Commit c54473cb authored by Przemyslaw Marczak's avatar Przemyslaw Marczak Committed by Simon Glass
Browse files

dm: i2c: add i2c-gpio driver



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: default avatarPrzemyslaw Marczak <p.marczak@samsung.com>
Acked-by: default avatarSimon Glass <sjg@chromium.org>
Added braces in i2c_gpio_xfer() to fix style nit:
Signed-off-by: default avatarSimon Glass <sjg@chromium.org>
parent 705fcf4d
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>;
...
};
};
......@@ -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
......
......@@ -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
......
/*
* (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,
};
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