[U-Boot] [PATCH V3 3/3] dm: i2c: add i2c-gpio driver
Przemyslaw Marczak
p.marczak at samsung.com
Tue Mar 31 18:57:18 CEST 2015
This commit adds driver model support to software emulated i2c bus driver.
This driver supports kernel-style device tree bindings. Fdt properties in use:
- compatible - "i2c-gpio"
- gpios - data and clock GPIO pin phandles
- delay-us - micro seconds delay between GPIOs toggle operations,
which is 1/4 of I2C speed clock period.
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:
- use "i2c-gpio" naming
- update comments style
- move preprocesor macros into functions
- add device tree support
- add driver model i2c support
- code cleanup,
- add Kconfig entry
Signed-off-by: Przemyslaw Marczak <p.marczak at samsung.com>
CC: Masahiro Yamada <yamada.masahiro at socionext.com>
Cc: Lukasz Majewski <l.majewski at samsung.com>
Cc: Mike Frysinger <vapier at gentoo.org>
Cc: Simon Glass <sjg at chromium.org>
Cc: Heiko Schocher <hs at 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
Changes V3:
- fix Kconfig entry
- update file header
- remove field "speed" from struct i2c_gpio_bus
- move macros to functions
- move duplicated routines into functions
- update naming with prefix "i2c_gpio_"
---
doc/device-tree-bindings/i2c/i2c-gpio.txt | 37 ++++
drivers/i2c/Kconfig | 9 +
drivers/i2c/Makefile | 1 +
drivers/i2c/i2c-gpio.c | 345 ++++++++++++++++++++++++++++++
4 files changed, 392 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..ba56ed5
--- /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] = 1000000 / 4 * udelay[us],
+ 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 c83a984..739badc 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 GPIOs. The bus GPIO
+ configuration is given by the device tree. Kernel-style device tree
+ bindings are 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..f17839b
--- /dev/null
+++ b/drivers/i2c/i2c-gpio.c
@@ -0,0 +1,345 @@
+/*
+ * (C) Copyright 2015, Samsung Electronics
+ * Przemyslaw Marczak <p.marczak at samsung.com>
+ *
+ * This file is based on: drivers/i2c/soft-i2c.c,
+ * with added driver-model support and code cleanup.
+ */
+#include <common.h>
+#include <errno.h>
+#include <dm.h>
+#include <i2c.h>
+#include <asm/gpio.h>
+
+#define DEFAULT_UDELAY 5
+#define RETRIES 0
+#define I2C_ACK 0
+#define I2C_NOACK 1
+
+DECLARE_GLOBAL_DATA_PTR;
+
+enum {
+ PIN_SDA = 0,
+ PIN_SCL,
+ PIN_COUNT,
+};
+
+struct i2c_gpio_bus {
+ /**
+ * udelay - delay [us] between GPIO toggle operations,
+ * which is 1/4 of I2C speed clock period.
+ */
+ int udelay;
+ /* sda, scl */
+ struct gpio_desc gpios[PIN_COUNT];
+};
+
+static int i2c_gpio_sda_get(struct gpio_desc *sda)
+{
+ return dm_gpio_get_value(sda);
+}
+
+static void i2c_gpio_sda_set(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_gpio_scl_set(struct gpio_desc *scl, int bit)
+{
+ dm_gpio_set_dir_flags(scl, GPIOD_IS_OUT);
+ dm_gpio_set_value(scl, bit);
+}
+
+static void i2c_gpio_write_bit(struct gpio_desc *scl, struct gpio_desc *sda,
+ int delay, uchar bit)
+{
+ i2c_gpio_scl_set(scl, 0);
+ udelay(delay);
+ i2c_gpio_sda_set(sda, bit);
+ udelay(delay);
+ i2c_gpio_scl_set(scl, 1);
+ udelay(2 * delay);
+}
+
+static int i2c_gpio_read_bit(struct gpio_desc *scl, struct gpio_desc *sda,
+ int delay)
+{
+ int value;
+
+ i2c_gpio_scl_set(scl, 1);
+ udelay(delay);
+ value = i2c_gpio_sda_get(sda);
+ udelay(delay);
+ i2c_gpio_scl_set(scl, 0);
+ udelay(2 * delay);
+
+ return value;
+}
+
+/* START: High -> Low on SDA while SCL is High */
+static void i2c_gpio_send_start(struct gpio_desc *scl, struct gpio_desc *sda,
+ int delay)
+{
+ udelay(delay);
+ i2c_gpio_sda_set(sda, 1);
+ udelay(delay);
+ i2c_gpio_scl_set(scl, 1);
+ udelay(delay);
+ i2c_gpio_sda_set(sda, 0);
+ udelay(delay);
+}
+
+/* STOP: Low -> High on SDA while SCL is High */
+static void i2c_gpio_send_stop(struct gpio_desc *scl, struct gpio_desc *sda,
+ int delay)
+{
+ i2c_gpio_scl_set(scl, 0);
+ udelay(delay);
+ i2c_gpio_sda_set(sda, 0);
+ udelay(delay);
+ i2c_gpio_scl_set(scl, 1);
+ udelay(delay);
+ i2c_gpio_sda_set(sda, 1);
+ udelay(delay);
+}
+
+/* ack should be I2C_ACK or I2C_NOACK */
+static void i2c_gpio_send_ack(struct gpio_desc *scl, struct gpio_desc *sda,
+ int delay, int ack)
+{
+ i2c_gpio_write_bit(scl, sda, delay, ack);
+ i2c_gpio_scl_set(scl, 0);
+ udelay(delay);
+}
+
+/**
+ * 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 i2c_gpio_send_reset(struct gpio_desc *scl, struct gpio_desc *sda,
+ int delay)
+{
+ int j;
+
+ for (j = 0; j < 9; j++)
+ i2c_gpio_write_bit(scl, sda, delay, 1);
+
+ i2c_gpio_send_stop(scl, sda, delay);
+}
+
+/* Set sda high with low clock, before reading slave data */
+static void i2c_gpio_sda_high(struct gpio_desc *scl, struct gpio_desc *sda,
+ int delay)
+{
+ i2c_gpio_scl_set(scl, 0);
+ udelay(delay);
+ i2c_gpio_sda_set(sda, 1);
+ udelay(delay);
+}
+
+/* Send 8 bits and look for an acknowledgement */
+static int i2c_gpio_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_gpio_write_bit(scl, sda, delay, data & 0x80);
+ data <<= 1;
+ }
+
+ udelay(delay);
+
+ /* Look for an <ACK>(negative logic) and return it */
+ i2c_gpio_sda_high(scl, sda, delay);
+ nack = i2c_gpio_read_bit(scl, sda, 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 i2c_gpio_read_byte(struct gpio_desc *scl, struct gpio_desc *sda,
+ int delay, int ack)
+{
+ int data;
+ int j;
+
+ i2c_gpio_sda_high(scl, sda, delay);
+ data = 0;
+ for (j = 0; j < 8; j++) {
+ data <<= 1;
+ data |= i2c_gpio_read_bit(scl, sda, delay);
+ }
+ i2c_gpio_send_ack(scl, sda, delay, ack);
+
+ return data;
+}
+
+/* send start and the slave chip address */
+int i2c_send_slave_addr(struct gpio_desc *scl, struct gpio_desc *sda, int delay,
+ uchar chip)
+{
+ i2c_gpio_send_start(scl, sda, delay);
+
+ if (i2c_gpio_write_byte(scl, sda, delay, chip)) {
+ i2c_gpio_send_stop(scl, sda, delay);
+ return -EIO;
+ }
+
+ return 0;
+}
+
+static int i2c_gpio_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;
+
+ debug("%s: chip %x buffer %p len %d\n", __func__, chip, buffer, len);
+
+ if (i2c_send_slave_addr(scl, sda, delay, chip << 1)) {
+ debug("i2c_write, no chip responded %02X\n", chip);
+ return -EIO;
+ }
+
+ while (len-- > 0) {
+ if (i2c_gpio_write_byte(scl, sda, delay, *buffer++))
+ failures++;
+ }
+
+ if (!end_with_repeated_start) {
+ i2c_gpio_send_stop(scl, sda, delay);
+ return failures;
+ }
+
+ if (i2c_send_slave_addr(scl, sda, delay, (chip << 1) | 0x1)) {
+ debug("i2c_write, no chip responded %02X\n", chip);
+ return -EIO;
+ }
+
+ return failures;
+}
+
+static int i2c_gpio_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;
+
+ debug("%s: chip %x buffer: %p len %d\n", __func__, chip, buffer, len);
+
+ while (len-- > 0)
+ *buffer++ = i2c_gpio_read_byte(scl, sda, delay, len == 0);
+
+ i2c_gpio_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_gpio_read_data(bus, msg->addr, msg->buf,
+ msg->len);
+ else
+ ret = i2c_gpio_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;
+
+ i2c_gpio_send_start(scl, sda, delay);
+ ret = i2c_gpio_write_byte(scl, sda, delay, (chip << 1) | 0);
+ i2c_gpio_send_stop(scl, sda, delay);
+
+ debug("%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_hz)
+{
+ 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->udelay = 1000000 / (speed_hz << 2);
+
+ i2c_gpio_send_reset(scl, sda, 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);
+
+ 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
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