[PATCH v13 6/9] dw-hdmi/ingenic-dw-hdmi: repair interworking with hdmi-connector

[H. Nikolaus Schaller]

Hi Paul,

> Am 09.02.2022 um 13:18 schrieb Paul Cercueil <paul at crapouillou.net>:
> 
> Hi Nikolaus,
> 
> Le mer., févr. 2 2022 at 17:31:20 +0100, H. Nikolaus Schaller <hns at goldelico.com> a écrit :
>> Commit 7cd70656d1285b ("drm/bridge: display-connector: implement bus fmts callbacks")
>> introduced a new mechanism to negotiate bus formats between hdmi connector
>> and the synopsys hdmi driver inside the jz4780.
>> By this, the dw-hdmi is no longer the only bridge and sets up a list
>> of formats in dw_hdmi_bridge_atomic_get_output_bus_fmts().
>> This includes MEDIA_BUS_FMT_UYVY8_1X16 which is chosen for the jz4780 but only
>> produces a black screen.
>> This fix is based on the observation that max_bpc = 0 when running this
>> function while info->bpc = 8. Since the formats checks before this always test
>> for max_bpc >= info->pbc indirectly my assumption is that we must check it
>> here as well.
> 
> This fix looks really strange to me, so I'll let the DRM experts comment.

Well, yes. We should maybe look for comments by the synopsys/dw-hdmi specialists.

> 
> It would still be better to move the patch before the introduction of dw-ingenic-hdmi.c, so that once this one is introduced, everything works. This also enables bisectability.

Ok, good.

BR and thanks,
Nikolaus

> 
> Cheers,
> -Paul
> 
> 
>> Adding the proposed patch makes the CI20/jz4780 panel work again in
>> MEDIA_BUS_FMT_RGB888_1X24 mode.
>> Fixes: 7cd70656d1285b ("drm/bridge: display-connector: implement bus fmts callbacks")
>> Signed-off-by: H. Nikolaus Schaller <hns at goldelico.com>
>> ---
>> drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>> index 52e7cd2e020d3..34703a15ee4ff 100644
>> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>> @@ -2620,10 +2620,10 @@ static u32 *dw_hdmi_bridge_atomic_get_output_bus_fmts(struct drm_bridge *bridge,
>> 		output_fmts[i++] = MEDIA_BUS_FMT_RGB101010_1X30;
>> 	}
>> -	if (info->color_formats & DRM_COLOR_FORMAT_YCRCB422)
>> +	if (max_bpc >= info->bpc && info->color_formats & DRM_COLOR_FORMAT_YCRCB422)
>> 		output_fmts[i++] = MEDIA_BUS_FMT_UYVY8_1X16;
>> -	if (info->color_formats & DRM_COLOR_FORMAT_YCRCB444)
>> +	if (max_bpc >= info->bpc && info->color_formats & DRM_COLOR_FORMAT_YCRCB444)
>> 		output_fmts[i++] = MEDIA_BUS_FMT_YUV8_1X24;
>> 	/* Default 8bit RGB fallback */
>> --
>> 2.33.0
> 
>