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    SubjectRe: [RFC 6/8] of: add clock providers
    On Tue, Nov 08, 2011 at 06:19:41PM -0700, Grant Likely wrote:
    > 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@secretlab.ca>
    > ---
    > .../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

    s/clock-output-names/clock-output-name?

    > + 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.

    s/clock-output-names/clock-output-name?

    > +
    > +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>;
    ^
    Comma is missed?

    > + clock-input-name = "baud", "register";
    > + };

    [...]

    > +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,

    According to binding document above, s/clock/clock-input?

    > + &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);

    If it fails to match name, we may want to force 'index' back to 0.

    Also according to binding document above,
    s/clock-input-names/clock-input-name? Hope you do not want to
    change binding document to get them aligned. I have written code
    per binding document :)

    Regards,
    Shawn

    > + return of_clk_get(np, index);
    > +}



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