linux-kernel - Re: [PATCH v3 2/3] drm: Add bus flag for Sharp-specific signals

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Date:   Sat, 27 Apr 2019 08:32:14 +0200
From:   Sam Ravnborg <sam@...nborg.org>
To:     Paul Cercueil <paul@...pouillou.net>,
        Thierry Reding <thierry.reding@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>, od@...c.me,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] drm: Add bus flag for Sharp-specific signals

Hi Paul

On Fri, Apr 26, 2019 at 01:18:53AM +0200, Paul Cercueil wrote:
> Add the DRM_BUS_FLAG_SHARP_SIGNALS to the drm_bus_flags enum.
> 
> This flags can be used when the display must be driven with the
> Sharp-specific signals SPL, CLS, REV, PS.
> 
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> ---
> 
> Notes:
>     v3: New patch
> 
>  include/drm/drm_connector.h | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 02a131202add..ac7d58fd1e03 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -323,6 +323,8 @@ enum drm_panel_orientation {
>   *					edge of the pixel clock
>   * @DRM_BUS_FLAG_SYNC_SAMPLE_NEGEDGE:	Sync signals are sampled on the falling
>   *					edge of the pixel clock
> + * @DRM_BUS_FLAG_SHARP_SIGNALS:		Set if the Sharp-specific signals
> + *					(SPL, CLS, PS, REV) must be used
>   */
>  enum drm_bus_flags {
>  	DRM_BUS_FLAG_DE_LOW = BIT(0),
> @@ -341,6 +343,7 @@ enum drm_bus_flags {
>  	DRM_BUS_FLAG_SYNC_DRIVE_NEGEDGE = DRM_BUS_FLAG_SYNC_NEGEDGE,
>  	DRM_BUS_FLAG_SYNC_SAMPLE_POSEDGE = DRM_BUS_FLAG_SYNC_NEGEDGE,
>  	DRM_BUS_FLAG_SYNC_SAMPLE_NEGEDGE = DRM_BUS_FLAG_SYNC_POSEDGE,
> +	DRM_BUS_FLAG_SHARP_SIGNALS = BIT(8),
>  };

This solutions looks very good to me.
Now the panel can report to the display driver that is needs the
DRM_BUS_FLAG_SHARP_SIGNALS, so the display driver can adapt to the
connected display.
Obviously not many display drivers will support DRM_BUS_FLAG_SHARP_SIGNALS
but the one that does now no longer need to include panel configuration.

You can add:
Reviewed-by: Sam Ravnborg <sam@...nborg.org>

But we need Thierry or someone else with more knowledge in this
area to comment on this before we can apply it.
drm_bus_flag is today only timing related config, and there be a better
way to do this.

Thierry?

	Sam