Re: [RFC 6/8] of: add clock providers

Based on work by Ben Herrenschmidt and Jeremy Kerr, this patch adds an
of_clk_get function to allow platforms to retrieve clock data from the
device tree.

Platform register a provider through of_clk_add_provider, which will be
called when a device references the provider's OF node for a clock
reference.

Signed-off-by: Grant Likely <grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>
---
 .../devicetree/bindings/clock/clock-bindings.txt   |  109 +++++++++++++++++
 drivers/of/Kconfig                                 |    6 +
 drivers/of/Makefile                                |    1 +
 drivers/of/clock.c                                 |  129 ++++++++++++++++++++
 include/linux/of_clk.h                             |   37 ++++++
 5 files changed, 282 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/clock/clock-bindings.txt
 create mode 100644 drivers/of/clock.c
 create mode 100644 include/linux/of_clk.h

diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt
new file mode 100644
index 0000000..4770c7e
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt

@@ -0,0 +1,109 @@
+This binding is a work-in-progress, and are based on some experimental
+work by benh[1].
+
+Sources of clock signal can be represented by any node in the device
+tree.  Those nodes are designated as clock providers.  Clock consumer
+nodes use a phandle and clock specifier pair to connect clock provider
+outputs to clock inputs.  Similar to the gpio specifiers, a clock
+specifier is an array of one more more cells identifying the clock
+output on a device.  The length of a clock specifier is defined by the
+value of a #clock-cells property in the clock provider node.
+
+[1] http://patchwork.ozlabs.org/patch/31551/
+
+==Clock providers==
+
+Required properties:
+#clock-cells:	   Number of cells in a clock specifier; typically will be
+		   set to 1
+
+Optional properties:
+clock-output-name: Recommended to be a list of strings of clock output signal
+		   names indexed by the first cell in the clock specifier.
+		   However, the meaning of clock-output-names is domain

+		   specific to the clock provider, and is only provided to
+		   encourage using the same meaning for the majority of clock
+		   providers.  This format may not work for clock providers
+		   using a complex clock specifier format.  In those cases it
+		   is recommended to omit this property and create a binding
+		   specific names property.
+
+		   Clock consumer nodes must never directly reference
+		   the provider's clock-output-names property.

+
+For example:
+
+    oscillator {
+        #clock-cells = <1>;
+        clock-output-name = "ckil", "ckih";
+    };
+
+- this node defines a device with two clock outputs, the first named
+  "ckil" and the second named "ckih".  Consumer nodes always reference
+  clocks by index. The names should reflect the clock output signal
+  names for the device.
+
+==Clock consumers==
+
+Required properties:
+clock-input:	List of phandle and clock specifier pairs, one pair
+		for each clock input to the device.
+clock-input-name: List of clock input name strings sorted in the same
+		order as the clock-input property.  Consumers drivers
+		will use clock-input-name to match clock input names
+		with clock-input specifiers.
+
+For example:
+
+    uart {
+        clock-input = <&osc 1> <&ref 0>;

+struct clk *of_clk_get(struct device_node *np, int index)
+{
+	struct of_phandle_args clkspec;
+	struct clk *clk;
+	int rc;
+
+	if (index < 0)
+		return NULL;
+
+	rc = of_parse_phandle_with_args(np, "clock", "#clock-cells", index,

+					&clkspec);
+	if (rc)
+		return NULL;
+
+	clk = __of_clk_get_from_provider(&clkspec);
+	of_node_put(clkspec.np);
+	return clk;
+}
+
+struct clk *of_clk_get_by_name(struct device_node *np, const char *name)
+{
+	int index = 0;
+
+	if (name)
+		index = of_property_match_string(np, "clock-input-names", name);