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drm/i915: Perform full wedge on display reset

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We lost the proper display reset deadlock handling in
commit d59cf7bb73 ("drm/i915/display: Use dma_fence interfaces instead of i915_sw_fence").
Currently the only thing that eventually breaks the deadlock is the
10 second fence timeout, which is very slow.

I tried to essentially restore the previous mechanism via a custom
dma_fence in
https://lore.kernel.org/intel-gfx/20260408233458.22666-6-ville.syrjala@linux.intel.com/
but Christian didn't want it.

The ideal solution would be to allow the reset time modesets to proceed
ahead of any already queued atomic commits, but that is quite involved
since we need to be able to track the already committed (to the
hardware) atomic states in addition to the userspace queued atomic states.
Years ago I did implement something like that in
https://lore.kernel.org/intel-gfx/20170629134948.5614-1-ville.syrjala@linux.intel.com/
but Sima didn't want it.

In order to get rid of the dependency on the timeout, and make things
faster, let's just effectively revert the remainders of
commit 9db529aac9 ("drm/i915: More surgically unbreak the modeset vs reset deadlock").
The upside is that the reset is fast again, but the downside is that
we now do a full wedge on all display resets, which will also kill
innocent batches. But perhaps no one really cares since this is
currently only needed for old pre-g4x hardware. But if anyone has plans on
using eg. FLR as a backup GPU reset on new hardware then we probably need
to come up with something better...

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/20260903130116.19089-1-ville.syrjala@linux.intel.com
Acked-by: Jani Nikula <jani.nikula@intel.com>
This commit is contained in:
Ville Syrjälä 2026-09-03 16:01:16 +03:00
commit 3aef9c94c0
5 changed files with 1 additions and 22 deletions
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