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: Przemyslaw Marczak <p.marczak@samsung.com>
Acked-by: Simon Glass <sjg@chromium.org>
Added braces in i2c_gpio_xfer() to fix style nit:
Signed-off-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Przemyslaw Marczak
Simon Glass
parent
705fcf4de4
commit
c54473cb25
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@ -0,0 +1,37 @@
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I2C gpio device binding
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=======================
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Driver:
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- drivers/i2c/i2c-gpio.c
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Software i2c device-tree node properties:
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Required:
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* #address-cells = <1>;
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* #size-cells = <0>;
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* compatible = "i2c-gpio";
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* gpios = <sda ...>, <scl ...>;
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Optional:
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* i2c-gpio,delay-us = <5>;
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The resulting transfer speed can be adjusted by setting the delay[us]
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between gpio-toggle operations. Speed [Hz] = 1000000 / 4 * udelay[us],
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It not defined, then default is 5us (~50KHz).
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Example:
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i2c-gpio@1 {
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#address-cells = <1>;
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#size-cells = <0>;
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compatible = "i2c-gpio";
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gpios = <&gpd1 0 GPIO_ACTIVE_HIGH>, /* SDA */
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<&gpd1 1 GPIO_ACTIVE_HIGH>; /* CLK */
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i2c-gpio,delay-us = <5>;
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some_device@5 {
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compatible = "some_device";
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reg = <0x5>;
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...
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};
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};
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@ -19,6 +19,15 @@ config DM_I2C_COMPAT
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to convert all code for a board in a single commit. It should not
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be enabled for any board in an official release.
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config DM_I2C_GPIO
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bool "Enable Driver Model for software emulated I2C bus driver"
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depends on DM_I2C && DM_GPIO
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help
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Enable the i2c bus driver emulation by using the GPIOs. The bus GPIO
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configuration is given by the device tree. Kernel-style device tree
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bindings are supported.
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Binding info: doc/device-tree-bindings/i2c/i2c-gpio.txt
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config SYS_I2C_UNIPHIER
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bool "UniPhier I2C driver"
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depends on ARCH_UNIPHIER && DM_I2C
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@ -6,6 +6,7 @@
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#
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obj-$(CONFIG_DM_I2C) += i2c-uclass.o
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obj-$(CONFIG_DM_I2C_COMPAT) += i2c-uclass-compat.o
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obj-$(CONFIG_DM_I2C_GPIO) += i2c-gpio.o
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obj-$(CONFIG_SYS_I2C_ADI) += adi_i2c.o
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obj-$(CONFIG_I2C_MV) += mv_i2c.o
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@ -0,0 +1,346 @@
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/*
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* (C) Copyright 2015, Samsung Electronics
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* Przemyslaw Marczak <p.marczak@samsung.com>
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*
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* This file is based on: drivers/i2c/soft-i2c.c,
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* with added driver-model support and code cleanup.
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*/
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#include <common.h>
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#include <errno.h>
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#include <dm.h>
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#include <i2c.h>
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#include <asm/gpio.h>
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#define DEFAULT_UDELAY 5
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#define RETRIES 0
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#define I2C_ACK 0
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#define I2C_NOACK 1
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DECLARE_GLOBAL_DATA_PTR;
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enum {
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PIN_SDA = 0,
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PIN_SCL,
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PIN_COUNT,
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};
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struct i2c_gpio_bus {
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/**
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* udelay - delay [us] between GPIO toggle operations,
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* which is 1/4 of I2C speed clock period.
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*/
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int udelay;
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/* sda, scl */
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struct gpio_desc gpios[PIN_COUNT];
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};
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static int i2c_gpio_sda_get(struct gpio_desc *sda)
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{
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return dm_gpio_get_value(sda);
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}
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static void i2c_gpio_sda_set(struct gpio_desc *sda, int bit)
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{
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if (bit) {
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dm_gpio_set_dir_flags(sda, GPIOD_IS_IN);
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} else {
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dm_gpio_set_dir_flags(sda, GPIOD_IS_OUT);
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dm_gpio_set_value(sda, 0);
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}
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}
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static void i2c_gpio_scl_set(struct gpio_desc *scl, int bit)
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{
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dm_gpio_set_dir_flags(scl, GPIOD_IS_OUT);
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dm_gpio_set_value(scl, bit);
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}
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static void i2c_gpio_write_bit(struct gpio_desc *scl, struct gpio_desc *sda,
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int delay, uchar bit)
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{
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i2c_gpio_scl_set(scl, 0);
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udelay(delay);
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i2c_gpio_sda_set(sda, bit);
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udelay(delay);
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i2c_gpio_scl_set(scl, 1);
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udelay(2 * delay);
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}
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static int i2c_gpio_read_bit(struct gpio_desc *scl, struct gpio_desc *sda,
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int delay)
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{
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int value;
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i2c_gpio_scl_set(scl, 1);
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udelay(delay);
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value = i2c_gpio_sda_get(sda);
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udelay(delay);
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i2c_gpio_scl_set(scl, 0);
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udelay(2 * delay);
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return value;
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}
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/* START: High -> Low on SDA while SCL is High */
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static void i2c_gpio_send_start(struct gpio_desc *scl, struct gpio_desc *sda,
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int delay)
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{
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udelay(delay);
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i2c_gpio_sda_set(sda, 1);
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udelay(delay);
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i2c_gpio_scl_set(scl, 1);
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udelay(delay);
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i2c_gpio_sda_set(sda, 0);
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udelay(delay);
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}
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/* STOP: Low -> High on SDA while SCL is High */
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static void i2c_gpio_send_stop(struct gpio_desc *scl, struct gpio_desc *sda,
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int delay)
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{
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i2c_gpio_scl_set(scl, 0);
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udelay(delay);
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i2c_gpio_sda_set(sda, 0);
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udelay(delay);
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i2c_gpio_scl_set(scl, 1);
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udelay(delay);
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i2c_gpio_sda_set(sda, 1);
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udelay(delay);
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}
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/* ack should be I2C_ACK or I2C_NOACK */
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static void i2c_gpio_send_ack(struct gpio_desc *scl, struct gpio_desc *sda,
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int delay, int ack)
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{
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i2c_gpio_write_bit(scl, sda, delay, ack);
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i2c_gpio_scl_set(scl, 0);
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udelay(delay);
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}
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/**
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* Send a reset sequence consisting of 9 clocks with the data signal high
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* to clock any confused device back into an idle state. Also send a
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* <stop> at the end of the sequence for belts & suspenders.
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*/
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static void i2c_gpio_send_reset(struct gpio_desc *scl, struct gpio_desc *sda,
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int delay)
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{
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int j;
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for (j = 0; j < 9; j++)
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i2c_gpio_write_bit(scl, sda, delay, 1);
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i2c_gpio_send_stop(scl, sda, delay);
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}
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/* Set sda high with low clock, before reading slave data */
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static void i2c_gpio_sda_high(struct gpio_desc *scl, struct gpio_desc *sda,
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int delay)
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{
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i2c_gpio_scl_set(scl, 0);
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udelay(delay);
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i2c_gpio_sda_set(sda, 1);
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udelay(delay);
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}
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/* Send 8 bits and look for an acknowledgement */
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static int i2c_gpio_write_byte(struct gpio_desc *scl, struct gpio_desc *sda,
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int delay, uchar data)
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{
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int j;
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int nack;
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for (j = 0; j < 8; j++) {
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i2c_gpio_write_bit(scl, sda, delay, data & 0x80);
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data <<= 1;
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}
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udelay(delay);
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/* Look for an <ACK>(negative logic) and return it */
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i2c_gpio_sda_high(scl, sda, delay);
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nack = i2c_gpio_read_bit(scl, sda, delay);
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return nack; /* not a nack is an ack */
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}
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/**
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* if ack == I2C_ACK, ACK the byte so can continue reading, else
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* send I2C_NOACK to end the read.
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*/
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static uchar i2c_gpio_read_byte(struct gpio_desc *scl, struct gpio_desc *sda,
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int delay, int ack)
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{
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int data;
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int j;
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i2c_gpio_sda_high(scl, sda, delay);
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data = 0;
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for (j = 0; j < 8; j++) {
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data <<= 1;
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data |= i2c_gpio_read_bit(scl, sda, delay);
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}
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i2c_gpio_send_ack(scl, sda, delay, ack);
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return data;
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}
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/* send start and the slave chip address */
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int i2c_send_slave_addr(struct gpio_desc *scl, struct gpio_desc *sda, int delay,
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uchar chip)
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{
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i2c_gpio_send_start(scl, sda, delay);
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if (i2c_gpio_write_byte(scl, sda, delay, chip)) {
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i2c_gpio_send_stop(scl, sda, delay);
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return -EIO;
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}
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return 0;
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}
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static int i2c_gpio_write_data(struct i2c_gpio_bus *bus, uchar chip,
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uchar *buffer, int len,
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bool end_with_repeated_start)
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{
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struct gpio_desc *scl = &bus->gpios[PIN_SCL];
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struct gpio_desc *sda = &bus->gpios[PIN_SDA];
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unsigned int delay = bus->udelay;
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int failures = 0;
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debug("%s: chip %x buffer %p len %d\n", __func__, chip, buffer, len);
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if (i2c_send_slave_addr(scl, sda, delay, chip << 1)) {
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debug("i2c_write, no chip responded %02X\n", chip);
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return -EIO;
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}
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while (len-- > 0) {
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if (i2c_gpio_write_byte(scl, sda, delay, *buffer++))
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failures++;
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}
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if (!end_with_repeated_start) {
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i2c_gpio_send_stop(scl, sda, delay);
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return failures;
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}
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if (i2c_send_slave_addr(scl, sda, delay, (chip << 1) | 0x1)) {
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debug("i2c_write, no chip responded %02X\n", chip);
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return -EIO;
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}
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return failures;
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}
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static int i2c_gpio_read_data(struct i2c_gpio_bus *bus, uchar chip,
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uchar *buffer, int len)
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{
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struct gpio_desc *scl = &bus->gpios[PIN_SCL];
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struct gpio_desc *sda = &bus->gpios[PIN_SDA];
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unsigned int delay = bus->udelay;
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debug("%s: chip %x buffer: %p len %d\n", __func__, chip, buffer, len);
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while (len-- > 0)
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*buffer++ = i2c_gpio_read_byte(scl, sda, delay, len == 0);
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i2c_gpio_send_stop(scl, sda, delay);
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return 0;
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}
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static int i2c_gpio_xfer(struct udevice *dev, struct i2c_msg *msg, int nmsgs)
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{
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struct i2c_gpio_bus *bus = dev_get_priv(dev);
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int ret;
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for (; nmsgs > 0; nmsgs--, msg++) {
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bool next_is_read = nmsgs > 1 && (msg[1].flags & I2C_M_RD);
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if (msg->flags & I2C_M_RD) {
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ret = i2c_gpio_read_data(bus, msg->addr, msg->buf,
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msg->len);
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} else {
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ret = i2c_gpio_write_data(bus, msg->addr, msg->buf,
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msg->len, next_is_read);
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}
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if (ret)
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return -EREMOTEIO;
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}
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return 0;
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}
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static int i2c_gpio_probe(struct udevice *dev, uint chip, uint chip_flags)
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{
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struct i2c_gpio_bus *bus = dev_get_priv(dev);
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struct gpio_desc *scl = &bus->gpios[PIN_SCL];
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struct gpio_desc *sda = &bus->gpios[PIN_SDA];
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unsigned int delay = bus->udelay;
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int ret;
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i2c_gpio_send_start(scl, sda, delay);
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ret = i2c_gpio_write_byte(scl, sda, delay, (chip << 1) | 0);
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i2c_gpio_send_stop(scl, sda, delay);
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debug("%s: bus: %d (%s) chip: %x flags: %x ret: %d\n",
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__func__, dev->seq, dev->name, chip, chip_flags, ret);
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return ret;
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}
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static int i2c_gpio_set_bus_speed(struct udevice *dev, unsigned int speed_hz)
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{
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struct i2c_gpio_bus *bus = dev_get_priv(dev);
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struct gpio_desc *scl = &bus->gpios[PIN_SCL];
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struct gpio_desc *sda = &bus->gpios[PIN_SDA];
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bus->udelay = 1000000 / (speed_hz << 2);
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i2c_gpio_send_reset(scl, sda, bus->udelay);
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return 0;
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}
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static int i2c_gpio_ofdata_to_platdata(struct udevice *dev)
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{
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struct i2c_gpio_bus *bus = dev_get_priv(dev);
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const void *blob = gd->fdt_blob;
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int node = dev->of_offset;
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int ret;
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ret = gpio_request_list_by_name(dev, "gpios", bus->gpios,
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ARRAY_SIZE(bus->gpios), 0);
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if (ret < 0)
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goto error;
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bus->udelay = fdtdec_get_int(blob, node, "i2c-gpio,delay-us",
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DEFAULT_UDELAY);
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return 0;
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error:
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error("Can't get %s gpios! Error: %d", dev->name, ret);
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return ret;
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}
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static const struct dm_i2c_ops i2c_gpio_ops = {
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.xfer = i2c_gpio_xfer,
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.probe_chip = i2c_gpio_probe,
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.set_bus_speed = i2c_gpio_set_bus_speed,
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};
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static const struct udevice_id i2c_gpio_ids[] = {
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{ .compatible = "i2c-gpio" },
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{ }
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};
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U_BOOT_DRIVER(i2c_gpio) = {
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.name = "i2c-gpio",
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.id = UCLASS_I2C,
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.of_match = i2c_gpio_ids,
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.ofdata_to_platdata = i2c_gpio_ofdata_to_platdata,
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.priv_auto_alloc_size = sizeof(struct i2c_gpio_bus),
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.ops = &i2c_gpio_ops,
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};
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