[PATCH 3/4] i2c: add i2c-gpio support
Jean-Christophe PLAGNIOL-VILLARD
plagnioj at jcrosoft.com
Fri Nov 2 05:36:51 EDT 2012
Based on linux 3.7-rc2
Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj at jcrosoft.com>
---
drivers/i2c/busses/Kconfig | 8 ++
drivers/i2c/busses/Makefile | 1 +
drivers/i2c/busses/i2c-gpio.c | 177 +++++++++++++++++++++++++++++++++++++++++
include/i2c/i2c-gpio.h | 38 +++++++++
4 files changed, 224 insertions(+)
create mode 100644 drivers/i2c/busses/i2c-gpio.c
create mode 100644 include/i2c/i2c-gpio.h
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 3f998ea..17e33cb 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -4,6 +4,14 @@
menu "I2C Hardware Bus support"
+config I2C_GPIO
+ tristate "GPIO-based bitbanging I2C"
+ depends on GENERIC_GPIO
+ select I2C_ALGOBIT
+ help
+ This is a very simple bitbanging I2C driver utilizing the
+ arch-neutral GPIO API to control the SCL and SDA lines.
+
config I2C_IMX
bool "MPC85xx/i.MX I2C Master driver"
depends on (ARCH_IMX && !ARCH_IMX1) || ARCH_MPC85XX
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index e4c5125..18c7c46 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -1,2 +1,3 @@
+obj-$(CONFIG_I2C_GPIO) += i2c-gpio.o
obj-$(CONFIG_I2C_IMX) += i2c-imx.o
obj-$(CONFIG_I2C_OMAP) += i2c-omap.o
diff --git a/drivers/i2c/busses/i2c-gpio.c b/drivers/i2c/busses/i2c-gpio.c
new file mode 100644
index 0000000..98ce2d5
--- /dev/null
+++ b/drivers/i2c/busses/i2c-gpio.c
@@ -0,0 +1,177 @@
+/*
+ * Bitbanging I2C bus driver using the GPIO API
+ *
+ * Copyright (C) 2007 Atmel Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <common.h>
+#include <driver.h>
+#include <i2c/i2c.h>
+#include <i2c/i2c-algo-bit.h>
+#include <i2c/i2c-gpio.h>
+#include <init.h>
+#include <gpio.h>
+
+struct i2c_gpio_private_data {
+ struct i2c_adapter adap;
+ struct i2c_algo_bit_data bit_data;
+ struct i2c_gpio_platform_data pdata;
+};
+
+/* Toggle SDA by changing the direction of the pin */
+static void i2c_gpio_setsda_dir(void *data, int state)
+{
+ struct i2c_gpio_platform_data *pdata = data;
+
+ if (state)
+ gpio_direction_input(pdata->sda_pin);
+ else
+ gpio_direction_output(pdata->sda_pin, 0);
+}
+
+/*
+ * Toggle SDA by changing the output value of the pin. This is only
+ * valid for pins configured as open drain (i.e. setting the value
+ * high effectively turns off the output driver.)
+ */
+static void i2c_gpio_setsda_val(void *data, int state)
+{
+ struct i2c_gpio_platform_data *pdata = data;
+
+ gpio_set_value(pdata->sda_pin, state);
+}
+
+/* Toggle SCL by changing the direction of the pin. */
+static void i2c_gpio_setscl_dir(void *data, int state)
+{
+ struct i2c_gpio_platform_data *pdata = data;
+
+ if (state)
+ gpio_direction_input(pdata->scl_pin);
+ else
+ gpio_direction_output(pdata->scl_pin, 0);
+}
+
+/*
+ * Toggle SCL by changing the output value of the pin. This is used
+ * for pins that are configured as open drain and for output-only
+ * pins. The latter case will break the i2c protocol, but it will
+ * often work in practice.
+ */
+static void i2c_gpio_setscl_val(void *data, int state)
+{
+ struct i2c_gpio_platform_data *pdata = data;
+
+ gpio_set_value(pdata->scl_pin, state);
+}
+
+static int i2c_gpio_getsda(void *data)
+{
+ struct i2c_gpio_platform_data *pdata = data;
+
+ return gpio_get_value(pdata->sda_pin);
+}
+
+static int i2c_gpio_getscl(void *data)
+{
+ struct i2c_gpio_platform_data *pdata = data;
+
+ return gpio_get_value(pdata->scl_pin);
+}
+
+static int i2c_gpio_probe(struct device_d *dev)
+{
+ struct i2c_gpio_private_data *priv;
+ struct i2c_gpio_platform_data *pdata;
+ struct i2c_algo_bit_data *bit_data;
+ struct i2c_adapter *adap;
+ int ret;
+
+ priv = xzalloc(sizeof(*priv));
+
+ adap = &priv->adap;
+ bit_data = &priv->bit_data;
+ pdata = &priv->pdata;
+
+ if (!dev->platform_data)
+ return -ENXIO;
+ memcpy(pdata, dev->platform_data, sizeof(*pdata));
+
+ ret = gpio_request(pdata->sda_pin, "sda");
+ if (ret)
+ goto err_request_sda;
+ ret = gpio_request(pdata->scl_pin, "scl");
+ if (ret)
+ goto err_request_scl;
+
+ if (pdata->sda_is_open_drain) {
+ gpio_direction_output(pdata->sda_pin, 1);
+ bit_data->setsda = i2c_gpio_setsda_val;
+ } else {
+ gpio_direction_input(pdata->sda_pin);
+ bit_data->setsda = i2c_gpio_setsda_dir;
+ }
+
+ if (pdata->scl_is_open_drain || pdata->scl_is_output_only) {
+ gpio_direction_output(pdata->scl_pin, 1);
+ bit_data->setscl = i2c_gpio_setscl_val;
+ } else {
+ gpio_direction_input(pdata->scl_pin);
+ bit_data->setscl = i2c_gpio_setscl_dir;
+ }
+
+ if (!pdata->scl_is_output_only)
+ bit_data->getscl = i2c_gpio_getscl;
+ bit_data->getsda = i2c_gpio_getsda;
+
+ if (pdata->udelay)
+ bit_data->udelay = pdata->udelay;
+ else if (pdata->scl_is_output_only)
+ bit_data->udelay = 50; /* 10 kHz */
+ else
+ bit_data->udelay = 5; /* 100 kHz */
+
+ if (pdata->timeout_ms)
+ bit_data->timeout_ms = pdata->timeout_ms;
+ else
+ bit_data->timeout_ms = 100; /* 100 ms */
+
+ bit_data->data = pdata;
+
+ adap->algo_data = bit_data;
+ adap->dev.parent = dev;
+
+ adap->nr = dev->id;
+ ret = i2c_bit_add_numbered_bus(adap);
+ if (ret)
+ goto err_add_bus;
+
+ dev_info(dev, "using pins %u (SDA) and %u (SCL%s)\n",
+ pdata->sda_pin, pdata->scl_pin,
+ pdata->scl_is_output_only
+ ? ", no clock stretching" : "");
+
+ return 0;
+
+err_add_bus:
+ gpio_free(pdata->scl_pin);
+err_request_scl:
+ gpio_free(pdata->sda_pin);
+err_request_sda:
+ return ret;
+}
+
+static struct driver_d i2c_gpio_driver = {
+ .name = "i2c-gpio",
+ .probe = i2c_gpio_probe,
+};
+
+static int __init i2c_gpio_init(void)
+{
+ return platform_driver_register(&i2c_gpio_driver);
+}
+device_initcall(i2c_gpio_init);
diff --git a/include/i2c/i2c-gpio.h b/include/i2c/i2c-gpio.h
new file mode 100644
index 0000000..55feb82
--- /dev/null
+++ b/include/i2c/i2c-gpio.h
@@ -0,0 +1,38 @@
+/*
+ * i2c-gpio interface to platform code
+ *
+ * Copyright (C) 2007 Atmel Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#ifndef _LINUX_I2C_GPIO_H
+#define _LINUX_I2C_GPIO_H
+
+/**
+ * struct i2c_gpio_platform_data - Platform-dependent data for i2c-gpio
+ * @sda_pin: GPIO pin ID to use for SDA
+ * @scl_pin: GPIO pin ID to use for SCL
+ * @udelay: signal toggle delay. SCL frequency is (500 / udelay) kHz
+ * @timeout_ms: clock stretching timeout in ms. If the slave keeps
+ * SCL low for longer than this, the transfer will time out.
+ * @sda_is_open_drain: SDA is configured as open drain, i.e. the pin
+ * isn't actively driven high when setting the output value high.
+ * gpio_get_value() must return the actual pin state even if the
+ * pin is configured as an output.
+ * @scl_is_open_drain: SCL is set up as open drain. Same requirements
+ * as for sda_is_open_drain apply.
+ * @scl_is_output_only: SCL output drivers cannot be turned off.
+ */
+struct i2c_gpio_platform_data {
+ unsigned int sda_pin;
+ unsigned int scl_pin;
+ int udelay;
+ int timeout_ms;
+ unsigned int sda_is_open_drain:1;
+ unsigned int scl_is_open_drain:1;
+ unsigned int scl_is_output_only:1;
+};
+
+#endif /* _LINUX_I2C_GPIO_H */
--
1.7.10.4
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