i2c: mux: Add register-based mux i2c-mux-reg

Based on i2c-mux-gpio driver, similarly the register-based mux
switch from one bus to another by setting a single register.
The register can be on PCIe bus, local bus, or any memory-mapped
address. The endianness of such register can be specified in device
tree if used, or in platform data.

Signed-off-by: York Sun <yorksun@freescale.com>
Acked-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

5 files changed, 424 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-reg.txt b/Documentation/devicetree/bindings/i2c/i2c-mux-reg.txt
new file mode 100644
index 000000000000..688783fbe696
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/i2c-mux-reg.txt
@@ -0,0 +1,74 @@
+Register-based I2C Bus Mux
+
+This binding describes an I2C bus multiplexer that uses a single register
+to route the I2C signals.
+
+Required properties:
+- compatible: i2c-mux-reg
+- i2c-parent: The phandle of the I2C bus that this multiplexer's master-side
+  port is connected to.
+* Standard I2C mux properties. See mux.txt in this directory.
+* I2C child bus nodes. See mux.txt in this directory.
+
+Optional properties:
+- reg: this pair of <offset size> specifies the register to control the mux.
+  The <offset size> depends on its parent node. It can be any memory-mapped
+  address. The size must be either 1, 2, or 4 bytes. If reg is omitted, the
+  resource of this device will be used.
+- little-endian: The existence indicates the register is in little endian.
+- big-endian: The existence indicates the register is in big endian.
+  If both little-endian and big-endian are omitted, the endianness of the
+  CPU will be used.
+- write-only: The existence indicates the register is write-only.
+- idle-state: value to set the muxer to when idle. When no value is
+  given, it defaults to the last value used.
+
+Whenever an access is made to a device on a child bus, the value set
+in the revelant node's reg property will be output to the register.
+
+If an idle state is defined, using the idle-state (optional) property,
+whenever an access is not being made to a device on a child bus, the
+register will be set according to the idle value.
+
+If an idle state is not defined, the most recently used value will be
+left programmed into the register.
+
+Example of a mux on PCIe card, the host is a powerpc SoC (big endian):
+
+        i2c-mux {
+                /* the <offset size> depends on the address translation
+                 * of the parent device. If omitted, device resource
+                 * will be used instead. The size is to determine
+                 * whether iowrite32, iowrite16, or iowrite8 will be used.
+                 */
+                reg = <0x6028 0x4>;
+                little-endian;          /* little endian register on PCIe */
+                compatible = "i2c-mux-reg";
+                #address-cells = <1>;
+                #size-cells = <0>;
+                i2c-parent = <&i2c1>;
+                i2c@0 {
+                        reg = <0>;
+                        #address-cells = <1>;
+                        #size-cells = <0>;
+
+                        si5338: clock-generator@70 {
+                                compatible = "silabs,si5338";
+                                reg = <0x70>;
+                                /* other stuff */
+                        };
+                };
+
+                i2c@1 {
+                        /* data is written using iowrite32 */
+                        reg = <1>;
+                        #address-cells = <1>;
+                        #size-cells = <0>;
+
+                        si5338: clock-generator@70 {
+                                compatible = "silabs,si5338";
+                                reg = <0x70>;
+                                /* other stuff */
+                        };
+                };
+        };
diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
index fdd0769c84a3..f06b0e24673b 100644
--- a/drivers/i2c/muxes/Kconfig
+++ b/drivers/i2c/muxes/Kconfig
@@ -61,4 +61,15 @@ config I2C_MUX_PINCTRL
           This driver can also be built as a module. If so, the module will be
           called pinctrl-i2cmux.
 
+config I2C_MUX_REG
+        tristate "Register-based I2C multiplexer"
+        help
+          If you say yes to this option, support will be included for a
+          register based I2C multiplexer. This driver provides access to
+          I2C busses connected through a MUX, which is controlled
+          by a single register.
+
+          This driver can also be built as a module.  If so, the module
+          will be called i2c-mux-reg.
+
 endmenu
diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
index 465778b5d5dc..e89799b76a92 100644
--- a/drivers/i2c/muxes/Makefile
+++ b/drivers/i2c/muxes/Makefile
@@ -7,5 +7,6 @@ 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
+obj-$(CONFIG_I2C_MUX_REG)       += i2c-mux-reg.o
 
 ccflags-$(CONFIG_I2C_DEBUG_BUS) := -DDEBUG
diff --git a/drivers/i2c/muxes/i2c-mux-reg.c b/drivers/i2c/muxes/i2c-mux-reg.c
new file mode 100644
index 000000000000..86d41d36a783
--- /dev/null
+++ b/drivers/i2c/muxes/i2c-mux-reg.c
@@ -0,0 +1,294 @@
+/*
+ * I2C multiplexer using a single register
+ *
+ * Copyright 2015 Freescale Semiconductor
+ * York Sun  <yorksun@freescale.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ */
+
+#include <linux/i2c.h>
+#include <linux/i2c-mux.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/platform_data/i2c-mux-reg.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+struct regmux {
+        struct i2c_adapter *parent;
+        struct i2c_adapter **adap; /* child busses */
+        struct i2c_mux_reg_platform_data data;
+};
+
+static int i2c_mux_reg_set(const struct regmux *mux, unsigned int chan_id)
+{
+        if (!mux->data.reg)
+                return -EINVAL;
+
+        switch (mux->data.reg_size) {
+        case 4:
+                if (mux->data.little_endian) {
+                        iowrite32(chan_id, mux->data.reg);
+                        if (!mux->data.write_only)
+                                ioread32(mux->data.reg);
+                } else {
+                        iowrite32be(chan_id, mux->data.reg);
+                        if (!mux->data.write_only)
+                                ioread32(mux->data.reg);
+                }
+                break;
+        case 2:
+                if (mux->data.little_endian) {
+                        iowrite16(chan_id, mux->data.reg);
+                        if (!mux->data.write_only)
+                                ioread16(mux->data.reg);
+                } else {
+                        iowrite16be(chan_id, mux->data.reg);
+                        if (!mux->data.write_only)
+                                ioread16be(mux->data.reg);
+                }
+                break;
+        case 1:
+                iowrite8(chan_id, mux->data.reg);
+                if (!mux->data.write_only)
+                        ioread8(mux->data.reg);
+                break;
+        default:
+                pr_err("Invalid register size\n");
+                return -EINVAL;
+        }
+
+        return 0;
+}
+
+static int i2c_mux_reg_select(struct i2c_adapter *adap, void *data,
+                              unsigned int chan)
+{
+        struct regmux *mux = data;
+
+        return i2c_mux_reg_set(mux, chan);
+}
+
+static int i2c_mux_reg_deselect(struct i2c_adapter *adap, void *data,
+                                unsigned int chan)
+{
+        struct regmux *mux = data;
+
+        if (mux->data.idle_in_use)
+                return i2c_mux_reg_set(mux, mux->data.idle);
+
+        return 0;
+}
+
+#ifdef CONFIG_OF
+static int i2c_mux_reg_probe_dt(struct regmux *mux,
+                                        struct platform_device *pdev)
+{
+        struct device_node *np = pdev->dev.of_node;
+        struct device_node *adapter_np, *child;
+        struct i2c_adapter *adapter;
+        struct resource res;
+        unsigned *values;
+        int i = 0;
+
+        if (!np)
+                return -ENODEV;
+
+        adapter_np = of_parse_phandle(np, "i2c-parent", 0);
+        if (!adapter_np) {
+                dev_err(&pdev->dev, "Cannot parse i2c-parent\n");
+                return -ENODEV;
+        }
+        adapter = of_find_i2c_adapter_by_node(adapter_np);
+        if (!adapter)
+                return -EPROBE_DEFER;
+
+        mux->parent = adapter;
+        mux->data.parent = i2c_adapter_id(adapter);
+        put_device(&adapter->dev);
+
+        mux->data.n_values = of_get_child_count(np);
+        if (of_find_property(np, "little-endian", NULL)) {
+                mux->data.little_endian = true;
+        } else if (of_find_property(np, "big-endian", NULL)) {
+                mux->data.little_endian = false;
+        } else {
+#if defined(__BYTE_ORDER) ? __BYTE_ORDER == __LITTLE_ENDIAN : \
+        defined(__LITTLE_ENDIAN)
+                mux->data.little_endian = true;
+#elif defined(__BYTE_ORDER) ? __BYTE_ORDER == __BIG_ENDIAN : \
+        defined(__BIG_ENDIAN)
+                mux->data.little_endian = false;
+#else
+#error Endianness not defined?
+#endif
+        }
+        if (of_find_property(np, "write-only", NULL))
+                mux->data.write_only = true;
+        else
+                mux->data.write_only = false;
+
+        values = devm_kzalloc(&pdev->dev,
+                              sizeof(*mux->data.values) * mux->data.n_values,
+                              GFP_KERNEL);
+        if (!values) {
+                dev_err(&pdev->dev, "Cannot allocate values array");
+                return -ENOMEM;
+        }
+
+        for_each_child_of_node(np, child) {
+                of_property_read_u32(child, "reg", values + i);
+                i++;
+        }
+        mux->data.values = values;
+
+        if (!of_property_read_u32(np, "idle-state", &mux->data.idle))
+                mux->data.idle_in_use = true;
+
+        /* map address from "reg" if exists */
+        if (of_address_to_resource(np, 0, &res)) {
+                mux->data.reg_size = resource_size(&res);
+                if (mux->data.reg_size > 4) {
+                        dev_err(&pdev->dev, "Invalid address size\n");
+                        return -EINVAL;
+                }
+                mux->data.reg = devm_ioremap_resource(&pdev->dev, &res);
+                if (IS_ERR(mux->data.reg))
+                        return PTR_ERR(mux->data.reg);
+        }
+
+        return 0;
+}
+#else
+static int i2c_mux_reg_probe_dt(struct gpiomux *mux,
+                                        struct platform_device *pdev)
+{
+        return 0;
+}
+#endif
+
+static int i2c_mux_reg_probe(struct platform_device *pdev)
+{
+        struct regmux *mux;
+        struct i2c_adapter *parent;
+        struct resource *res;
+        int (*deselect)(struct i2c_adapter *, void *, u32);
+        unsigned int class;
+        int i, ret, nr;
+
+        mux = devm_kzalloc(&pdev->dev, sizeof(*mux), GFP_KERNEL);
+        if (!mux)
+                return -ENOMEM;
+
+        platform_set_drvdata(pdev, mux);
+
+        if (dev_get_platdata(&pdev->dev)) {
+                memcpy(&mux->data, dev_get_platdata(&pdev->dev),
+                        sizeof(mux->data));
+
+                parent = i2c_get_adapter(mux->data.parent);
+                if (!parent)
+                        return -EPROBE_DEFER;
+
+                mux->parent = parent;
+        } else {
+                ret = i2c_mux_reg_probe_dt(mux, pdev);
+                if (ret < 0) {
+                        dev_err(&pdev->dev, "Error parsing device tree");
+                        return ret;
+                }
+        }
+
+        if (!mux->data.reg) {
+                dev_info(&pdev->dev,
+                        "Register not set, using platform resource\n");
+                res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+                mux->data.reg_size = resource_size(res);
+                if (mux->data.reg_size > 4) {
+                        dev_err(&pdev->dev, "Invalid resource size\n");
+                        return -EINVAL;
+                }
+                mux->data.reg = devm_ioremap_resource(&pdev->dev, res);
+                if (IS_ERR(mux->data.reg))
+                        return PTR_ERR(mux->data.reg);
+        }
+
+        mux->adap = devm_kzalloc(&pdev->dev,
+                                 sizeof(*mux->adap) * mux->data.n_values,
+                                 GFP_KERNEL);
+        if (!mux->adap) {
+                dev_err(&pdev->dev, "Cannot allocate i2c_adapter structure");
+                return -ENOMEM;
+        }
+
+        if (mux->data.idle_in_use)
+                deselect = i2c_mux_reg_deselect;
+        else
+                deselect = NULL;
+
+        for (i = 0; i < mux->data.n_values; i++) {
+                nr = mux->data.base_nr ? (mux->data.base_nr + i) : 0;
+                class = mux->data.classes ? mux->data.classes[i] : 0;
+
+                mux->adap[i] = i2c_add_mux_adapter(mux->parent, &pdev->dev, mux,
+                                                   nr, mux->data.values[i],
+                                                   class, i2c_mux_reg_select,
+                                                   deselect);
+                if (!mux->adap[i]) {
+                        ret = -ENODEV;
+                        dev_err(&pdev->dev, "Failed to add adapter %d\n", i);
+                        goto add_adapter_failed;
+                }
+        }
+
+        dev_dbg(&pdev->dev, "%d port mux on %s adapter\n",
+                 mux->data.n_values, mux->parent->name);
+
+        return 0;
+
+add_adapter_failed:
+        for (; i > 0; i--)
+                i2c_del_mux_adapter(mux->adap[i - 1]);
+
+        return ret;
+}
+
+static int i2c_mux_reg_remove(struct platform_device *pdev)
+{
+        struct regmux *mux = platform_get_drvdata(pdev);
+        int i;
+
+        for (i = 0; i < mux->data.n_values; i++)
+                i2c_del_mux_adapter(mux->adap[i]);
+
+        i2c_put_adapter(mux->parent);
+
+        return 0;
+}
+
+static const struct of_device_id i2c_mux_reg_of_match[] = {
+        { .compatible = "i2c-mux-reg", },
+        {},
+};
+MODULE_DEVICE_TABLE(of, i2c_mux_reg_of_match);
+
+static struct platform_driver i2c_mux_reg_driver = {
+        .probe  = i2c_mux_reg_probe,
+        .remove = i2c_mux_reg_remove,
+        .driver = {
+                .name   = "i2c-mux-reg",
+        },
+};
+
+module_platform_driver(i2c_mux_reg_driver);
+
+MODULE_DESCRIPTION("Register-based I2C multiplexer driver");
+MODULE_AUTHOR("York Sun <yorksun@freescale.com>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:i2c-mux-reg");
diff --git a/include/linux/platform_data/i2c-mux-reg.h b/include/linux/platform_data/i2c-mux-reg.h
new file mode 100644
index 000000000000..c68712aadf43
--- /dev/null
+++ b/include/linux/platform_data/i2c-mux-reg.h
@@ -0,0 +1,44 @@
+/*
+ * I2C multiplexer using a single register
+ *
+ * Copyright 2015 Freescale Semiconductor
+ * York Sun <yorksun@freescale.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ */
+
+#ifndef __LINUX_PLATFORM_DATA_I2C_MUX_REG_H
+#define __LINUX_PLATFORM_DATA_I2C_MUX_REG_H
+
+/**
+ * struct i2c_mux_reg_platform_data - Platform-dependent data for i2c-mux-reg
+ * @parent: Parent I2C bus adapter number
+ * @base_nr: Base I2C bus number to number adapters from or zero for dynamic
+ * @values: Array of value for each channel
+ * @n_values: Number of multiplexer channels
+ * @little_endian: Indicating if the register is in little endian
+ * @write_only: Reading the register is not allowed by hardware
+ * @classes: Optional I2C auto-detection classes
+ * @idle: Value to write to mux when idle
+ * @idle_in_use: indicate if idle value is in use
+ * @reg: Virtual address of the register to switch channel
+ * @reg_size: register size in bytes
+ */
+struct i2c_mux_reg_platform_data {
+        int parent;
+        int base_nr;
+        const unsigned int *values;
+        int n_values;
+        bool little_endian;
+        bool write_only;
+        const unsigned int *classes;
+        u32 idle;
+        bool idle_in_use;
+        void __iomem *reg;
+        resource_size_t reg_size;
+};
+
+#endif  /* __LINUX_PLATFORM_DATA_I2C_MUX_REG_H */