linux-kernel - Re: [PATCH v2 04/14] clk: st: Adds Flexgen clock binding

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Date:	Tue, 1 Jul 2014 14:11:53 +0200
From:	Gabriel Fernandez <gabriel.fernandez@...aro.org>
To:	Mark Rutland <mark.rutland@....com>
Cc:	Gabriel FERNANDEZ <gabriel.fernandez@...com>,
	"mturquette@...aro.org" <mturquette@...aro.org>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	Pawel Moll <Pawel.Moll@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"galak@...eaurora.org" <galak@...eaurora.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"kernel@...inux.com" <kernel@...inux.com>,
	Lee Jones <lee.jones@...aro.org>
Subject: Re: [PATCH v2 04/14] clk: st: Adds Flexgen clock binding

Thanks for the review Mark,

I'll rework this documentation to answer all these questions

Thanks

Gabriel

On 30 June 2014 11:26, Mark Rutland <mark.rutland@....com> wrote:
> On Fri, Jun 27, 2014 at 02:25:01PM +0100, Gabriel FERNANDEZ wrote:
>> A Flexgen structure is composed by:
>> - a clock cross bar (represented by a mux element)
>> - a pre and final dividers (represented by a divider and gate elements)
>>
>> Signed-off-by: Gabriel Fernandez <gabriel.fernandez@...aro.org>
>> Acked-by: Peter Griffin <peter.griffin@...aro.org>
>> ---
>>  .../devicetree/bindings/clock/st/st,clkgen.txt     |  5 +++
>>  .../devicetree/bindings/clock/st/st,flexgen.txt    | 48 ++++++++++++++++++++++
>>  2 files changed, 53 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/clock/st/st,flexgen.txt
>>
>> diff --git a/Documentation/devicetree/bindings/clock/st/st,clkgen.txt b/Documentation/devicetree/bindings/clock/st/st,clkgen.txt
>> index 427bad8..78978f1 100644
>> --- a/Documentation/devicetree/bindings/clock/st/st,clkgen.txt
>> +++ b/Documentation/devicetree/bindings/clock/st/st,clkgen.txt
>> @@ -32,6 +32,10 @@ address is common of all subnode.
>>               vcc_node {
>>                       ...
>>               };
>> +
>> +             flexgen_node {
>> +                     ...
>> +             };
>>               ...
>>       };
>>
>> @@ -45,6 +49,7 @@ Each subnode should use the binding discribe in [2]..[7]
>>  [5] Documentation/devicetree/bindings/clock/st,clkgen-prediv.txt
>>  [6] Documentation/devicetree/bindings/clock/st,vcc.txt
>>  [7] Documentation/devicetree/bindings/clock/st,quadfs.txt
>> +[8] Documentation/devicetree/bindings/clock/st,flexgen.txt
>>
>>
>>  Required properties:
>> diff --git a/Documentation/devicetree/bindings/clock/st/st,flexgen.txt b/Documentation/devicetree/bindings/clock/st/st,flexgen.txt
>> new file mode 100644
>> index 0000000..f2d4333
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/clock/st/st,flexgen.txt
>> @@ -0,0 +1,48 @@
>> +Binding for a type of flexgen structure found on certain
>> +STMicroelectronics consumer electronics SoC devices
>> +
>> +This structure includes:
>> +- a clock cross bar (represented by a mux element)
>> +- a pre and final dividers (represented by a divider and gate elements)
>> +
>> +This binding uses the common clock binding[1].
>> +
>> +[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
>> +
>> +Required properties:
>> +- compatible : shall be:
>> +  "st,flexgen"
>
> That looks very vague. Is this a sub-node of a larger block?
>
> Might there be a future flexgen revision that looks different?
>
>> +- #clock-cells : from common clock binding; shall be set to 1.
>
> what does the clock cell represent? Is it just a linear index from 0?
>
>> +- clocks : from common clock binding
>
> This is a completely useless description.
>
> Which clock inputs do you expect clocks for? How many? Are they named?
>
>> +
>> +- clock-output-names : From common clock binding. The block has 4
>> +                       clock outputs but not all of them in a specific instance
>> +                       have to be used in the SoC. If a clock name is left as
>> +                       an empty string then no clock will be created for the
>> +                       output associated with that string index. If fewer than
>> +                       4 strings are provided then no clocks will be created
>> +                       for the remaining outputs.
>
> That's a Linux-internal detail, surely?
>
> Why do we even do that?
>
> Mark.
>
>> +
>> +Example:
>> +
>> +     clockgen-d2@...06000 {
>> +             compatible = "st,clkgen-c32";
>> +             reg = <0x9106000 0x1000>;
>> +
>> +             clk_s_d2_flexgen: clk-s-d2-flexgen {
>> +                     compatible = "st,flexgen";
>> +
>> +                     #clock-cells = <1>;
>> +                     clocks = <&clk_s_d2_quadfs 0>,
>> +                              <&clk_s_d2_quadfs 1>,
>> +                              <&clk_s_d2_quadfs 2>,
>> +                              <&clk_s_d2_quadfs 3>;
>> +
>> +                     clock-output-names = "clk-pix-main-disp",
>> +                                          "clk-pix-pip",
>> +                                          "clk-pix-gdp1",
>> +                                          "clk-pix-gdp2";
>> +             };
>> +     };
>> --
>> 1.9.1
>>
>>
--
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