Re: [PATCH v2] dt-bindings: drm: rcar-du: Document optional reset properties

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Rob,

On Wed, Mar 15, 2017 at 6:01 PM, Rob Herring <robh@kernel.org> wrote:
> On Mon, Mar 06, 2017 at 05:25:56PM +0100, Geert Uytterhoeven wrote:
>> Document the optional properties for describing module resets, to
>> support resetting display channels and LVDS encoders on R-Car Gen2 and
>> Gen3.
>>
>> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
>> ---
>> See "[v2,1/4] dt-bindings: clock: renesas: cpg-mssr: Document reset control
>> support" (https://patchwork.kernel.org/patch/9536627/) for the format of
>> a reset specifier in the Renesas CPG/MSSR case.
>>
>> E.g. "resets = <&cpg 310>;"
>>
>> v2:
>>   - s/phandles/phandle/.
>> ---
>>  Documentation/devicetree/bindings/display/renesas,du.txt | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/display/renesas,du.txt b/Documentation/devicetree/bindings/display/renesas,du.txt
>> index 1a02f099a0ff0a3a..3db418c827193e82 100644
>> --- a/Documentation/devicetree/bindings/display/renesas,du.txt
>> +++ b/Documentation/devicetree/bindings/display/renesas,du.txt
>> @@ -36,6 +36,16 @@ Required Properties:
>>        When supplied they must be named "dclkin.x" with "x" being the input
>>        clock numerical index.
>>
>> +Optional properties:
>> +  - resets: A list of phandle + reset-specifier pairs, one for each entry in
>> +    the reset-names property.
>> +  - reset-names: Names of the resets. This property is model-dependent.
>> +    - R8A779[0123456] use one reset for a group of one or more successive
>> +      channels, and one reset per LVDS encoder (if available). The resets
>> +      must be named "du.x" with "x" being the numerical index of the lowest
>> +      channel in the group. The LVDS resets must be named "lvds.x" with "x"
>> +      being the LVDS encoder numerical index.
>
> LVDS is not a separate block?

Well... from a hardware point of view, the LVDS encoders and DU channels
are all separate blocks (they have separate reg blocks, clocks, and resets).
But due to the dependencies between the blocks, they're modeled in DT as
a single device, with multiple reg, clocks, and resets properties.

The resets follow the clocks closely, as they're handled by the same block
(CPG/MSSR = Module Standby and Software Reset), except for a few quirks
(e.g. one reset for all DU channels on R-Car Gen2, one reset per pair of
 channels on R-Car Gen3).

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds