Hi,
On 12/02/2022 16:50, H. Nikolaus Schaller wrote:
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.
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@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 */
Please do the same for all other cases and change the patch subject to something more accurate like: "drm/bridge: dw-hdmi: take display info bpc in account for bus formats negociation"
Neil