[PATCH 5.0 067/117] drm/sun4i: DW HDMI: Lower max. supported rate for H6

Greg Kroah-Hartman
2019-04-15T19:12:50Z

From: Jernej Skrabec <jernej.skrabec@siol.net>

commit cd9063757a227cf31ebf5391ccda2bf583b0806e upstream.

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@vger.kernel.org # 5.0
Fixes: 40bb9d3147b2 ("drm/sun4i: Add support for H6 DW HDMI controller")
Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190324190609.32721-1-jernej.skrabec@siol.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

--- 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;