C bus clock frequency in Hz.
+
+Example:
+i2c0: i2c at 01c2ac00 {
+	compatible = "allwinner,sun4i-i2c";
+	reg = <0x01c2ac00 0x400>;
+	interrupts = <7>;
+	clocks = <&apb1_gates 0>;
+	clock-frequency = <100000>;
+};

drivers/i2c/busses/Kconfig +10 -0

index adfee98..327a49b 100644
@@ -706,6 +706,16 @@ config I2C_STU300
 	  This driver can also be built as a module. If so, the module
 	  will be called i2c-stu300.
 
+config I2C_SUNXI
+	tristate "Allwinner A1X I2C controller"
+	depends on ARCH_SUNXI
+	help
+	  If you say yes to this option, support will be included for the
+	  I2C controller embedded in Allwinner A1X SoCs.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called i2c-sunxi.
+
 config I2C_TEGRA
 	tristate "NVIDIA Tegra internal I2C controller"
 	depends on ARCH_TEGRA

drivers/i2c/busses/Makefile +1 -0

index 8f4fc23..7225818 100644
@@ -69,6 +69,7 @@ obj-$(CONFIG_I2C_SH_MOBILE)	+= i2c-sh_mobile.o
 obj-$(CONFIG_I2C_SIMTEC)	+= i2c-simtec.o
 obj-$(CONFIG_I2C_SIRF)		+= i2c-sirf.o
 obj-$(CONFIG_I2C_STU300)	+= i2c-stu300.o
+obj-$(CONFIG_I2C_SUNXI)		+= i2c-sunxi.o
 obj-$(CONFIG_I2C_TEGRA)		+= i2c-tegra.o
 obj-$(CONFIG_I2C_VERSATILE)	+= i2c-versatile.o
 obj-$(CONFIG_I2C_OCTEON)	+= i2c-octeon.o

(quoted diff) +0 -0

b/drivers/i2c/busses/i2c-sunxi.c new file mode 100644 index 0000000..f9f8bd4

drivers/i2c/busses/i2c-sunxi.c new file +74 -0

@@ -0,0 +1,441 @@
+/*
+ * Allwinner A1X SoCs i2c controller driver.
+ *
+ * Copyright (C) 2013 Maxime Ripard
+ *
+ * Maxime Ripard <[email protected]>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2.  This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/clk.h>
+#include <linux/completion.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+
+#define SUNXI_I2C_ADDR_REG		(0x00)
+#define SUNXI_I2C_ADDR_ADDR(v)			((v & 0x7f) << 1)
+#define SUNXI_I2C_XADDR_REG		(0x04)
+#define SUNXI_I2C_DATA_REG		(0x08)
+#define SUNXI_I2C_CNTR_REG		(0x0c)
+#define SUNXI_I2C_CNTR_ASSERT_ACK		BIT(2)
+#define SUNXI_I2C_CNTR_INT_FLAG			BIT(3)
+#define SUNXI_I2C_CNTR_MASTER_STOP		BIT(4)
+#define SUNXI_I2C_CNTR_MASTER_START		BIT(5)
+#define SUNXI_I2C_CNTR_BUS_ENABLE		BIT(6)
+#define SUNXI_I2C_CNTR_INT_ENABLE		BIT(7)
+#define SUNXI_I2C_STA_REG		(0x10)
+#define SUNXI_I2C_STA_BUS_ERROR			(0x00)
+#define SUNXI_I2C_STA_START			(0x08)
+#define SUNXI_I2C_STA_START_REPEAT		(0x10)
+#define SUNXI_I2C_STA_MASTER_WADDR_ACK		(0x18)
+#define SUNXI_I2C_STA_MASTER_WADDR_NAK		(0x20)
+#define SUNXI_I2C_STA_MASTER_DATA_SENT_ACK	(0x28)
+#define SUNXI_I2C_STA_MASTER_DATA_SENT_NAK	(0x30)
+#define SUNXI_I2C_STA_MASTER_RADDR_ACK		(0x40)
+#define SUNXI_I2C_STA_MASTER_RADDR_NAK		(0x48)
+#define SUNXI_I2C_STA_MASTER_DATA_RECV_ACK	(0x50)
+#define SUNXI_I2C_STA_MASTER_DATA_RECV_NAK	(0x58)
+#define SUNXI_I2C_CCR_REG		(0x14)
+#define SUNXI_I2C_CCR_DIV_N(val)		(val & 0x3)
+#define SUNXI_I2C_CCR_DIV_M(val)		((val & 0xf) << 3)
+#define SUNXI_I2C_SRST_REG		(0x18)
+#define SUNXI_I2C_SRST_RESET			BIT(0)
+#define SUNXI_I2C_EFR_REG		(0x1c)
+#define SUNXI_I2C_LCR_REG		(0x20)
+
+#define SUNXI_I2C_DONE			BIT(0)
+#define SUNXI_I2C_ERROR			BIT(1)
+#define SUNXI_I2C_NAK			BIT(2)
+#define SUNXI_I2C_BUS_ERROR		BIT(3)
+
+struct sunxi_i2c_dev {
+	struct i2c_adapter	adapter;
+	struct clk		*clk;
+	struct device		*dev;
+	struct completion	completion;
+	unsigned int		irq;
+	void __iomem		*membase;
+
+	struct i2c_msg		*msg_cur;
+	u8			*msg_buf;
+	size_t			msg_buf_remaining;
+	unsigned int		msg_err;
+};
+
+static void sunxi_i2c_write(struct sunxi_i2c_dev *i2c_dev, u16 reg, u8

value) +{

drivers/i2c/busses/i2c-sunxi.c new file +45 -0

+	writel(value, i2c_dev->membase + reg);
+}
+
+static u32 sunxi_i2c_read(struct sunxi_i2c_dev *i2c_dev, u16 reg)
+{
+	return readl(i2c_dev->membase + reg);
+}
+
+/*
+ * This is where all the magic happens. The I2C controller works as a
+ * state machine, each state being a step in the i2c protocol, with
+ * the controller sending an interrupt at each state transition.
+ *
+ * The state we're in is stored in a register, which leads to a pretty
+ * huge switch statement, all of this in the interrupt handler...
+ */
+static irqreturn_t sunxi_i2c_handler(int irq, void *data)
+{
+	struct sunxi_i2c_dev *i2c_dev = (struct sunxi_i2c_dev *)data;
+	u32 status = sunxi_i2c_read(i2c_dev, SUNXI_I2C_CNTR_REG);
+	u32 addr, val;
+
+	if (!(status & SUNXI_I2C_CNTR_INT_FLAG))
+		return IRQ_NONE;
+
+	/* Read the current state we're in */
+	status = sunxi_i2c_read(i2c_dev, SUNXI_I2C_STA_REG);
+
+	switch (status & 0xff) {
+	/* Start condition has been transmitted */
+	case SUNXI_I2C_STA_START:
+	/* A repeated start condition has been transmitted */
+	case SUNXI_I2C_STA_START_REPEAT:
+		addr = SUNXI_I2C_ADDR_ADDR(i2c_dev->msg_cur->addr);
+
+		if (i2c_dev->msg_cur->flags & I2C_M_RD)
+			addr |= 1;
+
+		sunxi_i2c_write(i2c_dev, SUNXI_I2C_DATA_REG, addr);
+		break;
+
+	/*
+	 * Address + Write bit have been transmitted, ACK has not been
+	 * received.
+	 */

drivers/i2c/busses/i2c-sunxi.c new file +22 -0

+
+	/*
+	 * Address + Write bit have been transmitted, ACK has been
+	 * received
+	 */
+	case SUNXI_I2C_STA_MASTER_WADDR_ACK:
+	/* Data byte has been transmitted, ACK has been received */
+	case SUNXI_I2C_STA_MASTER_DATA_SENT_ACK:
+		if (i2c_dev->msg_buf_remaining) {
+			sunxi_i2c_write(i2c_dev, SUNXI_I2C_DATA_REG,
+					*i2c_dev->msg_buf);
+			i2c_dev->msg_buf++;
+			i2c_dev->msg_buf_remaining--;
+			break;
+		}
+
+		if (i2c_dev->msg_buf_remaining == 0) {
+			i2c_dev->msg_err = SUNXI_I2C_DONE;
+			goto out;
+		}
+
+		break;

drivers/i2c/busses/i2c-sunxi.c new file +25 -0

+
+	/*
+	 * Address + Read bit have been transmitted, ACK has been
+	 * received
+	 */
+	case SUNXI_I2C_STA_MASTER_RADDR_ACK:
+		/*
+		 * We only need to send the ACK for the all the bytes
+		 * but the last one
+		 */
+		if (i2c_dev->msg_buf_remaining > 1) {
+			val = sunxi_i2c_read(i2c_dev, SUNXI_I2C_CNTR_REG);
+			sunxi_i2c_write(i2c_dev, SUNXI_I2C_CNTR_REG,
+					val | SUNXI_I2C_CNTR_ASSERT_ACK);
+		}
+
+		break;
+
+	/*
+	 * Data byte has been received, ACK has not been
+	 * transmitted
+	 */
+	case SUNXI_I2C_STA_MASTER_DATA_RECV_NAK:
+		if (i2c_dev->msg_buf_remaining == 1) {
+			val = sunxi_i2c_read(i2c_dev, SUNXI_I2C_DATA_REG);

drivers/i2c/busses/i2c-sunxi.c new file +73 -0

+
+	/* Data byte has been received, ACK has been transmitted */
+	case SUNXI_I2C_STA_MASTER_DATA_RECV_ACK:
+		val = sunxi_i2c_read(i2c_dev, SUNXI_I2C_DATA_REG) & 0xff;
+		*i2c_dev->msg_buf = val;
+		i2c_dev->msg_buf++;
+		i2c_dev->msg_buf_remaining--;
+
+		/* If there's only one byte left, disable the ACK */
+		if (i2c_dev->msg_buf_remaining == 1) {
+			val = sunxi_i2c_read(i2c_dev, SUNXI_I2C_CNTR_REG);
+			sunxi_i2c_write(i2c_dev, SUNXI_I2C_CNTR_REG,
+					val & ~SUNXI_I2C_CNTR_ASSERT_ACK);
+
+		};
+
+		break;
+
+	case SUNXI_I2C_STA_BUS_ERROR:
+		i2c_dev->msg_err = SUNXI_I2C_BUS_ERROR;
+		goto out;
+
+	default:
+		i2c_dev->msg_err = SUNXI_I2C_ERROR;
+		goto out;
+	}
+
+	val = sunxi_i2c_read(i2c_dev, SUNXI_I2C_CNTR_REG);
+	sunxi_i2c_write(i2c_dev, SUNXI_I2C_CNTR_REG,
+			val & ~SUNXI_I2C_CNTR_INT_FLAG);
+
+	return IRQ_HANDLED;
+
+out:
+	val = sunxi_i2c_read(i2c_dev, SUNXI_I2C_CNTR_REG);
+	sunxi_i2c_write(i2c_dev, SUNXI_I2C_CNTR_REG,
+			val | SUNXI_I2C_CNTR_MASTER_STOP);
+
+	val = sunxi_i2c_read(i2c_dev, SUNXI_I2C_CNTR_REG);
+	sunxi_i2c_write(i2c_dev, SUNXI_I2C_CNTR_REG,
+			val & ~SUNXI_I2C_CNTR_INT_FLAG);
+
+	complete(&i2c_dev->completion);
+	return IRQ_HANDLED;
+}
+
+static int sunxi_i2c_xfer_msg(struct sunxi_i2c_dev *i2c_dev,
+			      struct i2c_msg *msg)
+{
+	int time_left;
+	u32 val;
+
+	i2c_dev->msg_cur = msg;
+	i2c_dev->msg_buf = msg->buf;
+	i2c_dev->msg_buf_remaining = msg->len;
+	i2c_dev->msg_err = 0;
+	INIT_COMPLETION(i2c_dev->completion);
+
+	val = sunxi_i2c_read(i2c_dev, SUNXI_I2C_CNTR_REG);
+	val |= SUNXI_I2C_CNTR_MASTER_START;
+	sunxi_i2c_write(i2c_dev, SUNXI_I2C_CNTR_REG, val);
+
+	time_left = wait_for_completion_timeout(&i2c_dev->completion,
+						i2c_dev->adapter.timeout);
+	if (!time_left) {
+		dev_err(i2c_dev->dev, "i2c transfer timed out\n");
+		return -ETIMEDOUT;
+	}
+
+	if (likely(i2c_dev->msg_err == SUNXI_I2C_DONE))
+		return 0;
+
+	dev_dbg(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev-

msg_err);

drivers/i2c/busses/i2c-sunxi.c new file +5 -0

+
+	return -EIO;
+}
+
+static int sunxi_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg

*msgs, + int num)

drivers/i2c/busses/i2c-sunxi.c new file +33 -0

+{
+	struct sunxi_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
+	int i, ret;
+
+	for (i = 0; i < num; i++) {
+		ret = sunxi_i2c_xfer_msg(i2c_dev, &msgs[i]);
+		if (ret)
+			return ret;
+	}
+
+	return i;
+}
+
+static u32 sunxi_i2c_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static const struct i2c_algorithm sunxi_i2c_algo = {
+	.master_xfer	= sunxi_i2c_xfer,
+	.functionality	= sunxi_i2c_func,
+};
+
+static int sunxi_i2c_probe(struct platform_device *pdev)
+{
+	struct sunxi_i2c_dev *i2c_dev;
+	struct device_node *np;
+	u32 freq, div_m, div_n;
+	int ret;
+
+	np = pdev->dev.of_node;
+	if (!np)
+		return -EINVAL;

drivers/i2c/busses/i2c-sunxi.c new file +24 -0

+		freq = 100000;
+	}
+
+	/*
+	 * Set the clock dividers. we don't need to be super smart
+	 * here, the datasheet defines the value of the factors for
+	 * the two supported frequencies, and only the M factor
+	 * changes between 100kHz and 400kHz.
+	 *
+	 * The bus clock is generated from the parent clock with two
+	 * different dividers. It is generated as such:
+	 *     f0 = fclk / (2 ^ DIV_N)
+	 *     fbus = f0 / (10 * (DIV_M + 1))
+	 *
+	 * With DIV_N being on 3 bits, and DIV_M on 4 bits.
+	 * So DIV_N < 8, and DIV_M < 16.
+	 *
+	 * However, we can generate both the supported frequencies
+	 * with f0 = 12MHz, and only change M to get back on our
+	 * feet.
+	 */
+	div_n = ilog2(clk_get_rate(i2c_dev->clk) / 12000000);
+	if (freq == 100000)
+		div_m = 11;

drivers/i2c/busses/i2c-sunxi.c new file +5 -0

+	if (ret) {
+		dev_err(&pdev->dev, "Could not request IRQ\n");
+		goto out_clk_dis;
+	}
+

drivers/i2c/busses/i2c-sunxi.c new file +48 -0

+
+	ret = i2c_add_adapter(&i2c_dev->adapter);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to register i2c adapter\n");
+		goto out_clk_dis;
+	}
+
+	return 0;
+
+out_clk_dis:
+	clk_disable_unprepare(i2c_dev->clk);
+out_iounmap:
+	iounmap(i2c_dev->membase);
+	return ret;
+}
+
+
+static int sunxi_i2c_remove(struct platform_device *pdev)
+{
+	struct sunxi_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
+
+	i2c_del_adapter(&i2c_dev->adapter);
+	clk_disable_unprepare(i2c_dev->clk);
+	iounmap(i2c_dev->membase);
+
+	return 0;
+}
+
+static const struct of_device_id sunxi_i2c_of_match[] = {
+	{ .compatible = "allwinner,sun4i-i2c" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, sunxi_i2c_of_match);
+
+static struct platform_driver sunxi_i2c_driver = {
+	.probe		= sunxi_i2c_probe,
+	.remove		= sunxi_i2c_remove,
+	.driver		= {
+		.name	= "i2c-sunxi",
+		.owner	= THIS_MODULE,
+		.of_match_table = sunxi_i2c_of_match,
+	},
+};
+module_platform_driver(sunxi_i2c_driver);
+
+MODULE_AUTHOR("Maxime Ripard <[email protected]");
+MODULE_DESCRIPTION("Allwinner A1X I2C bus adapter");
+MODULE_LICENSE("GPL");

Hi Maxime,

Overall the driver looks good, just some minor nitpicks inline.

Hi,

This patchset adds support for the I2C controller found on most of the Allwinner SoCs, especially the already supported A10 and A13, and the yet to come A31.

It has been tested on a A13-Olinuxino.

Thanks,
Maxime

Resent to fix Wolfram's email address.