[SRU][OEM-5.10][PATCH 0/2] Display abnormal on the TGL+4k panel machines

[Hui Wang]

BugLink: https://bugs.launchpad.net/bugs/1922885

This SRU is only for oem-5.10 temporarily, there are 2 patches in this
SRU, the 1st patch is for applying the 2nd patch without conflict, and
the 2nd patch is the key to fix this issue. But the 2nd patch is just
a workaround from Intel, it is not a real fix, it just disable the
DC3 clock off support for all TGL psr2 unconditionally, so I only send
the patches to oem-5.10 kernel since the LENOVO has been pushing us to
fix the oem bug for long time.

After Intel has real solution of this issue, will revert the patches
and send the real solution patches to all ubuntu kernels.

[Impact]
On the TGL machines, if the panel is 4k resolution and the i915 driver
is in PSR2 mode, the display will be abnormal randomly and the
keyboard reponse is delayed randomly.

[Fix]
We reported this issue to Intel and Lenovo shipped a machine to Intel
developer, they reproduced the issue and they provided a workaroud
patch.

[Test]
Booting the system with patched kernel, open 10+ terminal windows,
move those windows or resize those windows for 10 mins, the display
is good. Open a terminal and press 1, 2, 3 and 4 keys rapidly and
repeatedly, the 1, 2, 3, 4 is showed on the terminal immediately,
there is no delay between pressing and showing.


[Where problems could occur]
After applying these patches, the DC3 clock off mode is disabled
unconditionally on the TGL+PSR2 machines, this could introduce
power consumption regression. But we tested the patched kernel on
different TGL lenovo machines, all power_management test cases passed.



Gwan-gyeong Mun (2):
  drm/i915/display: Do not allow DC3CO if PSR SF is enabled
  UBUNTU: SAUCE: drm/i915/display/psr: Disable DC3CO when the PSR2 is
    used

 drivers/gpu/drm/i915/display/intel_psr.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

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2.25.1