NACK: [SRU][F][PATCH 0/1] drm/i915: Skip some timing checks on BXT/GLK DSI transcoders

[Manuel Diewald]

On Fri, Dec 15, 2023 at 05:02:14PM +0100, Dariusz Gadomski wrote:
> BugLink: https://bugs.launchpad.net/bugs/2044131
> 
> [ Impact ]
> Commit 8f4b1068e7fc3df1a77ac8151767e56b208cc87f introduced some timing checks
> which have been proven invalid for at least some hardware setups.  A user trying
> to run Focal with HWE 5.15 kernel is not able to get any video output.  After
> going through bisection between 5.4 and 5.5 this commit was identified.
> Reverting it on top of Focal HWE kernel fixes the issue.
> 
> The issue has also been addressed upstream in DRM tree
> (20c2dbff342aec13bf93c2f6c951da198916a455) and has been merge into linux-next
> (e0ef2daa8ca8ce4dbc2fd0959e383b753a87fd7d).
> 
> dmesg and lspci from the affected configuration are attached to this bug.
> 
> [ Test Plan ]
> 1. Boot the affected hardware with Ubuntu desktop running kernel v5.5 or higher.
> 2. Wait until boot finishes and see the blank screen.
> 
> Actual result: there is no video output visible.  Expected result: normal boot
> process should be visible (e.g. splash), then GUI should appear.
> 
> [ Where problem could occur ]
> This bug was a result of assumptions in the checks that turned out to be not
> valid for some hardware. The checks were removed from global intel_mode_valid
> function and moved into connector specific .mode_valid() hooks, entirely skiping
> BXT/GLK DSI connectors.
> 
> This should keep the checks where appropriate and skip for hardware that does
> not comply to them.
> 
> Ville Syrjälä (1):
>   drm/i915: Skip some timing checks on BXT/GLK DSI transcoders
> 
>  drivers/gpu/drm/i915/display/icl_dsi.c       |  7 +++++++
>  drivers/gpu/drm/i915/display/intel_crt.c     |  5 +++++
>  drivers/gpu/drm/i915/display/intel_display.c | 10 ++++++++++
>  drivers/gpu/drm/i915/display/intel_display.h |  3 +++
>  drivers/gpu/drm/i915/display/intel_dp.c      |  4 ++++
>  drivers/gpu/drm/i915/display/intel_dp_mst.c  |  4 ++++
>  drivers/gpu/drm/i915/display/intel_dvo.c     | 16 +++++++++++-----
>  drivers/gpu/drm/i915/display/intel_hdmi.c    |  4 ++++
>  drivers/gpu/drm/i915/display/intel_lvds.c    |  8 +++++++-
>  drivers/gpu/drm/i915/display/intel_sdvo.c    |  8 +++++++-
>  drivers/gpu/drm/i915/display/intel_tv.c      |  8 +++++++-
>  drivers/gpu/drm/i915/display/vlv_dsi.c       | 18 +++++++++++++++++-
>  12 files changed, 86 insertions(+), 9 deletions(-)
> 
> -- 
> 2.34.1
> 
> 
> -- 
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Please include the BugLink not just in the cover letter but also in the
patch comment.

-- 
 Manuel