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: Stephen Warren <swarren@nvidia.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>

5 files changed, 426 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-pinctrl.txt b/Documentation/devicetree/bindings/i2c/i2c-mux-pinctrl.txt
new file mode 100644
index 000000000000..ae8af1694e95
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/i2c-mux-pinctrl.txt
@@ -0,0 +1,93 @@
+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>;
+                        };
+                };
+        };
+
diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
index beb2491db274..a0edd9854218 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 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
diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
index 5826249b29ca..76da8692afff 100644
--- a/drivers/i2c/muxes/Makefile
+++ b/drivers/i2c/muxes/Makefile
@@ -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
diff --git a/drivers/i2c/muxes/i2c-mux-pinctrl.c b/drivers/i2c/muxes/i2c-mux-pinctrl.c
new file mode 100644
index 000000000000..46a669763476
--- /dev/null
+++ b/drivers/i2c/muxes/i2c-mux-pinctrl.c
@@ -0,0 +1,279 @@
+/*
+ * 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");
diff --git a/include/linux/i2c-mux-pinctrl.h b/include/linux/i2c-mux-pinctrl.h
new file mode 100644
index 000000000000..a65c86429e84
--- /dev/null
+++ b/include/linux/i2c-mux-pinctrl.h
@@ -0,0 +1,41 @@
+/*
+ * 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