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/*
* i2c-algo-busclear: Bus clear logic implementation based on GPIO
*
* Copyright (c) 2013, NVIDIA Corporation.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/gpio.h>
#include <linux/export.h>
/*I2C controller supports eight-byte burst transfer*/
#define RETRY_MAX_COUNT (9 * 8 + 1)
int i2c_algo_busclear_gpio(struct device *dev, int scl_gpio, int scl_gpio_flags,
int sda_gpio, int sda_gpio_flags,
int max_retry_clock, int clock_speed_hz)
{
int ret;
int retry_clk = min(max_retry_clock, RETRY_MAX_COUNT);
int recovered_successfully = 0;
int val;
int clk_delay = DIV_ROUND_UP(1000000, 2 * clock_speed_hz);
int clk_count = 0;
if ((!gpio_is_valid(scl_gpio)) || !gpio_is_valid((sda_gpio))) {
dev_err(dev, "GPIOs are not valid\n");
return -EINVAL;
}
ret = gpio_request_one(scl_gpio,
scl_gpio_flags | GPIOF_OUT_INIT_HIGH, "scl_gpio");
if (ret < 0) {
dev_err(dev, "GPIO request for scl_gpio failed, err = %d\n",
ret);
return ret;
}
ret = gpio_request_one(sda_gpio,
sda_gpio_flags | GPIOF_IN, "sda_gpio");
if (ret < 0) {
dev_err(dev, "GPIO request for sda_gpio failed, err = %d\n",
ret);
gpio_free(scl_gpio);
return ret;
}
gpio_direction_input(sda_gpio);
while (retry_clk--) {
clk_count++;
gpio_direction_output(scl_gpio, 0);
udelay(clk_delay);
gpio_direction_output(scl_gpio, 1);
udelay(clk_delay);
/* check whether sda struct low release */
val = gpio_get_value(sda_gpio);
if (val) {
/* send START */
gpio_direction_output(sda_gpio, 0);
udelay(clk_delay);
/* send STOP in next clock cycle */
gpio_direction_output(scl_gpio, 0);
udelay(clk_delay);
gpio_direction_output(scl_gpio, 1);
udelay(clk_delay);
gpio_direction_output(sda_gpio, 1);
udelay(clk_delay);
recovered_successfully = 1;
break;
}
}
gpio_free(scl_gpio);
gpio_free(sda_gpio);
if (!recovered_successfully) {
dev_err(dev, "arb lost recovered failed with total clk %d\n",
clk_count);
return -EINVAL;
}
dev_err(dev, "arb lost recovered in clock count %d\n", clk_count);
return 0;
}
EXPORT_SYMBOL_GPL(i2c_algo_busclear_gpio);
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