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>

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

+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 */
+			};
+		};
+	};

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

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

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

+/*
+ * 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");

include/linux/platform_data/i2c-mux-reg.h

+/*
+ * 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 */