From: York Sun <yorksun@freescale.com>
To: <wsa@the-dreams.de>
CC: <linux-kernel@vger.kernel.org>, <linux-i2c@vger.kernel.org>,
        York Sun <yorksun@freescale.com>,
        Peter Korsgaard <peter.korsgaard@barco.com>
Subject: [PATCH] driver/i2c/mux: Add register based mux i2c-mux-reg
Date: Tue, 16 Jun 2015 10:28:12 -0700
Message-ID: <1434475692-4611-1-git-send-email-yorksun@freescale.com>
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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.

Signed-off-by: York Sun <yorksun@freescale.com>
CC: Wolfram Sang <wsa@the-dreams.de>
CC: Peter Korsgaard <peter.korsgaard@barco.com>
---
 .../devicetree/bindings/i2c/i2c-mux-reg.txt        |   69 ++++++
 drivers/i2c/muxes/Kconfig                          |   11 +
 drivers/i2c/muxes/Makefile                         |    1 +
 drivers/i2c/muxes/i2c-mux-reg.c                    |  239 ++++++++++++++++++++
 drivers/i2c/muxes/i2c-mux-reg.h                    |   38 ++++
 5 files changed, 358 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/i2c/i2c-mux-reg.txt
 create mode 100644 drivers/i2c/muxes/i2c-mux-reg.c
 create mode 100644 drivers/i2c/muxes/i2c-mux-reg.h

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 0000000..ad7cc4f
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/i2c-mux-reg.txt
@@ -0,0 +1,69 @@
+Register-based I2C Bus Mux
+
+This binding describes an I2C bus multiplexer that uses a single regsiter
+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. If omitted, the resource of this device will be used.
+- idle-state: value to set the muxer to when idle. When no value is
+  given, it defaults to the last value used.
+
+For each i2c child node, an I2C child bus will be created. They will
+be numbered based on their order in the device tree.
+
+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.
+		 */
+		reg = <0x6028 0x4>;
+		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 in little endian on pcie bus */
+			reg = <0x01000000>;
+			#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 f6d313e..77c1257 100644
--- a/drivers/i2c/muxes/Kconfig
+++ b/drivers/i2c/muxes/Kconfig
@@ -29,6 +29,17 @@ config I2C_MUX_GPIO
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-mux-gpio.
 
+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 sinple register.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called i2c-mux-reg.
+
 config I2C_MUX_PCA9541
 	tristate "NXP PCA9541 I2C Master Selector"
 	help
diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
index 465778b..bc517bb 100644
--- a/drivers/i2c/muxes/Makefile
+++ b/drivers/i2c/muxes/Makefile
@@ -4,6 +4,7 @@
 obj-$(CONFIG_I2C_ARB_GPIO_CHALLENGE)	+= i2c-arb-gpio-challenge.o
 
 obj-$(CONFIG_I2C_MUX_GPIO)	+= i2c-mux-gpio.o
+obj-$(CONFIG_I2C_MUX_REG)	+= i2c-mux-reg.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
diff --git a/drivers/i2c/muxes/i2c-mux-reg.c b/drivers/i2c/muxes/i2c-mux-reg.c
new file mode 100644
index 0000000..03ce858
--- /dev/null
+++ b/drivers/i2c/muxes/i2c-mux-reg.c
@@ -0,0 +1,239 @@
+/*
+ * 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 version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/i2c.h>
+#include <linux/i2c-mux.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include "i2c-mux-reg.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)
+{
+	if (!mux->data.reg || chan < 0 || chan > mux->data.n_values)
+		return -EINVAL;
+
+	*mux->data.reg = mux->data.values[chan];
+
+	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;
+
+	return i2c_mux_reg_set(mux, mux->data.idle);
+}
+
+#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) {
+		dev_err(&pdev->dev, "Cannot find parent bus\n");
+		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);
+
+	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 = I2C_MUX_REG_NO_IDLE;
+
+	/* map address from "reg" if exists */
+	if (!of_address_to_resource(np, 0, &res)) {
+		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 initial_state, 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) {
+			dev_err(&pdev->dev, "Parent adapter (%d) not found\n",
+				mux->data.parent);
+			return -EPROBE_DEFER;
+		}
+		mux->parent = parent;
+		i2c_put_adapter(parent);
+	} else {
+		ret = i2c_mux_reg_probe_dt(mux, pdev);
+		if (ret < 0) {
+			dev_err(&pdev->dev, "Cannot locate 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 = 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 != I2C_MUX_REG_NO_IDLE) {
+		initial_state = mux->data.idle;
+		deselect = i2c_mux_reg_deselect;
+	} else {
+		initial_state = mux->data.values[0];
+		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_info(&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);
+
+	dev_info(&pdev->dev, "Removed\n");
+
+	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	= {
+		.owner	= THIS_MODULE,
+		.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/drivers/i2c/muxes/i2c-mux-reg.h b/drivers/i2c/muxes/i2c-mux-reg.h
new file mode 100644
index 0000000..e213988
--- /dev/null
+++ b/drivers/i2c/muxes/i2c-mux-reg.h
@@ -0,0 +1,38 @@
+/*
+ * 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 version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __LINUX_I2C_MUX_REG_H
+#define __LINUX_I2C_MUX_REG_H
+
+/* MUX has no specific idel mode */
+#define I2C_MUX_REG_NO_IDLE	((unsigned)-1)
+
+/**
+ * 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
+ * @classes: Optional I2C auto-detection classes
+ * @idle: Value to write to mux when idle
+ * @reg: Virtual address of the register to switch channel
+ */
+struct i2c_mux_reg_platform_data {
+	int parent;
+	int base_nr;
+	const unsigned int *values;
+	int n_values;
+	const unsigned int *classes;
+	unsigned int idle;
+	unsigned int *reg;
+};
+
+#endif	/* __LINUX_I2C_MUX_REG_H */
-- 
1.7.9.5

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