i2c: emev2: add driver

Add a basic driver for the Renesas EMEV2 SoC. Based on the driver from
the BSP which was first worked on by Ian, and made ready for upstream by
me.
Signed-off-by: Ian Molton <ian.molton@codethink.co.uk>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-emev2.txt

+Device tree configuration for Renesas EMEV2 IIC controller
+
+Required properties:
+- compatible      : "renesas,iic-emev2"
+- reg             : address start and address range size of device
+- interrupts      : specifier for the IIC controller interrupt
+- clocks          : phandle to the IP core SCLK
+- clock-names     : must be "sclk"
+- #address-cells  : should be <1>
+- #size-cells     : should be <0>
+
+Example:
+
+	iic0: i2c@e0070000 {
+		#address-cells = <1>;
+		#size-cells = <0>;
+		compatible = "renesas,iic-emev2";
+		reg = <0xe0070000 0x28>;
+		interrupts = <0 32 IRQ_TYPE_EDGE_RISING>;
+		clocks = <&iic0_sclk>;
+		clock-names = "sclk";
+	};

drivers/i2c/busses/Kconfig

@@ -526,6 +526,13 @@ config I2C_EG20T
 	  ML7213/ML7223/ML7831 is companion chip for Intel Atom E6xx series.
 	  ML7213/ML7223/ML7831 is completely compatible for Intel EG20T PCH.
 
+config I2C_EMEV2
+	tristate "EMMA Mobile series I2C adapter"
+	depends on HAVE_CLK
+	help
+	  If you say yes to this option, support will be included for the
+	  I2C interface on the Renesas Electronics EM/EV family of processors.
+
 config I2C_EXYNOS5
 	tristate "Exynos5 high-speed I2C driver"
 	depends on ARCH_EXYNOS && OF

drivers/i2c/busses/Makefile

@@ -48,6 +48,7 @@ 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_EMEV2)		+= i2c-emev2.o
 obj-$(CONFIG_I2C_EXYNOS5)	+= i2c-exynos5.o
 obj-$(CONFIG_I2C_GPIO)		+= i2c-gpio.o
 obj-$(CONFIG_I2C_HIGHLANDER)	+= i2c-highlander.o

drivers/i2c/busses/i2c-emev2.c

+/*
+ * I2C driver for the Renesas EMEV2 SoC
+ *
+ * Copyright (C) 2015 Wolfram Sang <wsa@sang-engineering.com>
+ * Copyright 2013 Codethink Ltd.
+ * Copyright 2010-2015 Renesas Electronics Corporation
+ *
+ * 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/device.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/sched.h>
+
+/* I2C Registers */
+#define I2C_OFS_IICACT0		0x00	/* start */
+#define I2C_OFS_IIC0		0x04	/* shift */
+#define I2C_OFS_IICC0		0x08	/* control */
+#define I2C_OFS_SVA0		0x0c	/* slave address */
+#define I2C_OFS_IICCL0		0x10	/* clock select */
+#define I2C_OFS_IICX0		0x14	/* extension */
+#define I2C_OFS_IICS0		0x18	/* status */
+#define I2C_OFS_IICSE0		0x1c	/* status For emulation */
+#define I2C_OFS_IICF0		0x20	/* IIC flag */
+
+/* I2C IICACT0 Masks */
+#define I2C_BIT_IICE0		0x0001
+
+/* I2C IICC0 Masks */
+#define I2C_BIT_LREL0		0x0040
+#define I2C_BIT_WREL0		0x0020
+#define I2C_BIT_SPIE0		0x0010
+#define I2C_BIT_WTIM0		0x0008
+#define I2C_BIT_ACKE0		0x0004
+#define I2C_BIT_STT0		0x0002
+#define I2C_BIT_SPT0		0x0001
+
+/* I2C IICCL0 Masks */
+#define I2C_BIT_SMC0		0x0008
+#define I2C_BIT_DFC0		0x0004
+
+/* I2C IICSE0 Masks */
+#define I2C_BIT_MSTS0		0x0080
+#define I2C_BIT_ALD0		0x0040
+#define I2C_BIT_EXC0		0x0020
+#define I2C_BIT_COI0		0x0010
+#define I2C_BIT_TRC0		0x0008
+#define I2C_BIT_ACKD0		0x0004
+#define I2C_BIT_STD0		0x0002
+#define I2C_BIT_SPD0		0x0001
+
+/* I2C IICF0 Masks */
+#define I2C_BIT_STCF		0x0080
+#define I2C_BIT_IICBSY		0x0040
+#define I2C_BIT_STCEN		0x0002
+#define I2C_BIT_IICRSV		0x0001
+
+struct em_i2c_device {
+	void __iomem *base;
+	struct i2c_adapter adap;
+	struct completion msg_done;
+	struct clk *sclk;
+};
+
+static inline void em_clear_set_bit(struct em_i2c_device *priv, u8 clear, u8 set, u8 reg)
+{
+	writeb((readb(priv->base + reg) & ~clear) | set, priv->base + reg);
+}
+
+static int em_i2c_wait_for_event(struct em_i2c_device *priv)
+{
+	unsigned long time_left;
+	int status;
+
+	reinit_completion(&priv->msg_done);
+
+	time_left = wait_for_completion_timeout(&priv->msg_done, priv->adap.timeout);
+
+	if (!time_left)
+		return -ETIMEDOUT;
+
+	status = readb(priv->base + I2C_OFS_IICSE0);
+	return status & I2C_BIT_ALD0 ? -EAGAIN : status;
+}
+
+static void em_i2c_stop(struct em_i2c_device *priv)
+{
+	/* Send Stop condition */
+	em_clear_set_bit(priv, 0, I2C_BIT_SPT0 | I2C_BIT_SPIE0, I2C_OFS_IICC0);
+
+	/* Wait for stop condition */
+	em_i2c_wait_for_event(priv);
+}
+
+static void em_i2c_reset(struct i2c_adapter *adap)
+{
+	struct em_i2c_device *priv = i2c_get_adapdata(adap);
+	int retr;
+
+	/* If I2C active */
+	if (readb(priv->base + I2C_OFS_IICACT0) & I2C_BIT_IICE0) {
+		/* Disable I2C operation */
+		writeb(0, priv->base + I2C_OFS_IICACT0);
+
+		retr = 1000;
+		while (readb(priv->base + I2C_OFS_IICACT0) == 1 && retr)
+			retr--;
+		WARN_ON(retr == 0);
+	}
+
+	/* Transfer mode set */
+	writeb(I2C_BIT_DFC0, priv->base + I2C_OFS_IICCL0);
+
+	/* Can Issue start without detecting a stop, Reservation disabled. */
+	writeb(I2C_BIT_STCEN | I2C_BIT_IICRSV, priv->base + I2C_OFS_IICF0);
+
+	/* I2C enable, 9 bit interrupt mode */
+	writeb(I2C_BIT_WTIM0, priv->base + I2C_OFS_IICC0);
+
+	/* Enable I2C operation */
+	writeb(I2C_BIT_IICE0, priv->base + I2C_OFS_IICACT0);
+
+	retr = 1000;
+	while (readb(priv->base + I2C_OFS_IICACT0) == 0 && retr)
+		retr--;
+	WARN_ON(retr == 0);
+}
+
+static int __em_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msg,
+				int stop)
+{
+	struct em_i2c_device *priv = i2c_get_adapdata(adap);
+	int count, status, read = !!(msg->flags & I2C_M_RD);
+
+	/* Send start condition */
+	em_clear_set_bit(priv, 0, I2C_BIT_ACKE0 | I2C_BIT_WTIM0, I2C_OFS_IICC0);
+	em_clear_set_bit(priv, 0, I2C_BIT_STT0, I2C_OFS_IICC0);
+
+	/* Send slave address and R/W type */
+	writeb((msg->addr << 1) | read, priv->base + I2C_OFS_IIC0);
+
+	/* Wait for transaction */
+	status = em_i2c_wait_for_event(priv);
+	if (status < 0)
+		goto out_reset;
+
+	/* Received NACK (result of setting slave address and R/W) */
+	if (!(status & I2C_BIT_ACKD0)) {
+		em_i2c_stop(priv);
+		goto out;
+	}
+
+	/* Extra setup for read transactions */
+	if (read) {
+		/* 8 bit interrupt mode */
+		em_clear_set_bit(priv, I2C_BIT_WTIM0, I2C_BIT_ACKE0, I2C_OFS_IICC0);
+		em_clear_set_bit(priv, I2C_BIT_WTIM0, I2C_BIT_WREL0, I2C_OFS_IICC0);
+
+		/* Wait for transaction */
+		status = em_i2c_wait_for_event(priv);
+		if (status < 0)
+			goto out_reset;
+	}
+
+	/* Send / receive data */
+	for (count = 0; count < msg->len; count++) {
+		if (read) { /* Read transaction */
+			msg->buf[count] = readb(priv->base + I2C_OFS_IIC0);
+			em_clear_set_bit(priv, 0, I2C_BIT_WREL0, I2C_OFS_IICC0);
+
+		} else { /* Write transaction */
+			/* Received NACK */
+			if (!(status & I2C_BIT_ACKD0)) {
+				em_i2c_stop(priv);
+				goto out;
+			}
+
+			/* Write data */
+			writeb(msg->buf[count], priv->base + I2C_OFS_IIC0);
+		}
+
+		/* Wait for R/W transaction */
+		status = em_i2c_wait_for_event(priv);
+		if (status < 0)
+			goto out_reset;
+	}
+
+	if (stop)
+		em_i2c_stop(priv);
+
+	return count;
+
+out_reset:
+	em_i2c_reset(adap);
+out:
+	return status < 0 ? status : -ENXIO;
+}
+
+static int em_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
+	int num)
+{
+	struct em_i2c_device *priv = i2c_get_adapdata(adap);
+	int ret, i;
+
+	if (readb(priv->base + I2C_OFS_IICF0) & I2C_BIT_IICBSY)
+		return -EAGAIN;
+
+	for (i = 0; i < num; i++) {
+		ret = __em_i2c_xfer(adap, &msgs[i], (i == (num - 1)));
+		if (ret < 0)
+			return ret;
+	}
+
+	/* I2C transfer completed */
+	return num;
+}
+
+static irqreturn_t em_i2c_irq_handler(int this_irq, void *dev_id)
+{
+	struct em_i2c_device *priv = dev_id;
+
+	complete(&priv->msg_done);
+	return IRQ_HANDLED;
+}
+
+static u32 em_i2c_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static struct i2c_algorithm em_i2c_algo = {
+	.master_xfer = em_i2c_xfer,
+	.functionality = em_i2c_func,
+};
+
+static int em_i2c_probe(struct platform_device *pdev)
+{
+	struct em_i2c_device *priv;
+	struct resource *r;
+	int irq, ret;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	priv->base = devm_ioremap_resource(&pdev->dev, r);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	strlcpy(priv->adap.name, "EMEV2 I2C", sizeof(priv->adap.name));
+
+	priv->sclk = devm_clk_get(&pdev->dev, "sclk");
+	if (IS_ERR(priv->sclk))
+		return PTR_ERR(priv->sclk);
+
+	clk_prepare_enable(priv->sclk);
+
+	priv->adap.timeout = msecs_to_jiffies(100);
+	priv->adap.retries = 5;
+	priv->adap.dev.parent = &pdev->dev;
+	priv->adap.algo = &em_i2c_algo;
+	priv->adap.owner = THIS_MODULE;
+	priv->adap.dev.of_node = pdev->dev.of_node;
+
+	init_completion(&priv->msg_done);
+
+	platform_set_drvdata(pdev, priv);
+	i2c_set_adapdata(&priv->adap, priv);
+
+	em_i2c_reset(&priv->adap);
+
+	irq = platform_get_irq(pdev, 0);
+	ret = devm_request_irq(&pdev->dev, irq, em_i2c_irq_handler, 0,
+				"em_i2c", priv);
+	if (ret)
+		goto err_clk;
+
+	ret = i2c_add_adapter(&priv->adap);
+
+	if (ret)
+		goto err_clk;
+
+	dev_info(&pdev->dev, "Added i2c controller %d, irq %d\n", priv->adap.nr, irq);
+
+	return 0;
+
+err_clk:
+	clk_disable_unprepare(priv->sclk);
+	return ret;
+}
+
+static int em_i2c_remove(struct platform_device *dev)
+{
+	struct em_i2c_device *priv = platform_get_drvdata(dev);
+
+	i2c_del_adapter(&priv->adap);
+	clk_disable_unprepare(priv->sclk);
+
+	return 0;
+}
+
+static const struct of_device_id em_i2c_ids[] = {
+	{ .compatible = "renesas,iic-emev2", },
+	{ }
+};
+
+static struct platform_driver em_i2c_driver = {
+	.probe = em_i2c_probe,
+	.remove = em_i2c_remove,
+	.driver = {
+		.name = "em-i2c",
+		.of_match_table = em_i2c_ids,
+	}
+};
+module_platform_driver(em_i2c_driver);
+
+MODULE_DESCRIPTION("EMEV2 I2C bus driver");
+MODULE_AUTHOR("Ian Molton and Wolfram Sang <wsa@sang-engineering.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_DEVICE_TABLE(of, em_i2c_ids);