i2c: riic: add driver

Tested with a r7s72100 genmai board acessing an eeprom.
Signed-off-by: NWolfram Sang <wsa@sang-engineering.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

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

+Device tree configuration for Renesas RIIC driver
+
+Required properties:
+- compatible      : "renesas,riic-<soctype>". "renesas,riic-rz" as fallback
+- reg             : address start and address range size of device
+- interrupts      : 8 interrupts (TEI, RI, TI, SPI, STI, NAKI, ALI, TMOI)
+- clock-frequency : frequency of bus clock in Hz
+- #address-cells  : should be <1>
+- #size-cells     : should be <0>
+
+Pinctrl properties might be needed, too. See there.
+
+Example:
+
+	i2c0: i2c@fcfee000 {
+		compatible = "renesas,riic-r7s72100", "renesas,riic-rz";
+		reg = <0xfcfee000 0x44>;
+		interrupts = <0 157 IRQ_TYPE_LEVEL_HIGH>,
+			     <0 158 IRQ_TYPE_EDGE_RISING>,
+			     <0 159 IRQ_TYPE_EDGE_RISING>,
+			     <0 160 IRQ_TYPE_LEVEL_HIGH>,
+			     <0 161 IRQ_TYPE_LEVEL_HIGH>,
+			     <0 162 IRQ_TYPE_LEVEL_HIGH>,
+			     <0 163 IRQ_TYPE_LEVEL_HIGH>,
+			     <0 164 IRQ_TYPE_LEVEL_HIGH>;
+		clock-frequency = <100000>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+	};

drivers/i2c/busses/Kconfig

@@ -648,6 +648,16 @@ config I2C_PXA_SLAVE
 	  is necessary for systems where the PXA may be a target on the
 	  I2C bus.
 
+config I2C_RIIC
+	tristate "Renesas RIIC adapter"
+	depends on ARCH_SHMOBILE || COMPILE_TEST
+	help
+	  If you say yes to this option, support will be included for the
+	  Renesas RIIC I2C interface.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called i2c-riic.
+
 config HAVE_S3C2410_I2C
 	bool
 	help

drivers/i2c/busses/Makefile

@@ -63,6 +63,7 @@ obj-$(CONFIG_I2C_PNX)		+= i2c-pnx.o
 obj-$(CONFIG_I2C_PUV3)		+= i2c-puv3.o
 obj-$(CONFIG_I2C_PXA)		+= i2c-pxa.o
 obj-$(CONFIG_I2C_PXA_PCI)	+= i2c-pxa-pci.o
+obj-$(CONFIG_I2C_RIIC)		+= i2c-riic.o
 obj-$(CONFIG_I2C_S3C2410)	+= i2c-s3c2410.o
 obj-$(CONFIG_I2C_S6000)		+= i2c-s6000.o
 obj-$(CONFIG_I2C_SH7760)	+= i2c-sh7760.o

drivers/i2c/busses/i2c-riic.c

+/*
+ * Renesas RIIC driver
+ *
+ * Copyright (C) 2013 Wolfram Sang <wsa@sang-engineering.com>
+ * Copyright (C) 2013 Renesas Solutions Corp.
+ *
+ * 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.
+ */
+
+/*
+ * This i2c core has a lot of interrupts, namely 8. We use their chaining as
+ * some kind of state machine.
+ *
+ * 1) The main xfer routine kicks off a transmission by putting the start bit
+ * (or repeated start) on the bus and enabling the transmit interrupt (TIE)
+ * since we need to send the slave address + RW bit in every case.
+ *
+ * 2) TIE sends slave address + RW bit and selects how to continue.
+ *
+ * 3a) Write case: We keep utilizing TIE as long as we have data to send. If we
+ * are done, we switch over to the transmission done interrupt (TEIE) and mark
+ * the message as completed (includes sending STOP) there.
+ *
+ * 3b) Read case: We switch over to receive interrupt (RIE). One dummy read is
+ * needed to start clocking, then we keep receiving until we are done. Note
+ * that we use the RDRFS mode all the time, i.e. we ACK/NACK every byte by
+ * writing to the ACKBT bit. I tried using the RDRFS mode only at the end of a
+ * message to create the final NACK as sketched in the datasheet. This caused
+ * some subtle races (when byte n was processed and byte n+1 was already
+ * waiting), though, and I started with the safe approach.
+ *
+ * 4) If we got a NACK somewhere, we flag the error and stop the transmission
+ * via NAKIE.
+ *
+ * Also check the comments in the interrupt routines for some gory details.
+ */
+
+#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.h>
+#include <linux/platform_device.h>
+
+#define RIIC_ICCR1	0x00
+#define RIIC_ICCR2	0x04
+#define RIIC_ICMR1	0x08
+#define RIIC_ICMR3	0x10
+#define RIIC_ICSER	0x18
+#define RIIC_ICIER	0x1c
+#define RIIC_ICSR2	0x24
+#define RIIC_ICBRL	0x34
+#define RIIC_ICBRH	0x38
+#define RIIC_ICDRT	0x3c
+#define RIIC_ICDRR	0x40
+
+#define ICCR1_ICE	0x80
+#define ICCR1_IICRST	0x40
+#define ICCR1_SOWP	0x10
+
+#define ICCR2_BBSY	0x80
+#define ICCR2_SP	0x08
+#define ICCR2_RS	0x04
+#define ICCR2_ST	0x02
+
+#define ICMR1_CKS_MASK	0x70
+#define ICMR1_BCWP	0x08
+#define ICMR1_CKS(_x)	((((_x) << 4) & ICMR1_CKS_MASK) | ICMR1_BCWP)
+
+#define ICMR3_RDRFS	0x20
+#define ICMR3_ACKWP	0x10
+#define ICMR3_ACKBT	0x08
+
+#define ICIER_TIE	0x80
+#define ICIER_TEIE	0x40
+#define ICIER_RIE	0x20
+#define ICIER_NAKIE	0x10
+
+#define ICSR2_NACKF	0x10
+
+/* ICBRx (@ PCLK 33MHz) */
+#define ICBR_RESERVED	0xe0 /* Should be 1 on writes */
+#define ICBRL_SP100K	(19 | ICBR_RESERVED)
+#define ICBRH_SP100K	(16 | ICBR_RESERVED)
+#define ICBRL_SP400K	(21 | ICBR_RESERVED)
+#define ICBRH_SP400K	(9 | ICBR_RESERVED)
+
+#define RIIC_INIT_MSG	-1
+
+struct riic_dev {
+	void __iomem *base;
+	u8 *buf;
+	struct i2c_msg *msg;
+	int bytes_left;
+	int err;
+	int is_last;
+	struct completion msg_done;
+	struct i2c_adapter adapter;
+	struct clk *clk;
+};
+
+struct riic_irq_desc {
+	int res_num;
+	irq_handler_t isr;
+	char *name;
+};
+
+static inline void riic_clear_set_bit(struct riic_dev *riic, u8 clear, u8 set, u8 reg)
+{
+	writeb((readb(riic->base + reg) & ~clear) | set, riic->base + reg);
+}
+
+static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
+{
+	struct riic_dev *riic = i2c_get_adapdata(adap);
+	unsigned long time_left;
+	int i, ret;
+	u8 start_bit;
+
+	ret = clk_prepare_enable(riic->clk);
+	if (ret)
+		return ret;
+
+	if (readb(riic->base + RIIC_ICCR2) & ICCR2_BBSY) {
+		riic->err = -EBUSY;
+		goto out;
+	}
+
+	reinit_completion(&riic->msg_done);
+	riic->err = 0;
+
+	writeb(0, riic->base + RIIC_ICSR2);
+
+	for (i = 0, start_bit = ICCR2_ST; i < num; i++) {
+		riic->bytes_left = RIIC_INIT_MSG;
+		riic->buf = msgs[i].buf;
+		riic->msg = &msgs[i];
+		riic->is_last = (i == num - 1);
+
+		writeb(ICIER_NAKIE | ICIER_TIE, riic->base + RIIC_ICIER);
+
+		writeb(start_bit, riic->base + RIIC_ICCR2);
+
+		time_left = wait_for_completion_timeout(&riic->msg_done, riic->adapter.timeout);
+		if (time_left == 0)
+			riic->err = -ETIMEDOUT;
+
+		if (riic->err)
+			break;
+
+		start_bit = ICCR2_RS;
+	}
+
+ out:
+	clk_disable_unprepare(riic->clk);
+
+	return riic->err ?: num;
+}
+
+static irqreturn_t riic_tdre_isr(int irq, void *data)
+{
+	struct riic_dev *riic = data;
+	u8 val;
+
+	if (!riic->bytes_left)
+		return IRQ_NONE;
+
+	if (riic->bytes_left == RIIC_INIT_MSG) {
+		val = !!(riic->msg->flags & I2C_M_RD);
+		if (val)
+			/* On read, switch over to receive interrupt */
+			riic_clear_set_bit(riic, ICIER_TIE, ICIER_RIE, RIIC_ICIER);
+		else
+			/* On write, initialize length */
+			riic->bytes_left = riic->msg->len;
+
+		val |= (riic->msg->addr << 1);
+	} else {
+		val = *riic->buf;
+		riic->buf++;
+		riic->bytes_left--;
+	}
+
+	/*
+	 * Switch to transmission ended interrupt when done. Do check here
+	 * after bytes_left was initialized to support SMBUS_QUICK (new msg has
+	 * 0 length then)
+	 */
+	if (riic->bytes_left == 0)
+		riic_clear_set_bit(riic, ICIER_TIE, ICIER_TEIE, RIIC_ICIER);
+
+	/*
+	 * This acks the TIE interrupt. We get another TIE immediately if our
+	 * value could be moved to the shadow shift register right away. So
+	 * this must be after updates to ICIER (where we want to disable TIE)!
+	 */
+	writeb(val, riic->base + RIIC_ICDRT);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t riic_tend_isr(int irq, void *data)
+{
+	struct riic_dev *riic = data;
+
+	if (readb(riic->base + RIIC_ICSR2) & ICSR2_NACKF) {
+		/* We got a NACKIE */
+		readb(riic->base + RIIC_ICDRR);	/* dummy read */
+		riic->err = -ENXIO;
+	} else if (riic->bytes_left) {
+		return IRQ_NONE;
+	}
+
+	if (riic->is_last || riic->err)
+		writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
+
+	writeb(0, riic->base + RIIC_ICIER);
+	complete(&riic->msg_done);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t riic_rdrf_isr(int irq, void *data)
+{
+	struct riic_dev *riic = data;
+
+	if (!riic->bytes_left)
+		return IRQ_NONE;
+
+	if (riic->bytes_left == RIIC_INIT_MSG) {
+		riic->bytes_left = riic->msg->len;
+		readb(riic->base + RIIC_ICDRR);	/* dummy read */
+		return IRQ_HANDLED;
+	}
+
+	if (riic->bytes_left == 1) {
+		/* STOP must come before we set ACKBT! */
+		if (riic->is_last)
+			writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
+
+		riic_clear_set_bit(riic, 0, ICMR3_ACKBT, RIIC_ICMR3);
+
+		writeb(0, riic->base + RIIC_ICIER);
+		complete(&riic->msg_done);
+	} else {
+		riic_clear_set_bit(riic, ICMR3_ACKBT, 0, RIIC_ICMR3);
+	}
+
+	/* Reading acks the RIE interrupt */
+	*riic->buf = readb(riic->base + RIIC_ICDRR);
+	riic->buf++;
+	riic->bytes_left--;
+
+	return IRQ_HANDLED;
+}
+
+static u32 riic_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static const struct i2c_algorithm riic_algo = {
+	.master_xfer	= riic_xfer,
+	.functionality	= riic_func,
+};
+
+static int riic_init_hw(struct riic_dev *riic, u32 spd)
+{
+	int ret;
+	unsigned long rate;
+
+	ret = clk_prepare_enable(riic->clk);
+	if (ret)
+		return ret;
+
+	/*
+	 * TODO: Implement formula to calculate the timing values depending on
+	 * variable parent clock rate and arbitrary bus speed
+	 */
+	rate = clk_get_rate(riic->clk);
+	if (rate != 33325000) {
+		dev_err(&riic->adapter.dev,
+			"invalid parent clk (%lu). Must be 33325000Hz\n", rate);
+		clk_disable_unprepare(riic->clk);
+		return -EINVAL;
+	}
+
+	/* Changing the order of accessing IICRST and ICE may break things! */
+	writeb(ICCR1_IICRST | ICCR1_SOWP, riic->base + RIIC_ICCR1);
+	riic_clear_set_bit(riic, 0, ICCR1_ICE, RIIC_ICCR1);
+
+	switch (spd) {
+	case 100000:
+		writeb(ICMR1_CKS(3), riic->base + RIIC_ICMR1);
+		writeb(ICBRH_SP100K, riic->base + RIIC_ICBRH);
+		writeb(ICBRL_SP100K, riic->base + RIIC_ICBRL);
+		break;
+	case 400000:
+		writeb(ICMR1_CKS(1), riic->base + RIIC_ICMR1);
+		writeb(ICBRH_SP400K, riic->base + RIIC_ICBRH);
+		writeb(ICBRL_SP400K, riic->base + RIIC_ICBRL);
+		break;
+	default:
+		dev_err(&riic->adapter.dev,
+			"unsupported bus speed (%dHz). Use 100000 or 400000\n", spd);
+		clk_disable_unprepare(riic->clk);
+		return -EINVAL;
+	}
+
+	writeb(0, riic->base + RIIC_ICSER);
+	writeb(ICMR3_ACKWP | ICMR3_RDRFS, riic->base + RIIC_ICMR3);
+
+	riic_clear_set_bit(riic, ICCR1_IICRST, 0, RIIC_ICCR1);
+
+	clk_disable_unprepare(riic->clk);
+
+	return 0;
+}
+
+static struct riic_irq_desc riic_irqs[] = {
+	{ .res_num = 0, .isr = riic_tend_isr, .name = "riic-tend" },
+	{ .res_num = 1, .isr = riic_rdrf_isr, .name = "riic-rdrf" },
+	{ .res_num = 2, .isr = riic_tdre_isr, .name = "riic-tdre" },
+	{ .res_num = 5, .isr = riic_tend_isr, .name = "riic-nack" },
+};
+
+static int riic_i2c_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct riic_dev *riic;
+	struct i2c_adapter *adap;
+	struct resource *res;
+	u32 bus_rate = 0;
+	int i, ret;
+
+	riic = devm_kzalloc(&pdev->dev, sizeof(*riic), GFP_KERNEL);
+	if (!riic)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	riic->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(riic->base))
+		return PTR_ERR(riic->base);
+
+	riic->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(riic->clk)) {
+		dev_err(&pdev->dev, "missing controller clock");
+		return PTR_ERR(riic->clk);
+	}
+
+	for (i = 0; i < ARRAY_SIZE(riic_irqs); i++) {
+		res = platform_get_resource(pdev, IORESOURCE_IRQ, riic_irqs[i].res_num);
+		if (!res)
+			return -ENODEV;
+
+		ret = devm_request_irq(&pdev->dev, res->start, riic_irqs[i].isr,
+					0, riic_irqs[i].name, riic);
+		if (ret) {
+			dev_err(&pdev->dev, "failed to request irq %s\n", riic_irqs[i].name);
+			return ret;
+		}
+	}
+
+	adap = &riic->adapter;
+	i2c_set_adapdata(adap, riic);
+	strlcpy(adap->name, "Renesas RIIC adapter", sizeof(adap->name));
+	adap->owner = THIS_MODULE;
+	adap->algo = &riic_algo;
+	adap->dev.parent = &pdev->dev;
+	adap->dev.of_node = pdev->dev.of_node;
+
+	init_completion(&riic->msg_done);
+
+	of_property_read_u32(np, "clock-frequency", &bus_rate);
+	ret = riic_init_hw(riic, bus_rate);
+	if (ret)
+		return ret;
+
+
+	ret = i2c_add_adapter(adap);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to add adapter\n");
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, riic);
+
+	dev_info(&pdev->dev, "registered with %dHz bus speed\n", bus_rate);
+	return 0;
+}
+
+static int riic_i2c_remove(struct platform_device *pdev)
+{
+	struct riic_dev *riic = platform_get_drvdata(pdev);
+
+	writeb(0, riic->base + RIIC_ICIER);
+	i2c_del_adapter(&riic->adapter);
+
+	return 0;
+}
+
+static struct of_device_id riic_i2c_dt_ids[] = {
+	{ .compatible = "renesas,riic-rz" },
+	{ /* Sentinel */ },
+};
+
+static struct platform_driver riic_i2c_driver = {
+	.probe		= riic_i2c_probe,
+	.remove		= riic_i2c_remove,
+	.driver		= {
+		.name	= "i2c-riic",
+		.owner	= THIS_MODULE,
+		.of_match_table = riic_i2c_dt_ids,
+	},
+};
+
+module_platform_driver(riic_i2c_driver);
+
+MODULE_DESCRIPTION("Renesas RIIC adapter");
+MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_DEVICE_TABLE(of, riic_i2c_dt_ids);