[PATCH v14 5/9] drm/bridge: dw-hdmi: repair interworking with hdmi-connector for jz4780

[H. Nikolaus Schaller]

> Am 12.02.2022 um 16:06 schrieb Paul Cercueil <paul at crapouillou.net>:
> 
> Hi Nikolaus,
> 
> 
> Le sam., févr. 12 2022 at 15:19:23 +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.
> 
> Neil pushed a fix yesterday that looks like it could fix your issue.
> The fix is: 1528038385c0 ("drm/bridge: dw-hdmi: use safe format when first in bridge chain")
> 
> Could you try if it does indeed fix your issue?

Sure.

Would have been nice and is a fix addressing same base commit, but is not a replacement for my attempt :(

Fortunately we can have both.

> 
> Cheers,
> -Paul
> 
>> 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.
>> 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 b0d8110dd412c..826a055a7a273 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_YCBCR422)
>> +	if (max_bpc >= info->bpc && info->color_formats & DRM_COLOR_FORMAT_YCBCR422)
>> 		output_fmts[i++] = MEDIA_BUS_FMT_UYVY8_1X16;
>> -	if (info->color_formats & DRM_COLOR_FORMAT_YCBCR444)
>> +	if (max_bpc >= info->bpc && info->color_formats & DRM_COLOR_FORMAT_YCBCR444)
>> 		output_fmts[i++] = MEDIA_BUS_FMT_YUV8_1X24;
>> 	/* Default 8bit RGB fallback */
>> --
>> 2.33.0
> 
>