[Intel-gfx] [PATCH 2/7] drm/i915: Introduce per-engine workarounds

[Chris Wilson]

Quoting Tvrtko Ursulin (2018-11-30 17:44:07)
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> We stopped re-applying the GT workarounds after engine reset since commit
> 59b449d5c82a ("drm/i915: Split out functions for different kinds of
> workarounds").
> 
> Issue with this is that some of the GT workarounds live in the MMIO space
> which gets lost during engine resets. So far the registers in 0x2xxx and
> 0xbxxx address range have been identified to be affected.
> 
> This losing of applied workarounds has obvious negative effects and can
> even lead to hard system hangs (see the linked Bugzilla).
> 
> Rather than just restoring this re-application, because we have also
> observed that it is not safe to just re-write all GT workarounds after
> engine resets (GPU might be live and weird hardware states can happen),
> we introduce a new class of per-engine workarounds and move only the
> affected GT workarounds over.
> 
> Using the framework introduced in the previous patch, we therefore after
> engine reset, re-apply only the workarounds living in the affected MMIO
> address ranges.
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Bugzilla: https://bugzilla.freedesktop.org/show_bug.cgi?id=107945
> Fixes: 59b449d5c82a ("drm/i915: Split out functions for different kinds of workarounds")
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Jani Nikula <jani.nikula at linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Cc: intel-gfx at lists.freedesktop.org

Give or take the naming arguments,
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris