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Message-Id: <11735324081261-git-send-email-hskinnemoen@atmel.com>
Date: Sat, 10 Mar 2007 14:13:28 +0100
From: Haavard Skinnemoen <hskinnemoen@...el.com>
To: David Brownell <david-b@...bell.net>
Cc: Jean Delvare <khali@...ux-fr.org>, Bryan Wu <bryan.wu@...log.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Deepak Saxena <dsaxena@...xity.net>,
linux-kernel@...r.kernel.org,
Haavard Skinnemoen <hskinnemoen@...el.com>
Subject: [PATCH v2] Bitbanging i2c bus driver using the GPIO API
This is a very simple bitbanging i2c bus driver utilizing the new
arch-neutral GPIO API. Useful for chips that don't have a built-in
i2c controller, additional i2c busses, or testing purposes.
To use, include something similar to the following in the
board-specific setup code:
#include <linux/i2c-gpio.h>
static struct i2c_gpio_platform_data i2c_gpio_data = {
.sda_pin = GPIO_PIN_FOO,
.scl_pin = GPIO_PIN_BAR,
};
static struct platform_device i2c_gpio_device = {
.name = "i2c-gpio",
.id = 0,
.dev = {
.platform_data = &i2c_gpio_data,
},
};
Register this platform_device, set up the i2c pins as GPIO if
required and you're ready to go.
Signed-off-by: Haavard Skinnemoen <hskinnemoen@...el.com>
---
This patch is different from the first patch in the following ways:
* Handles pins set up as open drain (aka multidrive) by toggling
the output value instead of the direction
* Handles output-only SCL pins the same way, and also does not
install a getscl() callback for such pins
* Does not add anything to include/linux/i2c-ids.h
* Sets the output value explicitly after changing the direction to
output.
* Plugs a memory leak in remove() -- algo_data wasn't freed.
* Prints out the pin IDs in decimal, with an extra note when clock
stretching isn't supported
This version has been compile-tested only. I'll give it a spin when I
get back to work on monday.
Dave, does this address your concerns?
Haavard
drivers/i2c/busses/Kconfig | 8 ++
drivers/i2c/busses/Makefile | 1 +
drivers/i2c/busses/i2c-gpio.c | 211 +++++++++++++++++++++++++++++++++++++++++
include/linux/i2c-gpio.h | 30 ++++++
4 files changed, 250 insertions(+), 0 deletions(-)
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index fb19dbb..52f79d1 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -102,6 +102,14 @@ config I2C_ELEKTOR
This support is also available as a module. If so, the module
will be called i2c-elektor.
+config I2C_GPIO
+ tristate "GPIO-based bitbanging i2c driver"
+ depends on I2C && 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_HYDRA
tristate "CHRP Apple Hydra Mac I/O I2C interface"
depends on I2C && PCI && PPC_CHRP && EXPERIMENTAL
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 290b540..68f2b05 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -11,6 +11,7 @@ obj-$(CONFIG_I2C_AMD8111) += i2c-amd8111.o
obj-$(CONFIG_I2C_AT91) += i2c-at91.o
obj-$(CONFIG_I2C_AU1550) += i2c-au1550.o
obj-$(CONFIG_I2C_ELEKTOR) += i2c-elektor.o
+obj-$(CONFIG_I2C_GPIO) += i2c-gpio.o
obj-$(CONFIG_I2C_HYDRA) += i2c-hydra.o
obj-$(CONFIG_I2C_I801) += i2c-i801.o
obj-$(CONFIG_I2C_I810) += i2c-i810.o
diff --git a/drivers/i2c/busses/i2c-gpio.c b/drivers/i2c/busses/i2c-gpio.c
new file mode 100644
index 0000000..423db0a
--- /dev/null
+++ b/drivers/i2c/busses/i2c-gpio.c
@@ -0,0 +1,211 @@
+/*
+ * Bitbanging i2c bus driver using the GPIO API
+ *
+ * Copyright (C) 2006 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 <linux/i2c.h>
+#include <linux/i2c-algo-bit.h>
+#include <linux/i2c-gpio.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+#include <asm/gpio.h>
+
+/* 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);
+ gpio_set_value(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);
+ gpio_set_value(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);
+}
+
+int i2c_gpio_getsda(void *data)
+{
+ struct i2c_gpio_platform_data *pdata = data;
+
+ return gpio_get_value(pdata->sda_pin);
+}
+
+int i2c_gpio_getscl(void *data)
+{
+ struct i2c_gpio_platform_data *pdata = data;
+
+ return gpio_get_value(pdata->scl_pin);
+}
+
+static int __init i2c_gpio_probe(struct platform_device *pdev)
+{
+ struct i2c_gpio_platform_data *pdata;
+ struct i2c_algo_bit_data *bit_data;
+ struct i2c_adapter *adap;
+ int ret;
+
+ pdata = pdev->dev.platform_data;
+ if (!pdata)
+ return -ENXIO;
+
+ ret = -ENOMEM;
+ adap = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL);
+ if (!adap)
+ goto err_alloc_adap;
+ bit_data = kzalloc(sizeof(struct i2c_algo_bit_data), GFP_KERNEL);
+ if (!bit_data)
+ goto err_alloc_bit_data;
+
+ 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);
+ gpio_set_value(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);
+ gpio_set_value(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,
+ bit_data->udelay = 5, /* 100 kHz */
+ bit_data->timeout = HZ / 10, /* 100 ms */
+ bit_data->data = pdata;
+
+ adap->owner = THIS_MODULE;
+ snprintf(adap->name, I2C_NAME_SIZE, "i2c-gpio%d", pdev->id);
+ adap->algo_data = bit_data;
+ adap->dev.parent = &pdev->dev;
+
+ ret = i2c_bit_add_bus(adap);
+ if (ret)
+ goto err_add_bus;
+
+ platform_set_drvdata(pdev, adap);
+
+ dev_info(&pdev->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:
+ kfree(bit_data);
+err_alloc_bit_data:
+ kfree(adap);
+err_alloc_adap:
+ return ret;
+}
+
+static int __exit i2c_gpio_remove(struct platform_device *pdev)
+{
+ struct i2c_gpio_platform_data *pdata;
+ struct i2c_adapter *adap;
+
+ adap = platform_get_drvdata(pdev);
+ pdata = pdev->dev.platform_data;
+
+ i2c_del_adapter(adap);
+ gpio_free(pdata->scl_pin);
+ gpio_free(pdata->sda_pin);
+ kfree(adap->algo_data);
+ kfree(adap);
+
+ return 0;
+}
+
+static struct platform_driver i2c_gpio_driver = {
+ .driver = {
+ .name = "i2c-gpio",
+ .owner = THIS_MODULE,
+ },
+ .remove = __exit_p(i2c_gpio_remove),
+};
+
+static int __init i2c_gpio_init(void)
+{
+ int ret;
+
+ ret = platform_driver_probe(&i2c_gpio_driver, i2c_gpio_probe);
+ if (ret)
+ printk("i2c-gpio: probe failed: %d\n", ret);
+
+ return ret;
+}
+module_init(i2c_gpio_init);
+
+static void __exit i2c_gpio_exit(void)
+{
+ platform_driver_unregister(&i2c_gpio_driver);
+}
+module_exit(i2c_gpio_exit);
+
+MODULE_AUTHOR("Haavard Skinnemoen <hskinnemoen@...el.com>");
+MODULE_DESCRIPTION("Platform-independent bitbanging i2c driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/i2c-gpio.h b/include/linux/i2c-gpio.h
new file mode 100644
index 0000000..1e8fa29
--- /dev/null
+++ b/include/linux/i2c-gpio.h
@@ -0,0 +1,30 @@
+/*
+ * 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
+ * @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.
+ * @scl_is_open_drain: SCL is set up as open drain.
+ * @scl_is_output_only: SCL output drivers cannot be turned off.
+ */
+struct i2c_gpio_platform_data {
+ unsigned int sda_pin;
+ unsigned int scl_pin;
+ 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 */
--
1.4.4.4
-
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