[PATCH 1/8] i2c: mux-pinctrl: Rework to honor disabled child nodes

[sebastian.hesselbarth@gmail.com (Sebastian Hesselbarth)]

I2C mux pinctrl driver currently determines the number of sub-busses by
counting available pinctrl-names. Unfortunately, this requires each
incarnation of the devicetree node with different available sub-busses
to be rewritten.

This patch reworks i2c-mux-pinctrl driver to count the number of
available sub-nodes instead. The rework should be compatible to the old
way of probing for sub-busses and additionally allows to disable unused
sub-busses with standard DT property status = "disabled".

This also amends the corresponding devicetree binding documentation to
reflect the new functionality to disable unused sub-nodes. While at it,
also fix two references to binding documentation files that miss an "i2c-"
prefix.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
---
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Gregory Clement <gregory.clement@free-electrons.com>
Cc: Gabriel Dobato <dobatog@gmail.com>
Cc: Wolfram Sang <wsa@the-dreams.de>
Cc: Stephen Warren <swarren@wwwdotorg.org>
Cc: linux-i2c at vger.kernel.org
Cc: devicetree at vger.kernel.org
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-kernel at vger.kernel.org
---
 .../devicetree/bindings/i2c/i2c-mux-pinctrl.txt    | 28 ++++-----
 drivers/i2c/muxes/i2c-mux-pinctrl.c                | 70 ++++++++++++++--------
 2 files changed, 59 insertions(+), 39 deletions(-)

diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-pinctrl.txt b/Documentation/devicetree/bindings/i2c/i2c-mux-pinctrl.txt
index ae8af1694e95..24b9fdef8850 100644
--- a/Documentation/devicetree/bindings/i2c/i2c-mux-pinctrl.txt
+++ b/Documentation/devicetree/bindings/i2c/i2c-mux-pinctrl.txt
@@ -28,27 +28,24 @@ Also required are:
 * Standard pinctrl properties that specify the pin mux state for each child
   bus. See ../pinctrl/pinctrl-bindings.txt.
 
-* Standard I2C mux properties. See mux.txt in this directory.
+* Standard I2C mux properties. See i2c-mux.txt in this directory.
 
-* I2C child bus nodes. See mux.txt in this directory.
+* I2C child bus nodes. See i2c-mux.txt in this directory.
 
-For each named state defined in the pinctrl-names property, an I2C child bus
-will be created. I2C child bus numbers are assigned based on the index into
-the pinctrl-names property.
+For each child node that is not disabled by a status != "okay", an I2C
+child bus will be created. I2C child bus numbers are assigned based on the
+order of child nodes.
 
-The only exception is that no bus will be created for a state named "idle". If
-such a state is defined, it must be the last entry in pinctrl-names. For
-example:
-
-	pinctrl-names = "ddc", "pta", "idle"  ->  ddc = bus 0, pta = bus 1
-	pinctrl-names = "ddc", "idle", "pta"  ->  Invalid ("idle" not last)
-	pinctrl-names = "idle", "ddc", "pta"  ->  Invalid ("idle" not last)
+There must be a corresponding pinctrl-names entry for each enabled child
+node at the position of the child node's "reg" property.
 
 Whenever an access is made to a device on a child bus, the relevant pinctrl
 state will be programmed into hardware.
 
-If an idle state is defined, whenever an access is not being made to a device
-on a child bus, the idle pinctrl state will be programmed into hardware.
+Also, there can be an idle pinctrl state defined at the end of possible
+pinctrl states. If an idle state is defined, whenever an access is not being
+made to a device on a child bus, the idle pinctrl state will be programmed
+into hardware.
 
 If an idle state is not defined, the most recently used pinctrl state will be
 left programmed into hardware whenever no access is being made of a device on
@@ -68,6 +65,7 @@ Example:
 		pinctrl-1 = <&state_i2cmux_pta>;
 		pinctrl-2 = <&state_i2cmux_idle>;
 
+		/* Enabled child bus 0 */
 		i2c at 0 {
 			reg = <0>;
 			#address-cells = <1>;
@@ -79,10 +77,12 @@ Example:
 			};
 		};
 
+		/* Disabled child bus 1 */
 		i2c at 1 {
 			reg = <1>;
 			#address-cells = <1>;
 			#size-cells = <0>;
+			status = "disabled";
 
 			eeprom {
 				compatible = "eeprom";
diff --git a/drivers/i2c/muxes/i2c-mux-pinctrl.c b/drivers/i2c/muxes/i2c-mux-pinctrl.c
index b48378c4b40d..033dacfabfdf 100644
--- a/drivers/i2c/muxes/i2c-mux-pinctrl.c
+++ b/drivers/i2c/muxes/i2c-mux-pinctrl.c
@@ -56,9 +56,12 @@ static int i2c_mux_pinctrl_parse_dt(struct i2c_mux_pinctrl *mux,
 				struct platform_device *pdev)
 {
 	struct device_node *np = pdev->dev.of_node;
-	int num_names, i, ret;
+	struct device_node *child;
+	struct property *prop;
+	int num_names, num_children, ret;
 	struct device_node *adapter_np;
 	struct i2c_adapter *adapter;
+	const char *state;
 
 	if (!np)
 		return 0;
@@ -77,32 +80,16 @@ static int i2c_mux_pinctrl_parse_dt(struct i2c_mux_pinctrl *mux,
 		return num_names;
 	}
 
-	mux->pdata->pinctrl_states = devm_kzalloc(&pdev->dev,
-		sizeof(*mux->pdata->pinctrl_states) * num_names,
-		GFP_KERNEL);
-	if (!mux->pdata->pinctrl_states) {
-		dev_err(mux->dev, "Cannot allocate pinctrl_states\n");
-		return -ENOMEM;
+	num_children = of_get_available_child_count(np);
+	if (num_children < 0) {
+		dev_err(mux->dev, "Unable to count available children: %d\n",
+			num_children);
+		return num_children;
 	}
 
-	for (i = 0; i < num_names; i++) {
-		ret = of_property_read_string_index(np, "pinctrl-names", i,
-			&mux->pdata->pinctrl_states[mux->pdata->bus_count]);
-		if (ret < 0) {
-			dev_err(mux->dev, "Cannot parse pinctrl-names: %d\n",
-				ret);
-			return ret;
-		}
-		if (!strcmp(mux->pdata->pinctrl_states[mux->pdata->bus_count],
-			    "idle")) {
-			if (i != num_names - 1) {
-				dev_err(mux->dev, "idle state must be last\n");
-				return -EINVAL;
-			}
-			mux->pdata->pinctrl_state_idle = "idle";
-		} else {
-			mux->pdata->bus_count++;
-		}
+	if (num_names < num_children) {
+		dev_err(mux->dev, "Found less pinctrl states than children\n");
+		return -EINVAL;
 	}
 
 	adapter_np = of_parse_phandle(np, "i2c-parent", 0);
@@ -118,6 +105,39 @@ static int i2c_mux_pinctrl_parse_dt(struct i2c_mux_pinctrl *mux,
 	mux->pdata->parent_bus_num = i2c_adapter_id(adapter);
 	put_device(&adapter->dev);
 
+	mux->pdata->pinctrl_states = devm_kzalloc(&pdev->dev,
+		sizeof(*mux->pdata->pinctrl_states) * num_children,
+		GFP_KERNEL);
+	if (!mux->pdata->pinctrl_states) {
+		dev_err(mux->dev, "Cannot allocate pinctrl_states\n");
+		return -ENOMEM;
+	}
+
+	of_property_for_each_string(np, "pinctrl-names", prop, state)
+		if (!strcmp(state, "idle"))
+			mux->pdata->pinctrl_state_idle = "idle";
+
+	for_each_available_child_of_node(np, child) {
+		u32 reg;
+
+		ret = of_property_read_u32(child, "reg", &reg);
+		if (ret < 0) {
+			dev_err(mux->dev, "Missing reg property for child node: %d\n",
+				ret);
+			return ret;
+		}
+
+		ret = of_property_read_string_index(np,
+				    "pinctrl-names", reg, &state);
+		if (ret < 0) {
+			dev_err(mux->dev, "Cannot parse pinctrl-names for mux %d: %d\n",
+				reg, ret);
+			return ret;
+		}
+
+		mux->pdata->pinctrl_states[mux->pdata->bus_count++] = state;
+	}
+
 	return 0;
 }
 #else
-- 
2.1.0