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    SubjectRe: [PATCH] clk: Add device tree binding to clk-fixed-factor
    On 04/11/2013 11:19 AM, Christian Ruppert wrote:
    > Hi Gregory,
    >
    > Since there doesn't seem to be anyone opposing this feature I just
    > checked your patch and after adding the CLK_OF_DECLARE macro in the end
    > it works well for us. Tell me if you would like to rebase and resubmit
    > your patch or if I should follow up on our own.

    I can rebase and resubmit my patch, it's pretty straightforward.
    The problem was the lack of user in the kernel. And by user I mean
    a driver using these functions. Usually a new function enter in the
    kernel only if there are users for it inside the kernel so if you plan
    to submit a driver using this piece of code, then I see no reason
    to not get it.

    >
    > Greetings,
    > Christian
    >
    > On Wed, Apr 10, 2013 at 06:27:47PM +0200, christian ruppert wrote:
    >> Hi Gregory,
    >>
    >> We use derived clocks with fixed ratios for our TB10x platform. I
    >> originally had this in the platform code but Vineet (the platform
    >> maintainer) rightly pointed out that the common clock framework would
    >> be the correct place for it.
    >> Is there any reason not to support this functionality? After all, the
    >> generic fixed rate clock also has a device tree binding and I'd guess
    >> we're not the only ones statically deriving one clock from another in
    >> our SOCs.
    >>
    >> Greetings,
    >> Christian
    >>
    >> On Wed, Apr 10, 2013 at 05:56:25PM +0200, Gregory CLEMENT wrote:
    >>> Hi Christian,
    >>>
    >>> On 04/10/2013 05:40 PM, Christian Ruppert wrote:
    >>>> This patch adds a device tree binding for the simple fixed factor clock
    >>>> divider/multiplier of the common clock tree binding.
    >>>
    >>> This patch remind me of something :
    >>> http://lists.infradead.org/pipermail/linux-arm-kernel/2012-August/116405.html
    >>>
    >>> Do you have a use case for it, this time?
    >>>
    >>> My version have been hold off waiting for an user for it.
    >>> Will you need it for a driver?
    >>>
    >>> Regards,
    >>>
    >>>>
    >>>> Signed-off-by: Christian Ruppert <christian.ruppert@abilis.com>
    >>>> ---
    >>>> .../bindings/clock/fixed-factor-clkdiv.txt | 24 +++++++++++++++
    >>>> drivers/clk/clk-fixed-factor.c | 32 ++++++++++++++++++++
    >>>> include/linux/clk-provider.h | 1 +
    >>>> 3 files changed, 57 insertions(+), 0 deletions(-)
    >>>> create mode 100644 Documentation/devicetree/bindings/clock/fixed-factor-clkdiv.txt
    >>>>
    >>>> diff --git a/Documentation/devicetree/bindings/clock/fixed-factor-clkdiv.txt b/Documentation/devicetree/bindings/clock/fixed-factor-clkdiv.txt
    >>>> new file mode 100644
    >>>> index 0000000..352bac4
    >>>> --- /dev/null
    >>>> +++ b/Documentation/devicetree/bindings/clock/fixed-factor-clkdiv.txt
    >>>> @@ -0,0 +1,24 @@
    >>>> +Device Tree Clock bindings for plat-tb10x
    >>>> +
    >>>> +This binding uses the common clock binding[1].
    >>>> +
    >>>> +[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
    >>>> +
    >>>> +Required properties:
    >>>> +- compatible : shall be "fixed-factor-clkdiv"
    >>>> +- #clock-cells: from common clock binding; shall be set to 0
    >>>> +- clocks: shall be the input parent clock phandle for the clock.
    >>>> +- clock-mult: defines the multiplication factor of the output clock frequency
    >>>> + wrt. the input clock frequency.
    >>>> +- clock-div: defines the division factor of the output clock frequency wrt.
    >>>> + the input clock frequency.
    >>>> +
    >>>> +Example:
    >>>> +cpu_clk: clkdiv_cpu { /* CPU clock derived from pll0. 1/2 of pll frequency */
    >>>> + compatible = "fixed-factor-clkdiv";
    >>>> + #clock-cells = <0>;
    >>>> + clocks = <&pll0>;
    >>>> + clock-mult = <1>;
    >>>> + clock-div = <2>;
    >>>> + clock-output-names = "cpu_clk";
    >>>> +};
    >>>> diff --git a/drivers/clk/clk-fixed-factor.c b/drivers/clk/clk-fixed-factor.c
    >>>> index 1ef271e..85e45f1 100644
    >>>> --- a/drivers/clk/clk-fixed-factor.c
    >>>> +++ b/drivers/clk/clk-fixed-factor.c
    >>>> @@ -11,6 +11,7 @@
    >>>> #include <linux/clk-provider.h>
    >>>> #include <linux/slab.h>
    >>>> #include <linux/err.h>
    >>>> +#include <linux/of.h>
    >>>>
    >>>> /*
    >>>> * DOC: basic fixed multiplier and divider clock that cannot gate
    >>>> @@ -96,3 +97,34 @@ struct clk *clk_register_fixed_factor(struct device *dev, const char *name,
    >>>>
    >>>> return clk;
    >>>> }
    >>>> +
    >>>> +#ifdef CONFIG_OF
    >>>> +/**
    >>>> + * of_fixed_factor_clkdiv_setup() - Set up simple fixed factor clock divider
    >>>> + */
    >>>> +void of_fixed_factor_clkdiv_setup(struct device_node *node)
    >>>> +{
    >>>> + struct clk *clk;
    >>>> + const char *clk_name = node->name;
    >>>> + const char *parent_name;
    >>>> + u32 mult, div;
    >>>> +
    >>>> + if (of_property_read_u32(node, "clock-mult", &mult))
    >>>> + return;
    >>>> +
    >>>> + if (of_property_read_u32(node, "clock-div", &div))
    >>>> + return;
    >>>> +
    >>>> + parent_name = of_clk_get_parent_name(node, 0);
    >>>> +
    >>>> + of_property_read_string(node, "clock-output-names", &clk_name);
    >>>> +
    >>>> + clk = clk_register_fixed_factor(NULL, clk_name, parent_name, 0,
    >>>> + mult, div);
    >>>> + if (!IS_ERR(clk))
    >>>> + of_clk_add_provider(node, of_clk_src_simple_get, clk);
    >>>> +}
    >>>> +EXPORT_SYMBOL_GPL(of_fixed_factor_clkdiv_setup);
    >>>> +CLK_OF_DECLARE(fixed_clkdiv, "fixed-factor-clkdiv",
    >>>> + of_fixed_factor_clkdiv_setup);
    >>>> +#endif
    >>>> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
    >>>> index 7f197d7..d4937cf 100644
    >>>> --- a/include/linux/clk-provider.h
    >>>> +++ b/include/linux/clk-provider.h
    >>>> @@ -184,6 +184,7 @@ struct clk *clk_register_fixed_rate(struct device *dev, const char *name,
    >>>> unsigned long fixed_rate);
    >>>>
    >>>> void of_fixed_clk_setup(struct device_node *np);
    >>>> +void of_fixed_factor_clkdiv_setup(struct device_node *node);
    >>>>
    >>>> /**
    >>>> * struct clk_gate - gating clock
    >>>>
    >>>
    >>>
    >>> --
    >>> Gregory Clement, Free Electrons
    >>> Kernel, drivers, real-time and embedded Linux
    >>> development, consulting, training and support.
    >>> http://free-electrons.com
    >>
    >> --
    >> Christian Ruppert , <christian.ruppert@abilis.com>
    >> /|
    >> Tel: +41/(0)22 816 19-42 //| 3, Chemin du Pré-Fleuri
    >> _// | bilis Systems CH-1228 Plan-les-Ouates
    >


    --
    Gregory Clement, Free Electrons
    Kernel, drivers, real-time and embedded Linux
    development, consulting, training and support.
    http://free-electrons.com
    --
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