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SubjectRe: [RESEND PATCH v5 2/3] dt-bindings: display: atmel: optional video-interface of endpoints
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On 2018-08-03 10:11, jacopo mondi wrote:
> Hi Peter!
>
> On Fri, Aug 03, 2018 at 09:23:07AM +0200, Peter Rosin wrote:
>> With bus-type/bus-width properties in the endpoint nodes, the video-
>> interface of the connection can be specified for cases where the
>> heuristic fails to select the correct output mode. This can happen
>> e.g. if not all RGB pins are routed on the PCB; the driver has no
>> way of knowing this, and needs to be told explicitly.
>>
>> This is critical for the devices that have the "conflicting output
>> formats" issue (SAM9N12, SAM9X5, SAMA5D3), since the most significant
>> RGB bits move around depending on the selected output mode. For
>> devices that do not have the "conflicting output formats" issue
>> (SAMA5D2, SAMA5D4), this is completely irrelevant.
>>
>> Acked-by: Boris Brezillon <boris.brezillon@bootlin.com>
>> Reviewed-by: Rob Herring <robh@kernel.org>
>> Signed-off-by: Peter Rosin <peda@axentia.se>
>> ---
>> .../devicetree/bindings/display/atmel/hlcdc-dc.txt | 26 ++++++++++++++++++++++
>> 1 file changed, 26 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt b/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt
>> index 82f2acb3d374..9de434a8f523 100644
>> --- a/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt
>> +++ b/Documentation/devicetree/bindings/display/atmel/hlcdc-dc.txt
>> @@ -15,6 +15,14 @@ Required children nodes:
>> to external devices using the OF graph reprensentation (see ../graph.txt).
>> At least one port node is required.
>>
>> +Optional properties in grandchild nodes:
>> + Any endpoint grandchild node may specify a desired video interface
>> + according to ../../media/video-interfaces.txt, specifically
>> + - bus-type: must be <0>.
>
> Is there any value in specifying this, if it has a fixed value to
> "autodetect"? I understand it's optional, so if nobody else objects,
> feels free to keep it there.

That's just how media/video-interfaces.txt works.

bus-type 0 means that other properties describe the bus type. In this
case bus-width is specified, so that means a parallel bus. But bus-width
has no meaning (or may not have) if bus-type is non-zero. But checking
that bus-type for zero in the code seemed like overkill to me since the
driver already knows that it is a parallel bus...

TL;DR I'd like to keep it.

>
>> + - bus-width: recognized values are <12>, <16>, <18> and <24>, and
>> + override any output mode selection heuristic, forcing "rgb444",
>> + "rgb565", "rgb666" and "rgb888" respectively.
>> +
>> Example:
>>
>> hlcdc: hlcdc@f0030000 {
>> @@ -50,3 +58,21 @@ Example:
>> #pwm-cells = <3>;
>> };
>> };
>> +
>
> Two blank lines here.
>
>> +
>> +Example 2: With a video interface override to force rgb565; as above
>> +but with these changes/additions:
>> +
>> + &hlcdc {
>> + hlcdc-display-controller {
>> + pinctrl-names = "default";
>> + pinctrl-0 = <&pinctrl_lcd_base &pinctrl_lcd_rgb565>;
>> +
>> + port@0 {
>
> The node has a unit address specified, you're missing a reg = <0>
> property (no big deal, it's an example, but the other one has it)
>
>> + hlcdc_panel_output: endpoint@0 {
>
> Missing reg here too.

I'll fix those (I think they appeared for the original example after I
wrote the patch).

Cheers,
Peter

> Minors apart:
>
> Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
>
> Thanks
> j
>
>> + bus-type = <0>;
>> + bus-width = <16>;
>> + };
>> + };
>> + };
>> + };
>> --
>> 2.11.0
>>

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