Messages in this thread |  | | Date | Tue, 5 May 2026 03:45:01 +0300 | | From | Dmitry Baryshkov <> | | Subject | Re: [PATCH v5 05/10] drm/bridge: dw-hdmi-qp: Add HDMI 2.0 SCDC scrambling and high TMDS clock ratio support |
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On Tue, Apr 28, 2026 at 04:51:46PM +0300, Cristian Ciocaltea wrote: > Hi Dmitry, > > Thanks for taking the time to review the series! > > On 4/28/26 4:38 AM, Dmitry Baryshkov wrote: > > On Sun, Apr 26, 2026 at 03:20:17AM +0300, Cristian Ciocaltea wrote: > >> Enable HDMI 2.0 display modes (e.g. 4K@60Hz) by adding SCDC management > >> for the high TMDS clock ratio and scrambling, required when the TMDS > >> character rate exceeds the 340 MHz HDMI 1.4b limit. > >> > >> A periodic work item monitors the sink's scrambling status to recover > >> from sink-side resets. On hotplug detect, if SCDC scrambling state is > >> out of sync with the driver, trigger a CRTC reset to re-establish the > >> link. > >> > >> Reject modes requiring TMDS rates above 600 MHz, as those fall in the > >> HDMI 2.1 FRL domain which is not supported. In no_hpd configurations, > >> further restrict to 340 MHz since SCDC requires a connected sink. > >> > >> Tested-by: Diederik de Haas <diederik@cknow-tech.com> > >> Tested-by: Maud Spierings <maud_spierings@hotmail.com> > >> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com> > >> --- > >> drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c | 188 ++++++++++++++++++++++++--- > >> 1 file changed, 172 insertions(+), 16 deletions(-) > > > > My main issue with this patch (sorry) is that this adds yet another copy > > of SCDC-related helpers into the driver which already OP_HDMI and other > > helpers. > >
> > >> + > >> + drm_atomic_helper_connector_hdmi_hotplug(connector, > >> + connector_status_connected); > > > > I don't see a forced hotplug event in the existing drivers. Why is it > > necessary? This function is being called from the detect() path. > > For some reason, without it, the connector seems to lose its state after reset: > > [ 2142.982967] dwhdmiqp-rockchip fde80000.hdmi: resetting crtc > [ 2142.994132] rockchip-drm display-subsystem: [drm] HDMI Sink doesn't support RGB, something's wrong. > [ 2143.140827] dwhdmiqp-rockchip fde80000.hdmi: dw_hdmi_qp_bridge_atomic_enable mode=DVI > > Will recheck if that's still the case after the HPD handling rework.
I think so. If it doesn't help, please check that drm_bridge_connector_detect() is called for each hotplug event from the hardware. It should take care of parsing EDID (and thus updating HDMI Sink properties).
-- With best wishes Dmitry
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