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 <s...@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@70 {
+               compatible = "nxp,pca9548";
+               reg = <0x70>;
+               #address-cells = <1>;
+               #size-cells = <0>;
+
+               i2c@3 {
+                       #address-cells = <1>;
+                       #size-cells = <0>;
+                       reg = <3>;
+
+                       gpio1: gpio@38 {
+                               compatible = "nxp,pca8574";
+                               reg = <0x38>;
+                               #gpio-cells = <2>;
+                               gpio-controller;
+                       };
+               };
+               i2c@4 {
+                       #address-cells = <1>;
+                       #size-cells = <0>;
+                       reg = <4>;
+
+                       gpio2: gpio@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 <s...@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

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