Message-Id: <1334688545-8465-2-git-send-email-swarren@wwwdotorg.org>
Date:	Tue, 17 Apr 2012 12:49:05 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Ben Dooks <ben-linux@...ff.org>,
	Wolfram Sang <w.sang@...gutronix.de>,
	Linus Walleij <linus.walleij@...aro.org>
Cc:	devicetree-discuss@...ts.ozlabs.org, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, Stephen Warren <swarren@...dia.com>
Subject: [PATCH 2/2] i2c: Add generic I2C multiplexer using pinctrl API

From: Stephen Warren <swarren@...dia.com>

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@...dia.com>
---
Note: This patch depends on the latest pinctrl tree. In order to merge
this series into the I2C tree, you'll need to merge the pinctrl tree
into it first. However, the pinctrl tree doesn't yet have a stable tag/branch
that you can merge, so this patch can't actually be committed yet.

 .../devicetree/bindings/i2c/pinctrl-i2cmux.txt     |   66 ++++++
 drivers/i2c/muxes/Kconfig                          |   12 +
 drivers/i2c/muxes/Makefile                         |    1 +
 drivers/i2c/muxes/pinctrl-i2cmux.c                 |  246 ++++++++++++++++++++
 include/linux/pinctrl-i2cmux.h                     |   41 ++++
 5 files changed, 366 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..9e37034
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/pinctrl-i2cmux.txt
@@ -0,0 +1,66 @@
+Pinctrl-based I2C Bus Mux
+
+This binding describes an I2C bus multiplexer that uses the 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 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.
+
+  For each named state defined in the pinctrl-names property, an I2C child bus
+  will be created, with that name. The only exception is that if the pinctrl
+  state named "idle" is defined, no bus will be created for that pinctrl
+  state.
+
+* I2C child bus nodes. See i2cmux.txt.
+
+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";
+
+		i2c-parent = <&i2c1>;
+
+		pinctrl-names = "ddc", "pta", "idle";
+		pinctrl-0 = <&state_i2cmux_ddc>;
+		pinctrl-1 = <&state_i2cmux_pta>;
+		pinctrl-2 = <&state_i2cmux_idle>;
+
+		i2c-bus-ddc {
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			eeprom {
+				compatible = "eeprom";
+				reg = <0x50>;
+			};
+		};
+
+		i2c-bus-pta {
+			#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..bf4928b
--- /dev/null
+++ b/drivers/i2c/muxes/pinctrl-i2cmux.c
@@ -0,0 +1,246 @@
+/*
+ * 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 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)
+		return -ENOMEM;
+
+	num_names = of_property_count_strings(np, "pinctrl-names");
+	if (num_names < 0)
+		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)
+		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)
+			return ret;
+		if (!strcmp(mux->pdata->pinctrl_states[mux->pdata->bus_count],
+			    "idle")) {
+			mux->pdata->pinctrl_state_idle = "idle";
+		} else {
+			mux->pdata->bus_count++;
+		}
+	}
+
+	adapter_np = of_parse_phandle(np, "i2c-parent", 0);
+	if (!adapter_np)
+		return -ENODEV;
+	adapter = of_find_i2c_adapter_by_node(adapter_np);
+	if (!adapter)
+		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) {
+		ret = -ENOMEM;
+		goto err;
+	}
+	platform_set_drvdata(pdev, mux);
+
+	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) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	mux->busses = devm_kzalloc(&pdev->dev,
+				   sizeof(mux->busses) * mux->pdata->bus_count,
+				   GFP_KERNEL);
+	if (!mux->states) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	mux->pinctrl = devm_pinctrl_get(&pdev->dev);
+	if (IS_ERR(mux->pinctrl)) {
+		ret = PTR_ERR(mux->pinctrl);
+		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]);
+			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);
+			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(&pdev->dev, mux->parent,
+						mux, bus, i,
+						mux->pdata->pinctrl_states[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@...dia.com>");
+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

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