Commit ae58d1e4 authored by Stephen Warren's avatar Stephen Warren Committed by Wolfram Sang
Browse files

i2c: Add generic I2C multiplexer using pinctrl API 



This is useful for SoCs whose I2C module's signals can be routed to
different sets of pins at run-time, using the pinctrl API.

                                 +-----+  +-----+
                                 | dev |  | dev |
    +------------------------+   +-----+  +-----+
    | SoC                    |      |        |
    |                   /----|------+--------+
    |   +---+   +------+     | child bus A, on first set of pins
    |   |I2C|---|Pinmux|     |
    |   +---+   +------+     | child bus B, on second set of pins
    |                   \----|------+--------+--------+
    |                        |      |        |        |
    +------------------------+  +-----+  +-----+  +-----+
                                | dev |  | dev |  | dev |
                                +-----+  +-----+  +-----+

Signed-off-by: default avatarStephen Warren <swarren@nvidia.com>
Acked-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Acked-by: default avatarRob Herring <rob.herring@calxeda.com>
Signed-off-by: default avatarWolfram Sang <w.sang@pengutronix.de>
parent f8f5701b

Documentation/devicetree/bindings/i2c/i2c-mux-pinctrl.txt

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Pinctrl-based I2C Bus Mux



This binding describes an I2C bus multiplexer that uses pin multiplexing to

route the I2C signals, and represents the pin multiplexing configuration

using the pinctrl device tree bindings.



                                 +-----+  +-----+

                                 | dev |  | dev |

    +------------------------+   +-----+  +-----+

    | SoC                    |      |        |

    |                   /----|------+--------+

    |   +---+   +------+     | child bus A, on first set of pins

    |   |I2C|---|Pinmux|     |

    |   +---+   +------+     | child bus B, on second set of pins

    |                   \----|------+--------+--------+

    |                        |      |        |        |

    +------------------------+  +-----+  +-----+  +-----+

                                | dev |  | dev |  | dev |

                                +-----+  +-----+  +-----+



Required properties:

- compatible: i2c-mux-pinctrl

- i2c-parent: The phandle of the I2C bus that this multiplexer's master-side

  port is connected to.



Also required are:



* Standard pinctrl properties that specify the pin mux state for each child

  bus. See ../pinctrl/pinctrl-bindings.txt.



* Standard I2C mux properties. See mux.txt in this directory.



* I2C child bus nodes. See mux.txt in this directory.



For each named state defined in the pinctrl-names property, an I2C child bus

will be created. I2C child bus numbers are assigned based on the index into

the pinctrl-names property.



The only exception is that no bus will be created for a state named "idle". If

such a state is defined, it must be the last entry in pinctrl-names. For

example:



	pinctrl-names = "ddc", "pta", "idle"  ->  ddc = bus 0, pta = bus 1

	pinctrl-names = "ddc", "idle", "pta"  ->  Invalid ("idle" not last)

	pinctrl-names = "idle", "ddc", "pta"  ->  Invalid ("idle" not last)



Whenever an access is made to a device on a child bus, the relevant pinctrl

state will be programmed into hardware.



If an idle state is defined, whenever an access is not being made to a device

on a child bus, the idle pinctrl state will be programmed into hardware.



If an idle state is not defined, the most recently used pinctrl state will be

left programmed into hardware whenever no access is being made of a device on

a child bus.



Example:



	i2cmux {

		compatible = "i2c-mux-pinctrl";

		#address-cells = <1>;

		#size-cells = <0>;



		i2c-parent = <&i2c1>;



		pinctrl-names = "ddc", "pta", "idle";

		pinctrl-0 = <&state_i2cmux_ddc>;

		pinctrl-1 = <&state_i2cmux_pta>;

		pinctrl-2 = <&state_i2cmux_idle>;



		i2c@0 {

			reg = <0>;

			#address-cells = <1>;

			#size-cells = <0>;



			eeprom {

				compatible = "eeprom";

				reg = <0x50>;

			};

		};



		i2c@1 {

			reg = <1>;

			#address-cells = <1>;

			#size-cells = <0>;



			eeprom {

				compatible = "eeprom";

				reg = <0x50>;

			};

		};

	};

drivers/i2c/muxes/Kconfig

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@@ -37,4 +37,16 @@ config I2C_MUX_PCA954x 
	  This driver can also be built as a module.  If so, the module

	  will be called i2c-mux-pca954x.



config I2C_MUX_PINCTRL

	tristate "pinctrl-based I2C multiplexer"

	depends on PINCTRL

	help

	  If you say yes to this option, support will be included for an I2C

	  multiplexer that uses the pinctrl subsystem, i.e. pin multiplexing.

	  This is useful for SoCs whose I2C module's signals can be routed to

	  different sets of pins at run-time.



	  This driver can also be built as a module. If so, the module will be

	  called pinctrl-i2cmux.



endmenu

drivers/i2c/muxes/Makefile

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@@ -4,5 +4,6 @@ 
obj-$(CONFIG_I2C_MUX_GPIO)	+= i2c-mux-gpio.o

obj-$(CONFIG_I2C_MUX_PCA9541)	+= i2c-mux-pca9541.o

obj-$(CONFIG_I2C_MUX_PCA954x)	+= i2c-mux-pca954x.o

obj-$(CONFIG_I2C_MUX_PINCTRL)	+= i2c-mux-pinctrl.o



ccflags-$(CONFIG_I2C_DEBUG_BUS) := -DDEBUG

drivers/i2c/muxes/i2c-mux-pinctrl.c

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/*

 * I2C multiplexer using pinctrl API

 *

 * Copyright (c) 2012, NVIDIA CORPORATION.  All rights reserved.

 *

 * This program is free software; you can redistribute it and/or modify it

 * under the terms and conditions of the GNU General Public License,

 * version 2, as published by the Free Software Foundation.

 *

 * This program is distributed in the hope 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, see <http://www.gnu.org/licenses/>.

 */



#include <linux/i2c.h>

#include <linux/i2c-mux.h>

#include <linux/init.h>

#include <linux/module.h>

#include <linux/of_i2c.h>

#include <linux/pinctrl/consumer.h>

#include <linux/i2c-mux-pinctrl.h>

#include <linux/platform_device.h>

#include <linux/slab.h>



struct i2c_mux_pinctrl {

	struct device *dev;

	struct i2c_mux_pinctrl_platform_data *pdata;

	struct pinctrl *pinctrl;

	struct pinctrl_state **states;

	struct pinctrl_state *state_idle;

	struct i2c_adapter *parent;

	struct i2c_adapter **busses;

};



static int i2c_mux_pinctrl_select(struct i2c_adapter *adap, void *data,

				  u32 chan)

{

	struct i2c_mux_pinctrl *mux = data;



	return pinctrl_select_state(mux->pinctrl, mux->states[chan]);

}



static int i2c_mux_pinctrl_deselect(struct i2c_adapter *adap, void *data,

				    u32 chan)

{

	struct i2c_mux_pinctrl *mux = data;



	return pinctrl_select_state(mux->pinctrl, mux->state_idle);

}



#ifdef CONFIG_OF

static int i2c_mux_pinctrl_parse_dt(struct i2c_mux_pinctrl *mux,

				struct platform_device *pdev)

{

	struct device_node *np = pdev->dev.of_node;

	int num_names, i, ret;

	struct device_node *adapter_np;

	struct i2c_adapter *adapter;



	if (!np)

		return 0;



	mux->pdata = devm_kzalloc(&pdev->dev, sizeof(*mux->pdata), GFP_KERNEL);

	if (!mux->pdata) {

		dev_err(mux->dev,

			"Cannot allocate i2c_mux_pinctrl_platform_data\n");

		return -ENOMEM;

	}



	num_names = of_property_count_strings(np, "pinctrl-names");

	if (num_names < 0) {

		dev_err(mux->dev, "Cannot parse pinctrl-names: %d\n",

			num_names);

		return num_names;

	}



	mux->pdata->pinctrl_states = devm_kzalloc(&pdev->dev,

		sizeof(*mux->pdata->pinctrl_states) * num_names,

		GFP_KERNEL);

	if (!mux->pdata->pinctrl_states) {

		dev_err(mux->dev, "Cannot allocate pinctrl_states\n");

		return -ENOMEM;

	}



	for (i = 0; i < num_names; i++) {

		ret = of_property_read_string_index(np, "pinctrl-names", i,

			&mux->pdata->pinctrl_states[mux->pdata->bus_count]);

		if (ret < 0) {

			dev_err(mux->dev, "Cannot parse pinctrl-names: %d\n",

				ret);

			return ret;

		}

		if (!strcmp(mux->pdata->pinctrl_states[mux->pdata->bus_count],

			    "idle")) {

			if (i != num_names - 1) {

				dev_err(mux->dev, "idle state must be last\n");

				return -EINVAL;

			}

			mux->pdata->pinctrl_state_idle = "idle";

		} else {

			mux->pdata->bus_count++;

		}

	}



	adapter_np = of_parse_phandle(np, "i2c-parent", 0);

	if (!adapter_np) {

		dev_err(mux->dev, "Cannot parse i2c-parent\n");

		return -ENODEV;

	}

	adapter = of_find_i2c_adapter_by_node(adapter_np);

	if (!adapter) {

		dev_err(mux->dev, "Cannot find parent bus\n");

		return -ENODEV;

	}

	mux->pdata->parent_bus_num = i2c_adapter_id(adapter);

	put_device(&adapter->dev);



	return 0;

}

#else

static inline int i2c_mux_pinctrl_parse_dt(struct i2c_mux_pinctrl *mux,

					   struct platform_device *pdev)

{

	return 0;

}

#endif



static int __devinit i2c_mux_pinctrl_probe(struct platform_device *pdev)

{

	struct i2c_mux_pinctrl *mux;

	int (*deselect)(struct i2c_adapter *, void *, u32);

	int i, ret;



	mux = devm_kzalloc(&pdev->dev, sizeof(*mux), GFP_KERNEL);

	if (!mux) {

		dev_err(&pdev->dev, "Cannot allocate i2c_mux_pinctrl\n");

		ret = -ENOMEM;

		goto err;

	}

	platform_set_drvdata(pdev, mux);



	mux->dev = &pdev->dev;



	mux->pdata = pdev->dev.platform_data;

	if (!mux->pdata) {

		ret = i2c_mux_pinctrl_parse_dt(mux, pdev);

		if (ret < 0)

			goto err;

	}

	if (!mux->pdata) {

		dev_err(&pdev->dev, "Missing platform data\n");

		ret = -ENODEV;

		goto err;

	}



	mux->states = devm_kzalloc(&pdev->dev,

				   sizeof(*mux->states) * mux->pdata->bus_count,

				   GFP_KERNEL);

	if (!mux->states) {

		dev_err(&pdev->dev, "Cannot allocate states\n");

		ret = -ENOMEM;

		goto err;

	}



	mux->busses = devm_kzalloc(&pdev->dev,

				   sizeof(mux->busses) * mux->pdata->bus_count,

				   GFP_KERNEL);

	if (!mux->states) {

		dev_err(&pdev->dev, "Cannot allocate busses\n");

		ret = -ENOMEM;

		goto err;

	}



	mux->pinctrl = devm_pinctrl_get(&pdev->dev);

	if (IS_ERR(mux->pinctrl)) {

		ret = PTR_ERR(mux->pinctrl);

		dev_err(&pdev->dev, "Cannot get pinctrl: %d\n", ret);

		goto err;

	}

	for (i = 0; i < mux->pdata->bus_count; i++) {

		mux->states[i] = pinctrl_lookup_state(mux->pinctrl,

						mux->pdata->pinctrl_states[i]);

			if (IS_ERR(mux->states[i])) {

				ret = PTR_ERR(mux->states[i]);

				dev_err(&pdev->dev,

					"Cannot look up pinctrl state %s: %d\n",

					mux->pdata->pinctrl_states[i], ret);

				goto err;

			}

	}

	if (mux->pdata->pinctrl_state_idle) {

		mux->state_idle = pinctrl_lookup_state(mux->pinctrl,

						mux->pdata->pinctrl_state_idle);

		if (IS_ERR(mux->state_idle)) {

			ret = PTR_ERR(mux->state_idle);

			dev_err(&pdev->dev,

				"Cannot look up pinctrl state %s: %d\n",

				mux->pdata->pinctrl_state_idle, ret);

			goto err;

		}



		deselect = i2c_mux_pinctrl_deselect;

	} else {

		deselect = NULL;

	}



	mux->parent = i2c_get_adapter(mux->pdata->parent_bus_num);

	if (!mux->parent) {

		dev_err(&pdev->dev, "Parent adapter (%d) not found\n",

			mux->pdata->parent_bus_num);

		ret = -ENODEV;

		goto err;

	}



	for (i = 0; i < mux->pdata->bus_count; i++) {

		u32 bus = mux->pdata->base_bus_num ?

				(mux->pdata->base_bus_num + i) : 0;



		mux->busses[i] = i2c_add_mux_adapter(mux->parent, &pdev->dev,

						     mux, bus, i,

						     i2c_mux_pinctrl_select,

						     deselect);

		if (!mux->busses[i]) {

			ret = -ENODEV;

			dev_err(&pdev->dev, "Failed to add adapter %d\n", i);

			goto err_del_adapter;

		}

	}



	return 0;



err_del_adapter:

	for (; i > 0; i--)

		i2c_del_mux_adapter(mux->busses[i - 1]);

	i2c_put_adapter(mux->parent);

err:

	return ret;

}



static int __devexit i2c_mux_pinctrl_remove(struct platform_device *pdev)

{

	struct i2c_mux_pinctrl *mux = platform_get_drvdata(pdev);

	int i;



	for (i = 0; i < mux->pdata->bus_count; i++)

		i2c_del_mux_adapter(mux->busses[i]);



	i2c_put_adapter(mux->parent);



	return 0;

}



#ifdef CONFIG_OF

static const struct of_device_id i2c_mux_pinctrl_of_match[] __devinitconst = {

	{ .compatible = "i2c-mux-pinctrl", },

	{},

};

MODULE_DEVICE_TABLE(of, i2c_mux_pinctrl_of_match);

#endif



static struct platform_driver i2c_mux_pinctrl_driver = {

	.driver	= {

		.name	= "i2c-mux-pinctrl",

		.owner	= THIS_MODULE,

		.of_match_table = of_match_ptr(i2c_mux_pinctrl_of_match),

	},

	.probe	= i2c_mux_pinctrl_probe,

	.remove	= __devexit_p(i2c_mux_pinctrl_remove),

};

module_platform_driver(i2c_mux_pinctrl_driver);



MODULE_DESCRIPTION("pinctrl-based I2C multiplexer driver");

MODULE_AUTHOR("Stephen Warren <swarren@nvidia.com>");

MODULE_LICENSE("GPL v2");

MODULE_ALIAS("platform:i2c-mux-pinctrl");

include/linux/i2c-mux-pinctrl.h

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/*

 * i2c-mux-pinctrl platform data

 *

 * Copyright (c) 2012, NVIDIA CORPORATION.  All rights reserved.

 *

 * This program is free software; you can redistribute it and/or modify it

 * under the terms and conditions of the GNU General Public License,

 * version 2, as published by the Free Software Foundation.

 *

 * This program is distributed in the hope 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, see <http://www.gnu.org/licenses/>.

 */



#ifndef _LINUX_I2C_MUX_PINCTRL_H

#define _LINUX_I2C_MUX_PINCTRL_H



/**

 * struct i2c_mux_pinctrl_platform_data - Platform data for i2c-mux-pinctrl

 * @parent_bus_num: Parent I2C bus number

 * @base_bus_num: Base I2C bus number for the child busses. 0 for dynamic.

 * @bus_count: Number of child busses. Also the number of elements in

 *	@pinctrl_states

 * @pinctrl_states: The names of the pinctrl state to select for each child bus

 * @pinctrl_state_idle: The pinctrl state to select when no child bus is being

 *	accessed. If NULL, the most recently used pinctrl state will be left

 *	selected.

 */

struct i2c_mux_pinctrl_platform_data {

	int parent_bus_num;

	int base_bus_num;

	int bus_count;

	const char **pinctrl_states;

	const char *pinctrl_state_idle;

};



#endif

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