Add an i2c bus driver providing virtual i2c busses using a hardware MUX
sitting on a master bus and controlled through gpio pins.
E.G. something like:
---------- ---------- Virtual bus 1 - - - - -
| | SCL/SDA | |-------------- | |
| |------------| |
| | | | Virtual bus 2 | |
| Linux | GPIO 1..N | MUX |--------------- Devices
| |------------| | | |
| | | | Virtual bus M
| | | |---------------| |
---------- ---------- - - - - -
SCL/SDA of the master I2C bus is multiplexed to virtual bus 1..M
according to the settings of the GPIO pins 1..N.
Signed-off-by: Peter Korsgaard <peter.korsgaard@xxxxxxxxx>
---
Documentation/i2c/busses/i2c-gpiomux | 65 +++++++++++
MAINTAINERS | 7 ++
drivers/i2c/busses/Kconfig | 12 ++
drivers/i2c/busses/Makefile | 1 +
drivers/i2c/busses/i2c-gpiomux.c | 196 ++++++++++++++++++++++++++++++++++
include/linux/i2c-gpiomux.h | 35 ++++++
6 files changed, 316 insertions(+), 0 deletions(-)
create mode 100644 Documentation/i2c/busses/i2c-gpiomux
create mode 100644 drivers/i2c/busses/i2c-gpiomux.c
create mode 100644 include/linux/i2c-gpiomux.h
diff --git a/Documentation/i2c/busses/i2c-gpiomux b/Documentation/i2c/busses/i2c-gpiomux
new file mode 100644
index 0000000..b0a7746
--- /dev/null
+++ b/Documentation/i2c/busses/i2c-gpiomux
@@ -0,0 +1,65 @@
+Kernel driver i2c-gpiomux
+
+Author: Peter Korsgaard <peter.korsgaard@xxxxxxxxx>
+
+Description
+-----------
+
+i2c-gpiomux is an i2c bus driver providing virtual I2C busses from a
+master I2C bus and a hardware MUX controlled through GPIO pins.
+
+E.G.:
+
+ ---------- ---------- Virtual bus 1 - - - - -
+ | | SCL/SDA | |-------------- | |
+ | |------------| |
+ | | | | Virtual bus 2 | |
+ | Linux | GPIO 1..N | MUX |--------------- Devices
+ | |------------| | | |
+ | | | | Virtual bus M
+ | | | |---------------| |
+ ---------- ---------- - - - - -
+
+SCL/SDA of the master I2C bus is multiplexed to virtual bus 1..M
+according to the settings of the GPIO pins 1..N.
+
+Usage
+-----
+
+i2c-gpiomux uses the platform bus, so you need to provide a struct
+platform_device with the platform_data pointing to a struct
+gpiomux_i2c_platform_data with the I2C adapter number of the master
+bus, the number of virtual busses to create and the GPIO pins used
+to control it. See include/linux/i2c-gpiomux.h for details.
+
+E.G. something like this for a MUX providing 4 virtual busses
+controlled through 3 GPIO pins:
+
+#include <linux/i2c-gpiomux.h>
+#include <linux/platform_device.h>
+
+static unsigned myboard_gpiomux_pins[] = {
+ AT91_PIN_PC26, AT91_PIN_PC25, AT91_PIN_PC24
+};
+
+static unsigned myboard_gpiomux_values[] = {
+ 0, 1, 2, 3
+};
+
+static struct gpiomux_i2c_platform_data myboard_i2cmux_data = {
+ .parent = 1,
+ .base_nr = 2,
+ .busses = ARRAY_SIZE(myboard_gpiomux_values),
+ .gpios = ARRAY_SIZE(myboard_gpiomux_pins),
+ .gpio = myboard_gpiomux_pins,
+ .values = myboard_gpiomux_values,
+ .idle = 4,
+};
+
+static struct platform_device myboard_i2cmux = {
+ .name = "i2c-gpiomux",
+ .id = 0,
+ .dev = {
+ .platform_data = &myboard_i2cmux_data,
+ },
+};
diff --git a/MAINTAINERS b/MAINTAINERS
index 7642365..f80ad93 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2453,6 +2453,13 @@ S: Supported
F: drivers/i2c/busses/i2c-gpio.c
F: include/linux/i2c-gpio.h
+GENERIC GPIO I2C MULTIPLEXER DRIVER
+M: Peter Korsgaard <peter.korsgaard@xxxxxxxxx>
+L: linux-i2c@xxxxxxxxxxxxxxx
+S: Supported
+F: drivers/i2c/busses/i2c-gpiomux.c
+F: include/linux/i2c-gpiomux.h
+
GENERIC HDLC (WAN) DRIVERS
M: Krzysztof Halasa <khc@xxxxxxxxx>
W: http://www.kernel.org/pub/linux/utils/net/hdlc/
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index bceafbf..055b0f1 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -364,6 +364,18 @@ config I2C_GPIO
This is a very simple bitbanging I2C driver utilizing the
arch-neutral GPIO API to control the SCL and SDA lines.
+config I2C_GPIOMUX
+ tristate "GPIO-based I2C multiplexer"
+ depends on GENERIC_GPIO
+ help
+ If you say yes to this option, support will be included for a
+ GPIO based I2C multiplexer. This driver provides virtual I2C
+ busses from a master bus through a MUX controlled through
+ the generic GPIO interface.
+
+ This driver can also be built as a module. If so, the module
+ will be called i2c-gpiomux.
+
config I2C_HIGHLANDER
tristate "Highlander FPGA SMBus interface"
depends on SH_HIGHLANDER
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 936880b..5ec15ec 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -35,6 +35,7 @@ obj-$(CONFIG_I2C_CPM) += i2c-cpm.o
obj-$(CONFIG_I2C_DAVINCI) += i2c-davinci.o
obj-$(CONFIG_I2C_DESIGNWARE) += i2c-designware.o
obj-$(CONFIG_I2C_GPIO) += i2c-gpio.o
+obj-$(CONFIG_I2C_GPIOMUX) += i2c-gpiomux.o
obj-$(CONFIG_I2C_HIGHLANDER) += i2c-highlander.o
obj-$(CONFIG_I2C_IBM_IIC) += i2c-ibm_iic.o
obj-$(CONFIG_I2C_IMX) += i2c-imx.o
diff --git a/drivers/i2c/busses/i2c-gpiomux.c b/drivers/i2c/busses/i2c-gpiomux.c
new file mode 100644
index 0000000..b4cc9e2
--- /dev/null
+++ b/drivers/i2c/busses/i2c-gpiomux.c
@@ -0,0 +1,196 @@
+/*
+ * I2C multiplexer using GPIO API
+ *
+ * Peter Korsgaard <peter.korsgaard@xxxxxxxxx>
+ *
+ * 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-gpiomux.h>
+#include <linux/platform_device.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/gpio.h>
+
+struct gpiomux_i2c {
+ struct i2c_adapter *parent; /* parent bus */
+ struct i2c_adapter *adap; /* children busses */
+ struct gpiomux_i2c_platform_data data;
+};
+
+static void gpiomux_set(struct gpiomux_i2c *i2c, unsigned val)
+{
+ int i;
+
+ for (i = 0; i < i2c->data.gpios; i++)
+ gpio_set_value(i2c->data.gpio[i], val & (1<<i));
+}
+
+static int gpiomux_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
+ int num)
+{
+ struct gpiomux_i2c *i2c = i2c_get_adapdata(adap);
+ int nr = adap->nr - i2c->data.base_nr;
+ int ret;
+
+ rt_mutex_lock(&i2c->parent->bus_lock);
+
+ gpiomux_set(i2c, i2c->data.values[nr]);
+ ret = i2c->parent->algo->master_xfer(i2c->parent, msgs, num);
+ gpiomux_set(i2c, i2c->data.idle);
+
+ rt_mutex_unlock(&i2c->parent->bus_lock);
+
+ return ret;
+}
+
+static u32 gpiomux_func(struct i2c_adapter *adap)
+{
+ struct gpiomux_i2c *i2c = i2c_get_adapdata(adap);
+
+ return i2c->parent->algo->functionality(i2c->parent);
+}
+
+static struct i2c_algorithm gpiomux_algorithm = {
+ .master_xfer = gpiomux_xfer,
+ .functionality = gpiomux_func,
+};
+
+static struct i2c_adapter gpiomux_adapter = {
+ .owner = THIS_MODULE,
+ .name = "gpiomux",
+ .class = I2C_CLASS_HWMON,
+ .algo = &gpiomux_algorithm,
+ .timeout = 2,
+ .retries = 1
+};
+
+static int __devinit gpiomux_probe(struct platform_device *pdev)
+{
+ struct gpiomux_i2c *i2c;
+ struct gpiomux_i2c_platform_data *pdata;
+ struct i2c_adapter *adap;
+ int i, j, ret;
+
+ pdata = pdev->dev.platform_data;
+ if (!pdata) {
+ dev_err(&pdev->dev, "Missing platform data\n");
+ return -ENODEV;
+ }
+
+ adap = i2c_get_adapter(pdata->parent);
+ if (!adap) {
+ dev_err(&pdev->dev, "Parent adapter (%d) not found\n",
+ pdata->parent);
+ return -ENODEV;
+ }
+
+ i2c = kzalloc(sizeof(*i2c), GFP_KERNEL);
+ if (!i2c) {
+ ret = -ENOMEM;
+ goto alloc_failed;
+ }
+
+ i2c->parent = adap;
+ i2c->data = *pdata;
+ i2c->adap = kzalloc(sizeof(struct i2c_adapter)*pdata->busses,
+ GFP_KERNEL);
+ if (!i2c->adap) {
+ ret = -ENOMEM;
+ goto alloc_failed2;
+ }
+
+ for (i = 0; i < pdata->gpios; i++) {
+ ret = gpio_request(pdata->gpio[i], "i2c-gpiomux");
+ if (ret)
+ goto err_request_gpio;
+ gpio_direction_output(pdata->gpio[i], pdata->idle & (1<<i));
+ }
+
+ for (i = 0; i < pdata->busses; i++) {
+ i2c->adap[i] = gpiomux_adapter;
+ i2c->adap[i].dev.parent = &adap->dev;
+ i2c->adap[i].nr = pdata->base_nr + i;
+
+ snprintf(i2c->adap[i].name, I2C_NAME_SIZE, "%s.%d",
+ gpiomux_adapter.name, i);
+ i2c_set_adapdata(&i2c->adap[i], i2c);
+ ret = i2c_add_numbered_adapter(&i2c->adap[i]);
+ if (ret) {
+ dev_err(&pdev->dev, "Failed to add adapter %d\n", i);
+ goto add_adapter_failed;
+ }
+ }
+
+ dev_info(&pdev->dev, "%d port mux on %s adapter\n",
+ pdata->busses, adap->name);
+
+ platform_set_drvdata(pdev, i2c);
+
+ return 0;
+
+ add_adapter_failed:
+ for (j = 0; j < i; j++)
+ i2c_del_adapter(&i2c->adap[j]);
+ i = pdata->gpios;
+ err_request_gpio:
+ for (j = 0; j < i; j++)
+ gpio_free(pdata->gpio[j]);
+ kfree(i2c->adap);
+ alloc_failed2:
+ kfree(i2c);
+ alloc_failed:
+ i2c_put_adapter(adap);
+
+ return ret;
+}
+
+static int __devexit gpiomux_remove(struct platform_device *pdev)
+{
+ struct gpiomux_i2c *i2c = platform_get_drvdata(pdev);
+ int i;
+
+ for (i = 0; i < i2c->data.busses; i++)
+ i2c_del_adapter(&i2c->adap[i]);
+
+ for (i = 0; i < i2c->data.gpios; i++)
+ gpio_free(i2c->data.gpio[i]);
+
+ platform_set_drvdata(pdev, NULL);
+ i2c_put_adapter(i2c->parent);
+ kfree(i2c->adap);
+ kfree(i2c);
+
+ return 0;
+}
+
+static struct platform_driver gpiomux_driver = {
+ .probe = gpiomux_probe,
+ .remove = __devexit_p(gpiomux_remove),
+ .driver = {
+ .owner = THIS_MODULE,
+ .name = "i2c-gpiomux",
+ },
+};
+
+static int __init gpiomux_init(void)
+{
+ return platform_driver_register(&gpiomux_driver);
+}
+
+static void __exit gpiomux_exit(void)
+{
+ platform_driver_unregister(&gpiomux_driver);
+}
+
+module_init(gpiomux_init);
+module_exit(gpiomux_exit);
+
+MODULE_DESCRIPTION("GPIO-based I2C multiplexer driver");
+MODULE_AUTHOR("Peter Korsgaard <peter.korsgaard@xxxxxxxxx>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:i2c-gpiomux");
diff --git a/include/linux/i2c-gpiomux.h b/include/linux/i2c-gpiomux.h
new file mode 100644
index 0000000..2388ff2
--- /dev/null
+++ b/include/linux/i2c-gpiomux.h
@@ -0,0 +1,35 @@
+/*
+ * i2c-gpiomux interface to platform code
+ *
+ * Peter Korsgaard <peter.korsgaard@xxxxxxxxx>
+ *
+ * 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_GPIOMUX_H
+#define _LINUX_I2C_GPIOMUX_H
+
+/**
+ * struct gpiomux_i2c_platform_data - Platform-dependent data for i2c-gpiomux
+ * @parent: Parent I2C bus adapter number
+ * @base_nr: Base bus number value to number adapters from
+ * @busses: Number of multiplexer positions (busses to instantiate)
+ * @gpios: Number of gpios used to control MUX
+ * @gpio: Array of @gpios gpio numbers used to control MUX
+ * @values: Array of @bussed bitmasks of gpio settings (low/high) for each
+ * position
+ * @idle: Bitmask to write to MUX when idle
+ */
+struct gpiomux_i2c_platform_data {
+ int parent;
+ int base_nr;
+ int busses;
+ int gpios;
+ unsigned *gpio;
+ unsigned *values;
+ unsigned idle;
+};
+
+#endif /* _LINUX_I2C_GPIOMUX_H */
--
1.7.1
--
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