Currently resolutions with pixel clock higher than 340 MHz don't work
with H6 HDMI controller. They just produce a blank screen.
Limit maximum pixel clock rate to 340 MHz until scrambling is supported.
Cc: stable@xxxxxxxxxxxxxxx # 5.0
Fixes: 40bb9d3147b2 ("drm/sun4i: Add support for H6 DW HDMI controller")
Signed-off-by: Jernej Skrabec <jernej.skrabec@xxxxxxxx>
---
drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c b/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c
index caea5a9f8f1d..ba4ce576b471 100644
--- a/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c
+++ b/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c
@@ -48,8 +48,13 @@ static enum drm_mode_status
sun8i_dw_hdmi_mode_valid_h6(struct drm_connector *connector,
const struct drm_display_mode *mode)
{
- /* This is max for HDMI 2.0b (4K@60Hz) */
- if (mode->clock > 594000)
+ /*
+ * Controller support maximum of 594 MHz, which correlates to
+ * 4K@60Hz 4:4:4 or RGB. However, for frequencies greater than
+ * 340 MHz scrambling has to be enabled. Because scrambling is
+ * not yet implemented, just limit to 340 MHz for now.
+ */
+ if (mode->clock > 340000)
return MODE_CLOCK_HIGH;
return MODE_OK;
--
2.21.0
