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@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
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@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@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@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, +};