[PATCH V2] i2c: Add generic I2C multiplexer using pinctrl API

[PATCH V2] i2c: Add generic I2C multiplexer using pinctrl API

[Stephen Warren]

From: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>

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: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
Acked-by: Linus Walleij <linus.walleij-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
---
v2: Rebase onto David Daney's i2c-mux OF support, including slight binding
    changes. Add more error messages.
---
 .../devicetree/bindings/i2c/pinctrl-i2cmux.txt     |   79 ++++++
 drivers/i2c/muxes/Kconfig                          |   12 +
 drivers/i2c/muxes/Makefile                         |    1 +
 drivers/i2c/muxes/pinctrl-i2cmux.c                 |  277 ++++++++++++++++++++
 include/linux/pinctrl-i2cmux.h                     |   41 +++
 5 files changed, 410 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/i2c/pinctrl-i2cmux.txt
 create mode 100644 drivers/i2c/muxes/pinctrl-i2cmux.c
 create mode 100644 include/linux/pinctrl-i2cmux.h

diff --git a/Documentation/devicetree/bindings/i2c/pinctrl-i2cmux.txt b/Documentation/devicetree/bindings/i2c/pinctrl-i2cmux.txt
new file mode 100644
index 0000000..475f970
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/pinctrl-i2cmux.txt
@@ -0,0 +1,79 @@
+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.
+
+Required properties:
+- compatible: pinctrl-i2cmux
+- 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 = "pinctrl-i2cmux";
+		#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>;
+			};
+		};
+	};
+
diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
index 90b7a01..8602384 100644
--- a/drivers/i2c/muxes/Kconfig
+++ b/drivers/i2c/muxes/Kconfig
@@ -37,4 +37,16 @@ config I2C_MUX_PCA954x
 	  This driver can also be built as a module.  If so, the module
 	  will be called 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
diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
index 4640436..7ba65fc 100644
--- a/drivers/i2c/muxes/Makefile
+++ b/drivers/i2c/muxes/Makefile
@@ -4,5 +4,6 @@
 obj-$(CONFIG_I2C_MUX_GPIO)	+= gpio-i2cmux.o
 obj-$(CONFIG_I2C_MUX_PCA9541)	+= pca9541.o
 obj-$(CONFIG_I2C_MUX_PCA954x)	+= pca954x.o
+obj-$(CONFIG_I2C_MUX_PINCTRL)	+= pinctrl-i2cmux.o
 
 ccflags-$(CONFIG_I2C_DEBUG_BUS) := -DDEBUG
diff --git a/drivers/i2c/muxes/pinctrl-i2cmux.c b/drivers/i2c/muxes/pinctrl-i2cmux.c
new file mode 100644
index 0000000..86b5417
--- /dev/null
+++ b/drivers/i2c/muxes/pinctrl-i2cmux.c
@@ -0,0 +1,277 @@
+/*
+ * 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/pinctrl-i2cmux.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+struct pinctrl_mux {
+	struct device *dev;
+	struct pinctrl_i2cmux_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 pinctrl_mux_select(struct i2c_adapter *adap, void *data, u32 chan)
+{
+	struct pinctrl_mux *mux = data;
+
+	return pinctrl_select_state(mux->pinctrl, mux->states[chan]);
+}
+
+static int pinctrl_mux_deselect(struct i2c_adapter *adap, void *data, u32 chan)
+{
+	struct pinctrl_mux *mux = data;
+
+	return pinctrl_select_state(mux->pinctrl, mux->state_idle);
+}
+
+#ifdef CONFIG_OF
+static int pinctrl_mux_parse_dt(struct pinctrl_mux *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 pinctrl_i2cmux_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 pinctrl_mux_parse_dt(struct pinctrl_mux *mux,
+				       struct platform_device *pdev)
+{
+	return 0;
+}
+#endif
+
+static int __devinit pinctrl_mux_probe(struct platform_device *pdev)
+{
+	struct pinctrl_mux *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 pinctrl_mux\n");
+		ret = -ENOMEM;
+		goto err;
+	}
+	platform_set_drvdata(pdev, mux);
+
+	mux->dev = &pdev->dev;
+
+	mux->pdata = pdev->dev.platform_data;
+	if (!mux->pdata) {
+		ret = pinctrl_mux_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 = pinctrl_mux_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,
+						     pinctrl_mux_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 pinctrl_mux_remove(struct platform_device *pdev)
+{
+	struct pinctrl_mux *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 pinctrl_mux_of_match[] __devinitconst = {
+	{ .compatible = "pinctrl-i2cmux", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, pinctrl_mux_of_match);
+#endif
+
+static struct platform_driver pinctrl_mux_driver = {
+	.driver	= {
+		.name	= "pinctrl-i2cmux",
+		.owner	= THIS_MODULE,
+		.of_match_table = of_match_ptr(pinctrl_mux_of_match),
+	},
+	.probe	= pinctrl_mux_probe,
+	.remove	= __devexit_p(pinctrl_mux_remove),
+};
+module_platform_driver(pinctrl_mux_driver);
+
+MODULE_DESCRIPTION("pinctrl-based I2C multiplexer driver");
+MODULE_AUTHOR("Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:pinctrl-i2cmux");
diff --git a/include/linux/pinctrl-i2cmux.h b/include/linux/pinctrl-i2cmux.h
new file mode 100644
index 0000000..046e420
--- /dev/null
+++ b/include/linux/pinctrl-i2cmux.h
@@ -0,0 +1,41 @@
+/*
+ * pinctrl-i2cmux 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_PINCTRL_I2CMUX_H
+#define _LINUX_PINCTRL_I2CMUX_H
+
+/**
+ * struct pinctrl_i2cmux_platform_data - Platform data for pinctrl-i2cmux
+ * @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 pinctrl_i2cmux_platform_data {
+	int parent_bus_num;
+	int base_bus_num;
+	int bus_count;
+	const char **pinctrl_states;
+	const char *pinctrl_state_idle;
+};
+
+#endif
-- 
1.7.0.4

Re: [PATCH V2] i2c: Add generic I2C multiplexer using pinctrl API

[Wolfram Sang]

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> --- /dev/null
> +++ b/Documentation/devicetree/bindings/i2c/pinctrl-i2cmux.txt
> @@ -0,0 +1,79 @@
> +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.
> +
> +Required properties:
> +- compatible: pinctrl-i2cmux

From what I know, compatible-properties should not be linux-specific
since devicetrees are OS independent. pinctrl-i2cmux sounds
linux-specific to me.

So, is such a binding acceptable meanwhile?

Regards,

   Wolfram

-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

[-- Attachment #2: Digital signature --]
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Re: [PATCH V2] i2c: Add generic I2C multiplexer using pinctrl API

[Stephen Warren]

On 04/24/2012 02:09 PM, Wolfram Sang wrote:
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/i2c/pinctrl-i2cmux.txt
>> @@ -0,0 +1,79 @@
>> +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.
>> +
>> +Required properties:
>> +- compatible: pinctrl-i2cmux
> 
> From what I know, compatible-properties should not be linux-specific
> since devicetrees are OS independent. pinctrl-i2cmux sounds
> linux-specific to me.
> 
> So, is such a binding acceptable meanwhile?

To my mind, "pinctrl" has two meanings: (1) is the Linux internal API
(2) is the pinctrl bindings in
Documentation/devicetree/bindings/pinctrl, which were admittedly
developed strongly based on Linux's pinctrl API needs, but I believe
should be completely agnostic to the pinctrl API, SW, OS, etc., and
hence can be considered a pure representation of hardware.

As such, the "pinctrl" in "pinctrl-i2cmux" above refers to (2) above,
and can be considered a pure HW/binding term.

Re: [PATCH V2] i2c: Add generic I2C multiplexer using pinctrl API

[Linus Walleij]

On Tue, Apr 24, 2012 at 11:02 PM, Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org> wrote:
> On 04/24/2012 02:09 PM, Wolfram Sang wrote:
>>
>> From what I know, compatible-properties should not be linux-specific
>> since devicetrees are OS independent. pinctrl-i2cmux sounds
>> linux-specific to me.
>>
>> So, is such a binding acceptable meanwhile?
>
> To my mind, "pinctrl" has two meanings: (1) is the Linux internal API
> (2) is the pinctrl bindings in
> Documentation/devicetree/bindings/pinctrl, which were admittedly
> developed strongly based on Linux's pinctrl API needs, but I believe
> should be completely agnostic to the pinctrl API, SW, OS, etc., and
> hence can be considered a pure representation of hardware.
>
> As such, the "pinctrl" in "pinctrl-i2cmux" above refers to (2) above,
> and can be considered a pure HW/binding term.

I second Stephens statement.

Now every OS in the world must start to think about these things
as pin controllers. But tt's not like there is competing terminology
anyway, so let's define this before we get into committee meetings...

Yours,
Linus Walleij

Re: [PATCH V2] i2c: Add generic I2C multiplexer using pinctrl API

[Stephen Warren]

On 04/25/2012 05:09 AM, Linus Walleij wrote:
> On Tue, Apr 24, 2012 at 11:02 PM, Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org> wrote:
>> On 04/24/2012 02:09 PM, Wolfram Sang wrote:
>>>
>>> From what I know, compatible-properties should not be linux-specific
>>> since devicetrees are OS independent. pinctrl-i2cmux sounds
>>> linux-specific to me.
>>>
>>> So, is such a binding acceptable meanwhile?
>>
>> To my mind, "pinctrl" has two meanings: (1) is the Linux internal API
>> (2) is the pinctrl bindings in
>> Documentation/devicetree/bindings/pinctrl, which were admittedly
>> developed strongly based on Linux's pinctrl API needs, but I believe
>> should be completely agnostic to the pinctrl API, SW, OS, etc., and
>> hence can be considered a pure representation of hardware.
>>
>> As such, the "pinctrl" in "pinctrl-i2cmux" above refers to (2) above,
>> and can be considered a pure HW/binding term.
> 
> I second Stephens statement.
> 
> Now every OS in the world must start to think about these things
> as pin controllers. But tt's not like there is competing terminology
> anyway, so let's define this before we get into committee meetings...

Rob, Grant, could you please take a look at the binding at the start of
this thread and say if you're OK with the compatible naming, and the
binding in general? Thanks.