NACK/Cmnt: [PATCH 00/18][SRU][G][HWE-5.8] Fix compatibility issue on some external monitors

[Stefan Bader]

On 08.04.21 07:56, Stefan Bader wrote:
> On 23.03.21 09:27, Stefan Bader wrote:
>> On 22.03.21 16:47, Aaron Ma wrote:
>>> BugLink: https://bugs.launchpad.net/bugs/1920777
>>>
>>> [Impact]
>>> Some external monitors got black screen via HDMI on laptops with Intel
>>> GPU.
>>>
>>> [Fix]
>>> Reading more of the port caps and dealing with various clock/bpc
>>> limitations.
>>> Patchset:
>>> https://patchwork.freedesktop.org/series/72928/
>>>
>>> [Test Case]
>>> Verified on the target platform and other 2 laptops include workstation,
>>> Tested on LG/ThinkVision 4k monitors and Dell 1080p monitor, include
>>> dock station.
>>> All good.
>>>
>>> [Where problems could occur]
>>> Intel GPU may lose or mess the output.
>>>
>>> These patches are most backported from 5.10-rc1 and one from 5.11-rc5.
>>> Hirsute/Unstable already got them.
>>>
>>> Ville Syrjälä (18):
>>>    drm/i915/lspcon: Do not send infoframes to non-HDMI sinks
>>>    drm/dp: Define protocol converter DPCD registers
>>>    drm/dp: Define more downstream facing port caps
>>>    drm/i915: Reworkd DFP max bpc handling
>>>    drm/dp: Add helpers to identify downstream facing port types
>>>    drm/dp: Pimp drm_dp_downstream_max_bpc()
>>>    drm/dp: Redo drm_dp_downstream_max_clock() as
>>>      drm_dp_downstream_max_dotclock()
>>>    drm/i915: Reworkd DP DFP clock handling
>>>    drm/dp: Add drm_dp_downstream_{min,max}_tmds_clock()
>>>    drm/i915: Deal with TMDS DFP clock limits
>>>    drm/i915: Configure DP 1.3+ protocol converted HDMI mode
>>>    drm/dp: Add drm_dp_downstream_mode()
>>>    drm/i915: Handle downstream facing ports w/o EDID
>>>    drm/i915: Extract intel_hdmi_has_audio()
>>>    drm/i915: DP->HDMI TMDS clock limits vs. deep color
>>>    drm/dp: Add helpers for DFP YCbCr 4:2:0 handling
>>>    drm/i915: Do YCbCr 444->420 conversion via DP protocol converters
>>>    drm/i915: Only enable DFP 4:4:4->4:2:0 conversion when outputting
>>>      YCbCr 4:4:4
>>>
>>>   drivers/gpu/drm/drm_dp_helper.c               | 381 ++++++++++++++++--
>>>   drivers/gpu/drm/drm_edid.c                    |  28 ++
>>>   drivers/gpu/drm/i915/display/intel_ddi.c      |  11 +-
>>>   .../drm/i915/display/intel_display_debugfs.c  |   3 +-
>>>   .../drm/i915/display/intel_display_types.h    |   9 +
>>>   drivers/gpu/drm/i915/display/intel_dp.c       | 305 +++++++++++---
>>>   drivers/gpu/drm/i915/display/intel_dp.h       |   2 +
>>>   drivers/gpu/drm/i915/display/intel_hdmi.c     |  82 ++--
>>>   drivers/gpu/drm/i915/display/intel_hdmi.h     |   2 +
>>>   include/drm/drm_dp_helper.h                   |  63 ++-
>>>   include/drm/drm_edid.h                        |   4 +
>>>   11 files changed, 758 insertions(+), 132 deletions(-)
>>>
>> First why is this explicitly targeted to focal:linux-hwe-5.8 when also asked 
>> to be applied to groovy:linux? Hwe kernels are and always have been backports 
>> from the respective series primary kernel.
>> Second, is this really the minimal set required to fix the problems? This 
>> looks more to be a partial rework and for that testing only on 3 machines 
>> (which does not say anything about which generations of Intel graphics get 
>> covered). For a change that huge I would rather expect to cover the whole 
>> range of generations we still have around.
>> The patches seem to origin from 5.10..5.11 which means the broadest range of 
>> testing would not happen before Hirsute does release. Before that I am rather 
>> suspicious the bigger the change set becomes.
>>
>> -Stefan
>>
>>
> There has not been any update on this and this still is a rather extensive set. 
> Bug fixes should try to be as small as possible because the bigger the change 
> the greater the risk to cause some unforeseen problems.
> In some cases this maybe is not possible. But then this should be explained in 
> more detail and also testing should be at a wider range. Especially with i915 
> which has been breaking older generations of the GPU.
> In this case it seems the better option is to wait for the hirsute/5.11 kernel 
> to replace the groovy/5.8 one as focal hwe kernel.
> 
> -Stefan
> 
> 
PS: Generally, if a set really needs to consist of more than ~5 patches, it 
would be preferable to have a pull request at least embedded in the cover email 
(or just a pull request style submission overall).


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