[U-Boot] [PATCH 06/55] dm: i2c: Add support for multiplexed I2C buses

[Simon Glass <sjg@chromium.org>]

Add a new I2C_MUX uclass. Devices in this class can multiplex between
several I2C buses, selecting them one at a time for use by the system.
The multiplexing mechanism is left to the driver to decide - it may be
controlled by GPIOs, for example.

The uclass supports only two methods: select() and deselect().

Signed-off-by: Simon Glass <sjg@chromium.org>
---

 doc/device-tree-bindings/i2c/i2c-mux.txt |  60 ++++++++++
 drivers/i2c/Kconfig                      |   2 +
 drivers/i2c/Makefile                     |   2 +
 drivers/i2c/muxes/Kconfig                |   8 ++
 drivers/i2c/muxes/Makefile               |   6 +
 drivers/i2c/muxes/i2c-mux-uclass.c       | 198 +++++++++++++++++++++++++++++++
 include/dm/uclass-id.h                   |   1 +
 include/i2c.h                            |  32 +++++
 8 files changed, 309 insertions(+)
 create mode 100644 doc/device-tree-bindings/i2c/i2c-mux.txt
 create mode 100644 drivers/i2c/muxes/Kconfig
 create mode 100644 drivers/i2c/muxes/Makefile
 create mode 100644 drivers/i2c/muxes/i2c-mux-uclass.c

diff --git a/doc/device-tree-bindings/i2c/i2c-mux.txt b/doc/device-tree-bindings/i2c/i2c-mux.txt
new file mode 100644
index 0000000..af84cce
--- /dev/null
+++ b/doc/device-tree-bindings/i2c/i2c-mux.txt
@@ -0,0 +1,60 @@
+Common i2c bus multiplexer/switch properties.
+
+An i2c bus multiplexer/switch will have several child busses that are
+numbered uniquely in a device dependent manner.  The nodes for an i2c bus
+multiplexer/switch will have one child node for each child
+bus.
+
+Required properties:
+- #address-cells = <1>;
+- #size-cells = <0>;
+
+Required properties for child nodes:
+- #address-cells = <1>;
+- #size-cells = <0>;
+- reg : The sub-bus number.
+
+Optional properties for child nodes:
+- Other properties specific to the multiplexer/switch hardware.
+- Child nodes conforming to i2c bus binding
+
+
+Example :
+
+	/*
+	   An NXP pca9548 8 channel I2C multiplexer at address 0x70
+	   with two NXP pca8574 GPIO expanders attached, one each to
+	   ports 3 and 4.
+	 */
+
+	mux at 70 {
+		compatible = "nxp,pca9548";
+		reg = <0x70>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		i2c at 3 {
+			#address-cells = <1>;
+			#size-cells = <0>;
+			reg = <3>;
+
+			gpio1: gpio at 38 {
+				compatible = "nxp,pca8574";
+				reg = <0x38>;
+				#gpio-cells = <2>;
+				gpio-controller;
+			};
+		};
+		i2c at 4 {
+			#address-cells = <1>;
+			#size-cells = <0>;
+			reg = <4>;
+
+			gpio2: gpio at 38 {
+				compatible = "nxp,pca8574";
+				reg = <0x38>;
+				#gpio-cells = <2>;
+				gpio-controller;
+			};
+		};
+	};
diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index 86fb36b..caee3d8 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -73,3 +73,5 @@ config SYS_I2C_UNIPHIER_F
 	help
 	  Support for UniPhier FIFO-builtin I2C controller driver.
 	  This I2C controller is used on PH1-Pro4 or newer UniPhier SoCs.
+
+source "drivers/i2c/muxes/Kconfig"
diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
index d9e912f..dc9e81b 100644
--- a/drivers/i2c/Makefile
+++ b/drivers/i2c/Makefile
@@ -37,3 +37,5 @@ obj-$(CONFIG_SYS_I2C_TEGRA) += tegra_i2c.o
 obj-$(CONFIG_SYS_I2C_UNIPHIER) += i2c-uniphier.o
 obj-$(CONFIG_SYS_I2C_UNIPHIER_F) += i2c-uniphier-f.o
 obj-$(CONFIG_SYS_I2C_ZYNQ) += zynq_i2c.o
+
+obj-y += muxes/
diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
new file mode 100644
index 0000000..a05b32d
--- /dev/null
+++ b/drivers/i2c/muxes/Kconfig
@@ -0,0 +1,8 @@
+config I2C_MUX
+	bool "Suport I2C multiplexers"
+	depends on DM_I2C
+	help
+	  This enables I2C buses to be multiplexed, so that you can select
+	  one of several buses using some sort of control mechanism. The
+	  bus select is handled automatically when that bus is accessed,
+	  using a suitable I2C MUX driver.
diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
new file mode 100644
index 0000000..7583e3a
--- /dev/null
+++ b/drivers/i2c/muxes/Makefile
@@ -0,0 +1,6 @@
+#
+# Copyright (c) 2015 Google, Inc
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+obj-$(CONFIG_I2C_MUX) += i2c-mux-uclass.o
diff --git a/drivers/i2c/muxes/i2c-mux-uclass.c b/drivers/i2c/muxes/i2c-mux-uclass.c
new file mode 100644
index 0000000..3f52bff
--- /dev/null
+++ b/drivers/i2c/muxes/i2c-mux-uclass.c
@@ -0,0 +1,198 @@
+/*
+ * Copyright (c) 2015 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <i2c.h>
+#include <dm/lists.h>
+#include <dm/root.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+/**
+ * struct i2c_mux: Information the uclass stores about an I2C mux
+ *
+ * @selected:	Currently selected mux, or -1 for none
+ * @i2c_bus: I2C bus to use for communcation
+ */
+struct i2c_mux {
+	int selected;
+	struct udevice *i2c_bus;
+};
+
+/**
+ * struct i2c_mux_bus: Information about each bus the mux controls
+ *
+ * @channel: Channel number used to select this bus
+ */
+struct i2c_mux_bus {
+	uint channel;
+};
+
+/* Find out the mux channel number */
+static int i2c_mux_child_post_bind(struct udevice *dev)
+{
+	struct i2c_mux_bus *plat = dev_get_parent_platdata(dev);
+	int channel;
+
+	channel = fdtdec_get_int(gd->fdt_blob, dev->of_offset, "reg", -1);
+	if (channel < 0)
+		return -EINVAL;
+	plat->channel = channel;
+
+	return 0;
+}
+
+/* Find the I2C buses selected by this mux */
+static int i2c_mux_post_bind(struct udevice *mux)
+{
+	const void *blob = gd->fdt_blob;
+	int ret;
+	int offset;
+
+	debug("%s: %s\n", __func__, mux->name);
+	/*
+	 * There is no compatible string in the sub-nodes, so we must manually
+	 * bind these
+	 */
+	for (offset = fdt_first_subnode(blob, mux->of_offset);
+	     offset > 0;
+	     offset = fdt_next_subnode(blob, offset)) {
+		struct udevice *dev;
+		const char *name;
+
+		name = fdt_get_name(blob, offset, NULL);
+		ret = device_bind_driver_to_node(mux, "i2c_mux_bus_drv", name,
+						 offset, &dev);
+		debug("   - bind ret=%d, %s\n", ret, dev ? dev->name : NULL);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+/* Set up the mux ready for use */
+static int i2c_mux_post_probe(struct udevice *mux)
+{
+	struct i2c_mux *priv = dev_get_uclass_priv(mux);
+	int ret;
+
+	debug("%s: %s\n", __func__, mux->name);
+	priv->selected = -1;
+
+	ret = uclass_get_device_by_phandle(UCLASS_I2C, mux, "i2c-parent",
+					   &priv->i2c_bus);
+	if (ret)
+		return ret;
+	debug("%s: bus=%p/%s\n", __func__, priv->i2c_bus, priv->i2c_bus->name);
+
+	return 0;
+}
+
+int i2c_mux_select(struct udevice *dev)
+{
+	struct i2c_mux_bus *plat = dev_get_parent_platdata(dev);
+	struct udevice *mux = dev->parent;
+	struct i2c_mux_ops *ops = i2c_mux_get_ops(mux);
+
+	if (!ops->select)
+		return -ENOSYS;
+
+	return ops->select(mux, dev, plat->channel);
+}
+
+int i2c_mux_deselect(struct udevice *dev)
+{
+	struct i2c_mux_bus *plat = dev_get_parent_platdata(dev);
+	struct udevice *mux = dev->parent;
+	struct i2c_mux_ops *ops = i2c_mux_get_ops(mux);
+
+	if (!ops->deselect)
+		return -ENOSYS;
+
+	return ops->deselect(mux, dev, plat->channel);
+}
+
+static int i2c_mux_bus_set_bus_speed(struct udevice *dev, unsigned int speed)
+{
+	struct udevice *mux = dev->parent;
+	struct i2c_mux *priv = dev_get_uclass_priv(mux);
+	int ret, ret2;
+
+	ret = i2c_mux_select(dev);
+	if (ret)
+		return ret;
+	ret = dm_i2c_set_bus_speed(priv->i2c_bus, speed);
+	ret2 = i2c_mux_deselect(dev);
+
+	return ret ? ret : ret2;
+}
+
+static int i2c_mux_bus_probe(struct udevice *dev, uint chip_addr,
+			     uint chip_flags)
+{
+	struct udevice *mux = dev->parent;
+	struct i2c_mux *priv = dev_get_uclass_priv(mux);
+	struct dm_i2c_ops *ops = i2c_get_ops(priv->i2c_bus);
+	int ret, ret2;
+
+	debug("%s: %s, bus %s\n", __func__, dev->name, priv->i2c_bus->name);
+	if (!ops->probe_chip)
+		return -ENOSYS;
+	ret = i2c_mux_select(dev);
+	if (ret)
+		return ret;
+	ret = ops->probe_chip(priv->i2c_bus, chip_addr, chip_flags);
+	ret2 = i2c_mux_deselect(dev);
+
+	return ret ? ret : ret2;
+}
+
+static int i2c_mux_bus_xfer(struct udevice *dev, struct i2c_msg *msg,
+			    int nmsgs)
+{
+	struct udevice *mux = dev->parent;
+	struct i2c_mux *priv = dev_get_uclass_priv(mux);
+	struct dm_i2c_ops *ops = i2c_get_ops(priv->i2c_bus);
+	int ret, ret2;
+
+	debug("%s: %s, bus %s\n", __func__, dev->name, priv->i2c_bus->name);
+	if (!ops->xfer)
+		return -ENOSYS;
+	ret = i2c_mux_select(dev);
+	if (ret)
+		return ret;
+	ret = ops->xfer(priv->i2c_bus, msg, nmsgs);
+	ret2 = i2c_mux_deselect(dev);
+
+	return ret ? ret : ret2;
+}
+
+static const struct dm_i2c_ops i2c_mux_bus_ops = {
+	.xfer		= i2c_mux_bus_xfer,
+	.probe_chip	= i2c_mux_bus_probe,
+	.set_bus_speed	= i2c_mux_bus_set_bus_speed,
+};
+
+U_BOOT_DRIVER(i2c_mux_bus) = {
+	.name		= "i2c_mux_bus_drv",
+	.id		= UCLASS_I2C,
+	.per_child_auto_alloc_size = sizeof(struct dm_i2c_chip),
+	.ops	= &i2c_mux_bus_ops,
+};
+
+UCLASS_DRIVER(i2c_mux) = {
+	.id		= UCLASS_I2C_MUX,
+	.name		= "i2c_mux",
+	.post_bind	= i2c_mux_post_bind,
+	.post_probe	= i2c_mux_post_probe,
+	.per_device_auto_alloc_size = sizeof(struct i2c_mux),
+	.per_child_platdata_auto_alloc_size = sizeof(struct i2c_mux_bus),
+	.child_post_bind = i2c_mux_child_post_bind,
+};
diff --git a/include/dm/uclass-id.h b/include/dm/uclass-id.h
index 72512b5..e2c3480 100644
--- a/include/dm/uclass-id.h
+++ b/include/dm/uclass-id.h
@@ -35,6 +35,7 @@ enum uclass_id {
 	UCLASS_I2C,		/* I2C bus */
 	UCLASS_I2C_EEPROM,	/* I2C EEPROM device */
 	UCLASS_I2C_GENERIC,	/* Generic I2C device */
+	UCLASS_I2C_MUX,		/* I2C multiplexer */
 	UCLASS_LED,		/* Light-emitting diode (LED) */
 	UCLASS_LPC,		/* x86 'low pin count' interface */
 	UCLASS_MASS_STORAGE,	/* Mass storage device */
diff --git a/include/i2c.h b/include/i2c.h
index d191829..a59a19a 100644
--- a/include/i2c.h
+++ b/include/i2c.h
@@ -445,6 +445,38 @@ struct dm_i2c_ops {
 #define i2c_get_ops(dev)	((struct dm_i2c_ops *)(dev)->driver->ops)
 
 /**
+ * struct i2c_mux_ops - operations for an I2C mux
+ */
+struct i2c_mux_ops {
+	/**
+	 * select() - select one of of I2C buses attached to a mux
+	 *
+	 * This will be called when there is no bus currently selected by the
+	 * mux. This method does not need to deselect the old bus.
+	 *
+	 * @mux:	Mux device
+	 * @bus:	I2C bus to select
+	 * @channel:	Channel number correponding to the bus to select
+	 * @return 0 if OK, -ve on error
+	 */
+	int (*select)(struct udevice *mux, struct udevice *bus, uint channel);
+
+	/**
+	 * deselect() - select one of of I2C buses attached to a mux
+	 *
+	 * This is used to deselect the currently selected I2C bus.
+	 *
+	 * @mux:	Mux device
+	 * @bus:	I2C bus to deselect
+	 * @channel:	Channel number correponding to the bus to deselect
+	 * @return 0 if OK, -ve on error
+	 */
+	int (*deselect)(struct udevice *mux, struct udevice *bus, uint channel);
+};
+
+#define i2c_mux_get_ops(dev)	((struct i2c_mux_ops *)(dev)->driver->ops)
+
+/**
  * i2c_get_chip() - get a device to use to access a chip on a bus
  *
  * This returns the device for the given chip address. The device can then
-- 
2.4.3.573.g4eafbef