From mboxrd@z Thu Jan  1 00:00:00 1970
From: Przemyslaw Marczak <p.marczak@samsung.com>
Date: Fri, 27 Mar 2015 18:33:44 +0100
Subject: [U-Boot] [PATCH V2 3/3] dm: i2c: add i2c-gpio driver
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This commit adds driver model support to software emulated i2c bus driver.
The device-tree node is compatible with the kernel i2c-gpio driver. It means,
that boards device-tree "i2c-gpio" node, should be the same as in the kernel.
For operating, it requires proper compatible and gpio pins dts description.
Added:
- Config: CONFIG_DM_I2C_GPIO
- File: drivers/i2c/i2c-gpio.c
- File: doc/device-tree-bindings/i2c/i2c-gpio.txt

Driver base code is taken from: drivers/i2c/soft-i2c.c, changes:
- update comments style,
- move preprocesor macros into functions,
- add device-tree support,
- add driver model i2c support.
- add Kconfig entry

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
CC: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Lukasz Majewski <l.majewski@samsung.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Simon Glass <sjg@chromium.org>
Cc: Heiko Schocher <hs@denx.de>

Changes V2:
- new file for software i2c driver: i2c-gpio.c
- update driver naming: use of "i2c-gpio"
- add full compatibility with the kernels device-tree "i2c-gpio" node
- fix Kconfig entry
---
 doc/device-tree-bindings/i2c/i2c-gpio.txt |  37 ++++
 drivers/i2c/Kconfig                       |   9 +
 drivers/i2c/Makefile                      |   1 +
 drivers/i2c/i2c-gpio.c                    | 353 ++++++++++++++++++++++++++++++
 4 files changed, 400 insertions(+)
 create mode 100644 doc/device-tree-bindings/i2c/i2c-gpio.txt
 create mode 100644 drivers/i2c/i2c-gpio.c

diff --git a/doc/device-tree-bindings/i2c/i2c-gpio.txt b/doc/device-tree-bindings/i2c/i2c-gpio.txt
new file mode 100644
index 0000000..3978381
--- /dev/null
+++ b/doc/device-tree-bindings/i2c/i2c-gpio.txt
@@ -0,0 +1,37 @@
+I2C gpio device binding
+=======================
+
+Driver:
+- drivers/i2c/i2c-gpio.c
+
+Software i2c device-tree node properties:
+Required:
+* #address-cells = <1>;
+* #size-cells = <0>;
+* compatible = "i2c-gpio";
+* gpios = <sda ...>, <scl ...>;
+
+Optional:
+* i2c-gpio,delay-us = <5>;
+   The resulting transfer speed can be adjusted by setting the delay[us]
+   between gpio-toggle operations. Speed [Hz] = 1us / 4 * udelay,
+   It not defined, then default is 5us (~50KHz).
+
+Example:
+
+i2c-gpio at 1 {
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	compatible = "i2c-gpio";
+	gpios = <&gpd1 0 GPIO_ACTIVE_HIGH>, /* SDA */
+		<&gpd1 1 GPIO_ACTIVE_HIGH>; /* CLK */
+
+	i2c-gpio,delay-us = <5>;
+
+	some_device at 5 {
+		compatible = "some_device";
+		reg = <0x5>;
+		...
+	};
+};
diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index 979522f..22e4a7c 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -19,6 +19,15 @@ config DM_I2C_COMPAT
 	  to convert all code for a board in a single commit. It should not
 	  be enabled for any board in an official release.
 
+config DM_I2C_GPIO
+	bool "Enable Driver Model for software emulated I2C bus driver"
+	depends on DM_I2C && DM_GPIO
+	help
+	  Enable the i2c bus driver emulation by using the GPIO.
+	  The bus gpio configuration is given by the device-tree.
+	  Kernel style device-tree node for i2c-gpio is supported.
+	  Binding info: doc/device-tree-bindings/i2c/i2c-gpio.txt
+
 config SYS_I2C_UNIPHIER
 	bool "UniPhier I2C driver"
 	depends on ARCH_UNIPHIER && DM_I2C
diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
index 774bc94..d9e9f3a 100644
--- a/drivers/i2c/Makefile
+++ b/drivers/i2c/Makefile
@@ -6,6 +6,7 @@
 #
 obj-$(CONFIG_DM_I2C) += i2c-uclass.o
 obj-$(CONFIG_DM_I2C_COMPAT) += i2c-uclass-compat.o
+obj-$(CONFIG_DM_I2C_GPIO) += i2c-gpio.o
 
 obj-$(CONFIG_SYS_I2C_ADI) += adi_i2c.o
 obj-$(CONFIG_I2C_MV) += mv_i2c.o
diff --git a/drivers/i2c/i2c-gpio.c b/drivers/i2c/i2c-gpio.c
new file mode 100644
index 0000000..8e9ed6b
--- /dev/null
+++ b/drivers/i2c/i2c-gpio.c
@@ -0,0 +1,353 @@
+/*
+ * (C) Copyright 2015, Samsung Electronics
+ * Przemyslaw Marczak <p.marczak@samsung.com>
+ * Add driver-model support as a separated driver file
+ *
+ * (C) Copyright 2009
+ * Heiko Schocher, DENX Software Engineering, hs at denx.de.
+ * Changes for multibus/multiadapter I2C support.
+ *
+ * (C) Copyright 2001, 2002
+ * Wolfgang Denk, DENX Software Engineering, wd at denx.de.
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ *
+ * This has been changed substantially by Gerald Van Baren, Custom IDEAS,
+ * vanbaren at cideas.com.  It was heavily influenced by LiMon, written by
+ * Neil Russell.
+ */
+#include <common.h>
+#include <errno.h>
+#include <dm.h>
+#include <i2c.h>
+#include <div64.h>
+#include <asm/gpio.h>
+
+#define DEFAULT_UDELAY	5
+#define RETRIES		0
+#define I2C_ACK		0
+#define I2C_NOACK	1
+
+#ifdef DEBUG_I2C
+#define PRINTD(fmt, args...)	do {	\
+		printf (fmt, ##args);	\
+	} while (0)
+#else
+#define PRINTD(fmt, args...)
+#endif
+
+DECLARE_GLOBAL_DATA_PTR;
+
+enum {
+	PIN_SDA = 0,
+	PIN_SCL,
+};
+
+struct i2c_gpio_bus {
+	unsigned int speed;
+	unsigned long udelay;
+	struct gpio_desc gpios[2]; /* sda, scl */
+};
+
+/* Local functions */
+static void send_reset(struct gpio_desc *, struct gpio_desc *, int);
+static void send_start(struct gpio_desc *, struct gpio_desc *, int);
+static void send_stop(struct gpio_desc *, struct gpio_desc *, int);
+static void send_ack(struct gpio_desc *, struct gpio_desc *, int, int);
+static int write_byte(struct gpio_desc *, struct gpio_desc *, int, uchar);
+static uchar read_byte(struct gpio_desc *, struct gpio_desc *, int, int);
+
+static int I2C_READ(struct gpio_desc *sda)
+{
+	return dm_gpio_get_value(sda);
+}
+
+static void I2C_SDA(struct gpio_desc *sda, int bit)
+{
+	if (bit) {
+		dm_gpio_set_dir_flags(sda, GPIOD_IS_IN);
+	} else {
+		dm_gpio_set_dir_flags(sda, GPIOD_IS_OUT);
+		dm_gpio_set_value(sda, 0);
+	}
+}
+
+static void I2C_SCL(struct gpio_desc *scl, int bit)
+{
+	dm_gpio_set_dir_flags(scl, GPIOD_IS_OUT);
+	dm_gpio_set_value(scl, bit);
+}
+
+static void I2C_DELAY(unsigned long us)
+{
+	udelay(us);	/* 1/4 I2C clock duration */
+}
+
+/**
+ * Send a reset sequence consisting of 9 clocks with the data signal high
+ * to clock any confused device back into an idle state.  Also send a
+ * <stop> at the end of the sequence for belts & suspenders.
+ */
+static void send_reset(struct gpio_desc *scl, struct gpio_desc *sda, int delay)
+{
+	int j;
+
+	I2C_SCL(scl, 1);
+	I2C_SDA(sda, 1);
+
+	for (j = 0; j < 9; j++) {
+		I2C_SCL(scl, 0);
+		I2C_DELAY(delay);
+		I2C_DELAY(delay);
+		I2C_SCL(scl, 1);
+		I2C_DELAY(delay);
+		I2C_DELAY(delay);
+	}
+	send_stop(scl, sda, delay);
+}
+
+/* START: High -> Low on SDA while SCL is High */
+static void send_start(struct gpio_desc *scl, struct gpio_desc *sda, int delay)
+{
+	I2C_DELAY(delay);
+	I2C_SDA(sda, 1);
+	I2C_DELAY(delay);
+	I2C_SCL(scl, 1);
+	I2C_DELAY(delay);
+	I2C_SDA(sda, 0);
+	I2C_DELAY(delay);
+}
+
+/* STOP: Low -> High on SDA while SCL is High */
+static void send_stop(struct gpio_desc *scl, struct gpio_desc *sda, int delay)
+{
+	I2C_SCL(scl, 0);
+	I2C_DELAY(delay);
+	I2C_SDA(sda, 0);
+	I2C_DELAY(delay);
+	I2C_SCL(scl, 1);
+	I2C_DELAY(delay);
+	I2C_SDA(sda, 1);
+	I2C_DELAY(delay);
+}
+
+/* ack should be I2C_ACK or I2C_NOACK */
+static void send_ack(struct gpio_desc *scl, struct gpio_desc *sda,
+		     int delay, int ack)
+{
+	I2C_SCL(scl, 0);
+	I2C_DELAY(delay);
+	I2C_SDA(sda, ack);
+	I2C_DELAY(delay);
+	I2C_SCL(scl, 1);
+	I2C_DELAY(delay);
+	I2C_DELAY(delay);
+	I2C_SCL(scl, 0);
+	I2C_DELAY(delay);
+}
+
+/* Send 8 bits and look for an acknowledgement */
+static int write_byte(struct gpio_desc *scl, struct gpio_desc *sda,
+		      int delay, uchar data)
+{
+	int j;
+	int nack;
+
+	for (j = 0; j < 8; j++) {
+		I2C_SCL(scl, 0);
+		I2C_DELAY(delay);
+		I2C_SDA(sda, data & 0x80);
+		I2C_DELAY(delay);
+		I2C_SCL(scl, 1);
+		I2C_DELAY(delay);
+		I2C_DELAY(delay);
+
+		data <<= 1;
+	}
+
+	/* Look for an <ACK>(negative logic) and return it */
+	I2C_SCL(scl, 0);
+	I2C_DELAY(delay);
+	I2C_SDA(sda, 1);
+	I2C_DELAY(delay);
+	I2C_SCL(scl, 1);
+	I2C_DELAY(delay);
+	I2C_DELAY(delay);
+	nack = I2C_READ(sda);
+	I2C_SCL(scl, 0);
+	I2C_DELAY(delay);
+
+	return nack;	/* not a nack is an ack */
+}
+
+/**
+ * if ack == I2C_ACK, ACK the byte so can continue reading, else
+ * send I2C_NOACK to end the read.
+ */
+static uchar read_byte(struct gpio_desc *scl, struct gpio_desc *sda,
+		       int delay, int ack)
+{
+	int  data;
+	int  j;
+
+	/* Read 8 bits, MSB first */
+	I2C_SDA(sda, 1);
+	data = 0;
+	for (j = 0; j < 8; j++) {
+		I2C_SCL(scl, 0);
+		I2C_DELAY(delay);
+		I2C_SCL(scl, 1);
+		I2C_DELAY(delay);
+		data <<= 1;
+		data |= I2C_READ(sda);
+		I2C_DELAY(delay);
+	}
+	send_ack(scl, sda, delay, ack);
+
+	return data;
+}
+
+static int i2c_write_data(struct i2c_gpio_bus *bus, uchar chip,
+			  uchar *buffer, int len, bool end_with_repeated_start)
+{
+	struct gpio_desc *scl = &bus->gpios[PIN_SCL];
+	struct gpio_desc *sda = &bus->gpios[PIN_SDA];
+	unsigned int delay = bus->udelay;
+	int failures = 0;
+
+	PRINTD("%s: chip %x buffer %p len %d\n", __func__, chip, buffer, len);
+
+	send_start(scl, sda, delay);
+	if (write_byte(scl, sda, delay, chip << 1)) {
+		send_stop(scl, sda, delay);
+		PRINTD("i2c_write, no chip responded %02X\n", chip);
+		return -EIO;
+	}
+
+	while (len-- > 0) {
+		if (write_byte(scl, sda, delay, *buffer++))
+			failures++;
+	}
+
+	send_stop(scl, sda, delay);
+
+	return failures;
+}
+
+static int i2c_read_data(struct i2c_gpio_bus *bus, uchar chip,
+			 uchar *buffer, int len)
+{
+	struct gpio_desc *scl = &bus->gpios[PIN_SCL];
+	struct gpio_desc *sda = &bus->gpios[PIN_SDA];
+	unsigned int delay = bus->udelay;
+
+	PRINTD("%s: chip %x buffer: %x len %d\n", __func__, chip, buffer, len);
+
+	send_start(scl, sda, delay);
+	write_byte(scl, sda, delay, (chip << 1) | 1);	/* read cycle */
+
+	while (len-- > 0)
+		*buffer++ = read_byte(scl, sda, delay, len == 0);
+
+	send_stop(scl, sda, delay);
+
+	return 0;
+}
+
+static int i2c_gpio_xfer(struct udevice *dev, struct i2c_msg *msg, int nmsgs)
+{
+	struct i2c_gpio_bus *bus = dev_get_priv(dev);
+	int ret;
+
+	for (; nmsgs > 0; nmsgs--, msg++) {
+		bool next_is_read = nmsgs > 1 && (msg[1].flags & I2C_M_RD);
+		if (msg->flags & I2C_M_RD)
+			ret = i2c_read_data(bus, msg->addr, msg->buf, msg->len);
+		else
+			ret = i2c_write_data(bus, msg->addr, msg->buf, msg->len,
+					     next_is_read);
+
+		if (ret)
+			return -EREMOTEIO;
+	}
+
+	return 0;
+}
+
+static int i2c_gpio_probe(struct udevice *dev, uint chip, uint chip_flags)
+{
+	struct i2c_gpio_bus *bus = dev_get_priv(dev);
+	struct gpio_desc *scl = &bus->gpios[PIN_SCL];
+	struct gpio_desc *sda = &bus->gpios[PIN_SDA];
+	unsigned int delay = bus->udelay;
+	int ret;
+
+	send_start(scl, sda, delay);
+	ret = write_byte(scl, sda, delay, (chip << 1) | 0);
+	send_stop(scl, sda, delay);
+
+	PRINTD("%s: bus: %d (%s) chip: %x flags: %x ret: %d\n",
+	       __func__, dev->seq, dev->name, chip, chip_flags, ret);
+
+	return ret;
+}
+
+static int i2c_gpio_set_bus_speed(struct udevice *dev, unsigned int speed)
+{
+	struct i2c_gpio_bus *bus = dev_get_priv(dev);
+	struct gpio_desc *scl = &bus->gpios[PIN_SCL];
+	struct gpio_desc *sda = &bus->gpios[PIN_SDA];
+
+	bus->speed = speed;
+	bus->udelay = lldiv(1000000, speed << 2);
+
+	send_reset(scl, sda, bus->udelay);
+
+	PRINTD("%s: bus: %d (%s) speed: %u Hz (1/4 of period: %lu us)\n",
+	       __func__, dev->seq, dev->name, speed, bus->udelay);
+
+	return 0;
+}
+
+static int i2c_gpio_ofdata_to_platdata(struct udevice *dev)
+{
+	struct i2c_gpio_bus *bus = dev_get_priv(dev);
+	const void *blob = gd->fdt_blob;
+	int node = dev->of_offset;
+	int ret;
+
+	ret = gpio_request_list_by_name(dev, "gpios", bus->gpios,
+					ARRAY_SIZE(bus->gpios), 0);
+	if (ret < 0)
+		goto error;
+
+	bus->udelay = fdtdec_get_int(blob, node, "i2c-gpio,delay-us",
+				     DEFAULT_UDELAY);
+
+	PRINTD("%s: bus: %d (%s) fdt node ok\n", __func__, dev->seq, dev->name);
+
+	return 0;
+error:
+	error("Can't get %s gpios! Error: %d", dev->name, ret);
+	return ret;
+}
+
+static const struct dm_i2c_ops i2c_gpio_ops = {
+	.xfer		= i2c_gpio_xfer,
+	.probe_chip	= i2c_gpio_probe,
+	.set_bus_speed	= i2c_gpio_set_bus_speed,
+};
+
+static const struct udevice_id i2c_gpio_ids[] = {
+	{ .compatible = "i2c-gpio" },
+	{ }
+};
+
+U_BOOT_DRIVER(i2c_gpio) = {
+	.name	= "i2c-gpio",
+	.id	= UCLASS_I2C,
+	.of_match = i2c_gpio_ids,
+	.ofdata_to_platdata = i2c_gpio_ofdata_to_platdata,
+	.priv_auto_alloc_size = sizeof(struct i2c_gpio_bus),
+	.ops	= &i2c_gpio_ops,
+};
-- 
1.9.1