Commit 7cd70656d1285b ("drm/bridge: display-connector: implement bus fmts callbacks")
introduced a new mechanism to negotiate bus formats between hdmi connectors and bridges which is to be used e.g. for the jz4780 based CI20 board. In this case dw-hdmi sets up a list of formats in dw_hdmi_bridge_atomic_get_output_bus_fmts(). This includes e.g. MEDIA_BUS_FMT_UYVY8_1X16 which is chosen for the CI20 but only produces a black screen. Analysis revealed an omission in Commit 6c3c719936dafe ("drm/bridge: synopsys: dw-hdmi: add bus format negociation") to check for 8 bit with when adding UYVY8 or YUV8 formats. This fix is based on the observation that max_bpc = 0 when running this function while info->bpc = 8. Adding the proposed patch makes the jz4780/CI20 panel work again with default MEDIA_BUS_FMT_RGB888_1X24 mode. Fixes: 7cd70656d1285b ("drm/bridge: display-connector: implement bus fmts callbacks") Fixes: 6c3c719936dafe ("drm/bridge: synopsys: dw-hdmi: add bus format negociation") Signed-off-by: H. Nikolaus Schaller <h...@goldelico.com> --- drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c index 43e375da131e8..c08e2cc96584c 100644 --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c @@ -2621,11 +2621,13 @@ 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) - output_fmts[i++] = MEDIA_BUS_FMT_UYVY8_1X16; + if (max_bpc >= 8 && info->bpc >= 8) { + if (info->color_formats & DRM_COLOR_FORMAT_YCBCR422) + output_fmts[i++] = MEDIA_BUS_FMT_UYVY8_1X16; - if (info->color_formats & DRM_COLOR_FORMAT_YCBCR444) - output_fmts[i++] = MEDIA_BUS_FMT_YUV8_1X24; + if (info->color_formats & DRM_COLOR_FORMAT_YCBCR444) + output_fmts[i++] = MEDIA_BUS_FMT_YUV8_1X24; + } /* Default 8bit RGB fallback */ output_fmts[i++] = MEDIA_BUS_FMT_RGB888_1X24; -- 2.33.0