drm_hdmi_connector_mode_valid assumes modes are only valid if they work
with RGB. The reality is more complex however: YCbCr 4:2:0
chroma-subsampled modes only require half the pixel clock that the same
mode would require in RGB.
This leads to drm_hdmi_connector_mode_valid rejecting perfectly valid
420-only modes.
Fix this by checking whether the mode is 420-only first. If so, then
proceed by checking it with HDMI_COLORSPACE_YUV420 so long as the
connector has legalized 420, otherwise error out. If the mode is not
420-only, check with RGB as was previously always the case.
Fixes: 47368ab437fd ("drm/display: hdmi: add generic mode_valid helper")
Signed-off-by: Nicolas Frattaroli <[email protected]>
---
drivers/gpu/drm/display/drm_hdmi_state_helper.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
index 5da956bdd68c..1800e00b30c5 100644
--- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
+++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
@@ -892,8 +892,18 @@ drm_hdmi_connector_mode_valid(struct drm_connector
*connector,
const struct drm_display_mode *mode)
{
unsigned long long clock;
+ enum hdmi_colorspace fmt;
+
+ if (drm_mode_is_420_only(&connector->display_info, mode)) {
+ if (connector->ycbcr_420_allowed)
+ fmt = HDMI_COLORSPACE_YUV420;
+ else
+ return MODE_NO_420;
+ } else {
+ fmt = HDMI_COLORSPACE_RGB;
+ }
- clock = drm_hdmi_compute_mode_clock(mode, 8, HDMI_COLORSPACE_RGB);
+ clock = drm_hdmi_compute_mode_clock(mode, 8, fmt);
if (!clock)
return MODE_ERROR;
--
2.52.0
