Re: [PATCH v5 05/10] drm/bridge: dw-hdmi-qp: Add HDMI 2.0 SCDC scrambling and high TMDS clock ratio support

[Cristian Ciocaltea <cristian.ciocaltea@collabora.com>]

Hi Andy,

On 6/1/26 7:06 AM, Andy Yan wrote:
> Hello,
> 
> On 4/26/26 08:20, 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(-)

[...]

>>   }
>>     static const struct drm_edid *
>> @@ -832,12 +986,12 @@ dw_hdmi_qp_bridge_tmds_char_rate_valid(const struct drm_bridge *bridge,
>>   {
>>       struct dw_hdmi_qp *hdmi = bridge->driver_private;
>>   -    /*
>> -     * TODO: when hdmi->no_hpd is 1 we must not support modes that
>> -     * require scrambling, including every mode with a clock above
>> -     * HDMI14_MAX_TMDSCLK.
>> -     */
>> -    if (rate > HDMI14_MAX_TMDSCLK) {
> 
> The locally defined HDMI14_MAX_TMDSCLK has been removed, we should now use
> HDMI_1_3_CHAR_RATE_MAX, and I think we should apply the same change to
> HDMI20_MAX_TMDSRATE

Yep, already addressed in my local dev branch.  Please note this revision is
obsolete, there's already v6 available and I'm going to submit v7 a bit later
today.

Thanks,
Cristian