Re: [PATCH 2/7] of: add clock providers

From: Grant Likely <grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>

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.

v3: - Clarified documentation

v2: - fixed errant ';' causing compile error
    - Editorial fixes from Shawn Guo
    - merged in adding lookup to clkdev
    - changed property names to match established convention. After
      working with the binding a bit it really made more sense to follow the
      lead of 'reg', 'gpios' and 'interrupts' by making the input simply
      'clocks' & 'clock-names' instead of 'clock-input-*', and to only use
      clock-output* for the producer nodes. (Sorry Shawn, this will mean
      you need to change some code, but it should be trivial)
    - Add ability to inherit clocks from parent nodes by using an empty
      'clock-ranges' property.  Useful for busses.  I could use some feedback
      on the new property name, 'clock-ranges' doesn't feel right to me.

Signed-off-by: Grant Likely <grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>
Reviewed-by: Shawn Guo <redacted>
Cc: Rob Herring <rob.herring-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org>
Cc: Sascha Hauer <redacted>
Cc: Mike Turquette <redacted>
---
 .../devicetree/bindings/clock/clock-bindings.txt   |  116 ++++++++++++++
 .../devicetree/bindings/clock/fixed-clock.txt      |   21 +++
 drivers/clk/clkdev.c                               |    9 +
 drivers/of/Kconfig                                 |    6 +
 drivers/of/Makefile                                |    1 +
 drivers/of/clock.c                                 |  165 ++++++++++++++++++++
 include/linux/of_clk.h                             |   37 +++++
 7 files changed, 355 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/clock/clock-bindings.txt
 create mode 100644 Documentation/devicetree/bindings/clock/fixed-clock.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..3cb6746
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt

@@ -0,0 +1,116 @@
+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
+