Re: [PATCH 0/5] Adjustments to common mode behavior

[Mario Limonciello <mario.limonciello@amd.com>]

On 9/24/25 12:13 PM, Timur Kristóf wrote:
> 
> 
> On 9/24/25 18:16, Mario Limonciello wrote:
>> As part of enablement for SI and CIK in DC Timur pointed out some
>> differences in behavior for common mode handling for DC vs non DC
>> code paths. This series lines up the behavior between the two
>> implementations.
>>
> Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
> 
> Thank you Mario, this series makes good sense to me.
> My only worry is this: is it possible that removing the common modes 
> from connectors like DP, HDMI, etc. will regress somebody's setup?

Possibly.  We're not going to know until we try.  I generally prefer not 
to add common modes (hence why I tried to drop them before until we hit 
the Xorg bug report).

If someone complains about this then I see two other directions we can go.

1) to make both DC and non-DC paths apply common modes to eDP,LVDS, DP, 
HDMI.  Make them not apply common modes to VGA and DVI.

2) Enabling common modes /across the board/ but anything not in the EDID 
gets the GPU scalar turned on.

> 
> Two possible cases come to mind:
> 1. When we are unable to read the EDID for some reason
> 2. When the EDID is buggy and/or doesn't contain any modes
> Are these issues real or am I overthinking it?
> 
> Thanks & best regards,
> Timur

Failing to read EDID has happened in the past, but I think with the 
deferred aux message handling that should be cleared up now.

I don't think it's a bug if a monitor doesn't advertise support for 
certain modes.  Honestly I think we've gotten quite lucky that eDP that 
panels worked with non-native resolutions not in the EDID in the first 
place.