[SRU][OEM-5.14/Jammy/OEM-5.17][PATCH 0/1] Fix blank screen on Thinkpad ADL 4K+ panel

[Aaron Ma]

On 7/8/22 17:12, Stefan Bader wrote:
> On 04.07.22 07:15, Aaron Ma wrote:
>> BugLink: https://bugs.launchpad.net/bugs/1980621
>>
>> [Impact]
>> Set screen off on ThinkPad P1G5 with 4k+ panel.
>> The screen will never be back.
>>
>> [Fix]
>> It's a upstream kernel regression.
>> And reverted by upstream.
>>
>> [Test]
>> Verified on hardware, screen on/off 20 times OK.
>>
>> [Where problems could occur]
>> Low risk, it reverts a regression and may break i915 driver.
>>
>> On 5.14-oem and Jammy kernel, This commit was claimed to backport
>> commit 73867c8709b5 ("drm/i915/display: Remove check for low voltage sku for max dp source rate")
>> But it's not kind of it.
>> So revert it instead.
>>
>> On 5.17 kernel, revert it by upstream commit.
>>
>> Unstable kernel already got it.
>>
>> Jason A. Donenfeld (1):
>>    drm/i915/display: Re-add check for low voltage sku for max dp source
>>      rate
>>
>> Aaron Ma (1):
>>    UBUNTU: SAUCE: Revert "drm/i915/display: Remove check for low voltage
>>      sku for max dp source rate"
>>
>>   drivers/gpu/drm/i915/display/intel_dp.c | 32 ++++++++++++++++++++++---
>>   1 file changed, 29 insertions(+), 3 deletions(-)
>>
>
> This would be a case where it would be good also say what was the original problem that the patch to be reverted tried to solve. But also the fact that the patch in Jammy claims to be a cherry pick but is completely different from the upstream patch, yet the SHA1 _are_ identical.
>

The original problem did fix a problem but introduced a new one.
Intel already sent another new fix the original issue:
https://patchwork.freedesktop.org/series/105573/

> So how can we trust any HWE submission that says cherry pick in the future?
> What does the revert in Jammy _actually_ do? Both patches are completely different, so is Jammy really affected by the issues which the upstream patch caused?

The revert is trying to be back to  540000 instead of 810000 on all ADL+ platform.

The cherry-pick patch did the same thing as the commit ID.
It looks like a backport and but no mention.

>
> The Jammy patch probably should be reverted under that commit message. The question is, should the code get re-applied again with the _CORRECT_ provenance?

No need to re-applied again this patch, new patch above is coming as a real fix.

Regards,
Aaron

>
> -Stefan