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@xxxxxxxxxxxxx>
---
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
