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>master
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705fcf4de4
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c54473cb25
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I2C gpio device binding |
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======================= |
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|
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Driver: |
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- drivers/i2c/i2c-gpio.c |
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|
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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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}; |
@ -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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