i2c: lpc2k: add driver

Add support for the I2C controller found on several NXP devices
including LPC2xxx, LPC178x/7x and LPC18xx/43xx. The controller
is implemented as a state machine and the driver act upon the
state changes when the bus is accessed.

The I2C controller supports master/slave operation, bus
arbitration, programmable clock rate, and speeds up to 1 Mbit/s.
Signed-off-by: Joachim Eastwood <manabian@gmail.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-lpc2k.txt

+NXP I2C controller for LPC2xxx/178x/18xx/43xx
+
+Required properties:
+ - compatible: must be "nxp,lpc1788-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:
+i2c0: i2c@400a1000 {
+	compatible = "nxp,lpc1788-i2c";
+	reg = <0x400a1000 0x1000>;
+	interrupts = <18>;
+	clocks = <&ccu1 CLK_APB1_I2C0>;
+	#address-cells = <1>;
+	#size-cells = <0>;
+};
+
+&i2c0 {
+	clock-frequency = <400000>;
+
+	lm75@48 {
+		compatible = "nxp,lm75";
+		reg = <0x48>;
+	};
+};
+

drivers/i2c/busses/Kconfig

@@ -619,6 +619,16 @@ config I2C_KEMPLD
 	  This driver can also be built as a module. If so, the module
 	  will be called i2c-kempld.
 
+config I2C_LPC2K
+	tristate "I2C bus support for NXP LPC2K/LPC178x/18xx/43xx"
+	depends on OF && (ARCH_LPC18XX || COMPILE_TEST)
+	help
+	  This driver supports the I2C interface found several NXP
+	  devices including LPC2xxx, LPC178x/7x and LPC18xx/43xx.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called i2c-lpc2k.
+
 config I2C_MESON
 	tristate "Amlogic Meson I2C controller"
 	depends on ARCH_MESON

drivers/i2c/busses/Makefile

@@ -59,6 +59,7 @@ obj-$(CONFIG_I2C_IMX)		+= i2c-imx.o
 obj-$(CONFIG_I2C_IOP3XX)	+= i2c-iop3xx.o
 obj-$(CONFIG_I2C_JZ4780)	+= i2c-jz4780.o
 obj-$(CONFIG_I2C_KEMPLD)	+= i2c-kempld.o
+obj-$(CONFIG_I2C_LPC2K)		+= i2c-lpc2k.o
 obj-$(CONFIG_I2C_MESON)		+= i2c-meson.o
 obj-$(CONFIG_I2C_MPC)		+= i2c-mpc.o
 obj-$(CONFIG_I2C_MT65XX)	+= i2c-mt65xx.o

drivers/i2c/busses/i2c-lpc2k.c

+/*
+ * Copyright (C) 2011 NXP Semiconductors
+ *
+ * Code portions referenced from the i2x-pxa and i2c-pnx drivers
+ *
+ * Make SMBus byte and word transactions work on LPC178x/7x
+ * Copyright (c) 2012
+ * Alexander Potashev, Emcraft Systems, aspotashev@emcraft.com
+ * Anton Protopopov, Emcraft Systems, antonp@emcraft.com
+ *
+ * Copyright (C) 2015 Joachim Eastwood <manabian@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ */
+
+#include <linux/clk.h>
+#include <linux/errno.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/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/sched.h>
+#include <linux/time.h>
+
+/* LPC24xx register offsets and bits */
+#define LPC24XX_I2CONSET	0x00
+#define LPC24XX_I2STAT		0x04
+#define LPC24XX_I2DAT		0x08
+#define LPC24XX_I2ADDR		0x0c
+#define LPC24XX_I2SCLH		0x10
+#define LPC24XX_I2SCLL		0x14
+#define LPC24XX_I2CONCLR	0x18
+
+#define LPC24XX_AA		BIT(2)
+#define LPC24XX_SI		BIT(3)
+#define LPC24XX_STO		BIT(4)
+#define LPC24XX_STA		BIT(5)
+#define LPC24XX_I2EN		BIT(6)
+
+#define LPC24XX_STO_AA		(LPC24XX_STO | LPC24XX_AA)
+#define LPC24XX_CLEAR_ALL	(LPC24XX_AA | LPC24XX_SI | LPC24XX_STO | \
+				 LPC24XX_STA | LPC24XX_I2EN)
+
+/* I2C SCL clock has different duty cycle depending on mode */
+#define I2C_STD_MODE_DUTY		46
+#define I2C_FAST_MODE_DUTY		36
+#define I2C_FAST_MODE_PLUS_DUTY		38
+
+/*
+ * 26 possible I2C status codes, but codes applicable only
+ * to master are listed here and used in this driver
+ */
+enum {
+	M_BUS_ERROR		= 0x00,
+	M_START			= 0x08,
+	M_REPSTART		= 0x10,
+	MX_ADDR_W_ACK		= 0x18,
+	MX_ADDR_W_NACK		= 0x20,
+	MX_DATA_W_ACK		= 0x28,
+	MX_DATA_W_NACK		= 0x30,
+	M_DATA_ARB_LOST		= 0x38,
+	MR_ADDR_R_ACK		= 0x40,
+	MR_ADDR_R_NACK		= 0x48,
+	MR_DATA_R_ACK		= 0x50,
+	MR_DATA_R_NACK		= 0x58,
+	M_I2C_IDLE		= 0xf8,
+};
+
+struct lpc2k_i2c {
+	void __iomem		*base;
+	struct clk		*clk;
+	int			irq;
+	wait_queue_head_t	wait;
+	struct i2c_adapter	adap;
+	struct i2c_msg		*msg;
+	int			msg_idx;
+	int			msg_status;
+	int			is_last;
+};
+
+static void i2c_lpc2k_reset(struct lpc2k_i2c *i2c)
+{
+	/* Will force clear all statuses */
+	writel(LPC24XX_CLEAR_ALL, i2c->base + LPC24XX_I2CONCLR);
+	writel(0, i2c->base + LPC24XX_I2ADDR);
+	writel(LPC24XX_I2EN, i2c->base + LPC24XX_I2CONSET);
+}
+
+static int i2c_lpc2k_clear_arb(struct lpc2k_i2c *i2c)
+{
+	unsigned long timeout = jiffies + msecs_to_jiffies(1000);
+
+	/*
+	 * If the transfer needs to abort for some reason, we'll try to
+	 * force a stop condition to clear any pending bus conditions
+	 */
+	writel(LPC24XX_STO, i2c->base + LPC24XX_I2CONSET);
+
+	/* Wait for status change */
+	while (readl(i2c->base + LPC24XX_I2STAT) != M_I2C_IDLE) {
+		if (time_after(jiffies, timeout)) {
+			/* Bus was not idle, try to reset adapter */
+			i2c_lpc2k_reset(i2c);
+			return -EBUSY;
+		}
+
+		cpu_relax();
+	}
+
+	return 0;
+}
+
+static void i2c_lpc2k_pump_msg(struct lpc2k_i2c *i2c)
+{
+	unsigned char data;
+	u32 status;
+
+	/*
+	 * I2C in the LPC2xxx series is basically a state machine.
+	 * Just run through the steps based on the current status.
+	 */
+	status = readl(i2c->base + LPC24XX_I2STAT);
+
+	switch (status) {
+	case M_START:
+	case M_REPSTART:
+		/* Start bit was just sent out, send out addr and dir */
+		data = i2c->msg->addr << 1;
+		if (i2c->msg->flags & I2C_M_RD)
+			data |= 1;
+
+		writel(data, i2c->base + LPC24XX_I2DAT);
+		writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONCLR);
+		break;
+
+	case MX_ADDR_W_ACK:
+	case MX_DATA_W_ACK:
+		/*
+		 * Address or data was sent out with an ACK. If there is more
+		 * data to send, send it now
+		 */
+		if (i2c->msg_idx < i2c->msg->len) {
+			writel(i2c->msg->buf[i2c->msg_idx],
+			       i2c->base + LPC24XX_I2DAT);
+		} else if (i2c->is_last) {
+			/* Last message, send stop */
+			writel(LPC24XX_STO_AA, i2c->base + LPC24XX_I2CONSET);
+			writel(LPC24XX_SI, i2c->base + LPC24XX_I2CONCLR);
+			i2c->msg_status = 0;
+			disable_irq_nosync(i2c->irq);
+		} else {
+			i2c->msg_status = 0;
+			disable_irq_nosync(i2c->irq);
+		}
+
+		i2c->msg_idx++;
+		break;
+
+	case MR_ADDR_R_ACK:
+		/* Receive first byte from slave */
+		if (i2c->msg->len == 1) {
+			/* Last byte, return NACK */
+			writel(LPC24XX_AA, i2c->base + LPC24XX_I2CONCLR);
+		} else {
+			/* Not last byte, return ACK */
+			writel(LPC24XX_AA, i2c->base + LPC24XX_I2CONSET);
+		}
+
+		writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONCLR);
+		break;
+
+	case MR_DATA_R_NACK:
+		/*
+		 * The I2C shows NACK status on reads, so we need to accept
+		 * the NACK as an ACK here. This should be ok, as the real
+		 * BACK would of been caught on the address write.
+		 */
+	case MR_DATA_R_ACK:
+		/* Data was received */
+		if (i2c->msg_idx < i2c->msg->len) {
+			i2c->msg->buf[i2c->msg_idx] =
+					readl(i2c->base + LPC24XX_I2DAT);
+		}
+
+		/* If transfer is done, send STOP */
+		if (i2c->msg_idx >= i2c->msg->len - 1 && i2c->is_last) {
+			writel(LPC24XX_STO_AA, i2c->base + LPC24XX_I2CONSET);
+			writel(LPC24XX_SI, i2c->base + LPC24XX_I2CONCLR);
+			i2c->msg_status = 0;
+		}
+
+		/* Message is done */
+		if (i2c->msg_idx >= i2c->msg->len - 1) {
+			i2c->msg_status = 0;
+			disable_irq_nosync(i2c->irq);
+		}
+
+		/*
+		 * One pre-last data input, send NACK to tell the slave that
+		 * this is going to be the last data byte to be transferred.
+		 */
+		if (i2c->msg_idx >= i2c->msg->len - 2) {
+			/* One byte left to receive - NACK */
+			writel(LPC24XX_AA, i2c->base + LPC24XX_I2CONCLR);
+		} else {
+			/* More than one byte left to receive - ACK */
+			writel(LPC24XX_AA, i2c->base + LPC24XX_I2CONSET);
+		}
+
+		writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONCLR);
+		i2c->msg_idx++;
+		break;
+
+	case MX_ADDR_W_NACK:
+	case MX_DATA_W_NACK:
+	case MR_ADDR_R_NACK:
+		/* NACK processing is done */
+		writel(LPC24XX_STO_AA, i2c->base + LPC24XX_I2CONSET);
+		i2c->msg_status = -ENXIO;
+		disable_irq_nosync(i2c->irq);
+		break;
+
+	case M_DATA_ARB_LOST:
+		/* Arbitration lost */
+		i2c->msg_status = -EAGAIN;
+
+		/* Release the I2C bus */
+		writel(LPC24XX_STA | LPC24XX_STO, i2c->base + LPC24XX_I2CONCLR);
+		disable_irq_nosync(i2c->irq);
+		break;
+
+	default:
+		/* Unexpected statuses */
+		i2c->msg_status = -EIO;
+		disable_irq_nosync(i2c->irq);
+		break;
+	}
+
+	/* Exit on failure or all bytes transferred */
+	if (i2c->msg_status != -EBUSY)
+		wake_up(&i2c->wait);
+
+	/*
+	 * If `msg_status` is zero, then `lpc2k_process_msg()`
+	 * is responsible for clearing the SI flag.
+	 */
+	if (i2c->msg_status != 0)
+		writel(LPC24XX_SI, i2c->base + LPC24XX_I2CONCLR);
+}
+
+static int lpc2k_process_msg(struct lpc2k_i2c *i2c, int msgidx)
+{
+	/* A new transfer is kicked off by initiating a start condition */
+	if (!msgidx) {
+		writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONSET);
+	} else {
+		/*
+		 * A multi-message I2C transfer continues where the
+		 * previous I2C transfer left off and uses the
+		 * current condition of the I2C adapter.
+		 */
+		if (unlikely(i2c->msg->flags & I2C_M_NOSTART)) {
+			WARN_ON(i2c->msg->len == 0);
+
+			if (!(i2c->msg->flags & I2C_M_RD)) {
+				/* Start transmit of data */
+				writel(i2c->msg->buf[0],
+				       i2c->base + LPC24XX_I2DAT);
+				i2c->msg_idx++;
+			}
+		} else {
+			/* Start or repeated start */
+			writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONSET);
+		}
+
+		writel(LPC24XX_SI, i2c->base + LPC24XX_I2CONCLR);
+	}
+
+	enable_irq(i2c->irq);
+
+	/* Wait for transfer completion */
+	if (wait_event_timeout(i2c->wait, i2c->msg_status != -EBUSY,
+			       msecs_to_jiffies(1000)) == 0) {
+		disable_irq_nosync(i2c->irq);
+
+		return -ETIMEDOUT;
+	}
+
+	return i2c->msg_status;
+}
+
+static int i2c_lpc2k_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
+			  int msg_num)
+{
+	struct lpc2k_i2c *i2c = i2c_get_adapdata(adap);
+	int ret, i;
+	u32 stat;
+
+	/* Check for bus idle condition */
+	stat = readl(i2c->base + LPC24XX_I2STAT);
+	if (stat != M_I2C_IDLE) {
+		/* Something is holding the bus, try to clear it */
+		return i2c_lpc2k_clear_arb(i2c);
+	}
+
+	/* Process a single message at a time */
+	for (i = 0; i < msg_num; i++) {
+		/* Save message pointer and current message data index */
+		i2c->msg = &msgs[i];
+		i2c->msg_idx = 0;
+		i2c->msg_status = -EBUSY;
+		i2c->is_last = (i == (msg_num - 1));
+
+		ret = lpc2k_process_msg(i2c, i);
+		if (ret)
+			return ret;
+	}
+
+	return msg_num;
+}
+
+static irqreturn_t i2c_lpc2k_handler(int irq, void *dev_id)
+{
+	struct lpc2k_i2c *i2c = dev_id;
+
+	if (readl(i2c->base + LPC24XX_I2CONSET) & LPC24XX_SI) {
+		i2c_lpc2k_pump_msg(i2c);
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
+static u32 i2c_lpc2k_functionality(struct i2c_adapter *adap)
+{
+	/* Only emulated SMBus for now */
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static const struct i2c_algorithm i2c_lpc2k_algorithm = {
+	.master_xfer	= i2c_lpc2k_xfer,
+	.functionality	= i2c_lpc2k_functionality,
+};
+
+static int i2c_lpc2k_probe(struct platform_device *pdev)
+{
+	struct lpc2k_i2c *i2c;
+	struct resource *res;
+	u32 bus_clk_rate;
+	u32 scl_high;
+	u32 clkrate;
+	int ret;
+
+	i2c = devm_kzalloc(&pdev->dev, sizeof(*i2c), GFP_KERNEL);
+	if (!i2c)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	i2c->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(i2c->base))
+		return PTR_ERR(i2c->base);
+
+	i2c->irq = platform_get_irq(pdev, 0);
+	if (i2c->irq < 0) {
+		dev_err(&pdev->dev, "can't get interrupt resource\n");
+		return i2c->irq;
+	}
+
+	init_waitqueue_head(&i2c->wait);
+
+	i2c->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(i2c->clk)) {
+		dev_err(&pdev->dev, "error getting clock\n");
+		return PTR_ERR(i2c->clk);
+	}
+
+	ret = clk_prepare_enable(i2c->clk);
+	if (ret) {
+		dev_err(&pdev->dev, "unable to enable clock.\n");
+		return ret;
+	}
+
+	ret = devm_request_irq(&pdev->dev, i2c->irq, i2c_lpc2k_handler, 0,
+			       dev_name(&pdev->dev), i2c);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "can't request interrupt.\n");
+		goto fail_clk;
+	}
+
+	disable_irq_nosync(i2c->irq);
+
+	/* Place controller is a known state */
+	i2c_lpc2k_reset(i2c);
+
+	ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
+				   &bus_clk_rate);
+	if (ret)
+		bus_clk_rate = 100000; /* 100 kHz default clock rate */
+
+	clkrate = clk_get_rate(i2c->clk);
+	if (clkrate == 0) {
+		dev_err(&pdev->dev, "can't get I2C base clock\n");
+		ret = -EINVAL;
+		goto fail_clk;
+	}
+
+	/* Setup I2C dividers to generate clock with proper duty cycle */
+	clkrate = clkrate / bus_clk_rate;
+	if (bus_clk_rate <= 100000)
+		scl_high = (clkrate * I2C_STD_MODE_DUTY) / 100;
+	else if (bus_clk_rate <= 400000)
+		scl_high = (clkrate * I2C_FAST_MODE_DUTY) / 100;
+	else
+		scl_high = (clkrate * I2C_FAST_MODE_PLUS_DUTY) / 100;
+
+	writel(scl_high, i2c->base + LPC24XX_I2SCLH);
+	writel(clkrate - scl_high, i2c->base + LPC24XX_I2SCLL);
+
+	platform_set_drvdata(pdev, i2c);
+
+	i2c_set_adapdata(&i2c->adap, i2c);
+	i2c->adap.owner = THIS_MODULE;
+	strlcpy(i2c->adap.name, "LPC2K I2C adapter", sizeof(i2c->adap.name));
+	i2c->adap.algo = &i2c_lpc2k_algorithm;
+	i2c->adap.dev.parent = &pdev->dev;
+	i2c->adap.dev.of_node = pdev->dev.of_node;
+
+	ret = i2c_add_adapter(&i2c->adap);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "failed to add adapter!\n");
+		goto fail_clk;
+	}
+
+	dev_info(&pdev->dev, "LPC2K I2C adapter\n");
+
+	return 0;
+
+fail_clk:
+	clk_disable_unprepare(i2c->clk);
+	return ret;
+}
+
+static int i2c_lpc2k_remove(struct platform_device *dev)
+{
+	struct lpc2k_i2c *i2c = platform_get_drvdata(dev);
+
+	i2c_del_adapter(&i2c->adap);
+	clk_disable_unprepare(i2c->clk);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int i2c_lpc2k_suspend(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct lpc2k_i2c *i2c = platform_get_drvdata(pdev);
+
+	clk_disable(i2c->clk);
+
+	return 0;
+}
+
+static int i2c_lpc2k_resume(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct lpc2k_i2c *i2c = platform_get_drvdata(pdev);
+
+	clk_enable(i2c->clk);
+	i2c_lpc2k_reset(i2c);
+
+	return 0;
+}
+
+static const struct dev_pm_ops i2c_lpc2k_dev_pm_ops = {
+	.suspend_noirq = i2c_lpc2k_suspend,
+	.resume_noirq = i2c_lpc2k_resume,
+};
+
+#define I2C_LPC2K_DEV_PM_OPS (&i2c_lpc2k_dev_pm_ops)
+#else
+#define I2C_LPC2K_DEV_PM_OPS NULL
+#endif
+
+static const struct of_device_id lpc2k_i2c_match[] = {
+	{ .compatible = "nxp,lpc1788-i2c" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, lpc2k_i2c_match);
+
+static struct platform_driver i2c_lpc2k_driver = {
+	.probe	= i2c_lpc2k_probe,
+	.remove	= i2c_lpc2k_remove,
+	.driver	= {
+		.name		= "lpc2k-i2c",
+		.pm		= I2C_LPC2K_DEV_PM_OPS,
+		.of_match_table	= lpc2k_i2c_match,
+	},
+};
+module_platform_driver(i2c_lpc2k_driver);
+
+MODULE_AUTHOR("Kevin Wells <kevin.wells@nxp.com>");
+MODULE_DESCRIPTION("I2C driver for LPC2xxx devices");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:lpc2k-i2c");