Chris Wilson 4055dc75d6 drm/i915: Stop touching forcewake following a gen6+ engine reset ... Forcewake is not affected by the engine reset on gen6+. Indeed the reason why we added intel_uncore_forcewake_reset() to gen6_reset_engines() was to keep the bookkeeping intact because the reset did not touch the forcewake bit (yet we cancelled the forcewake consumers)! This was done in commit 521198a2e7: Author: Mika Kuoppala <mika.kuoppala@linux.intel.com> Date: Fri Aug 23 16:52:30 2013 +0300 drm/i915: sanitize forcewake registers on reset In reset we try to restore the forcewake state to pre reset state, using forcewake_count. The reset doesn't seem to clear the forcewake bits so we get warn on forcewake ack register not clearing. That futzing of the forcewake bookkeeping was dropped in commit 0294ae7b44 ("drm/i915: Consolidate forcewake resetting to a single function"), but it did not make the realisation that the remaining intel_uncore_forcewake_reset() was redundant. The new danger with using intel_uncore_forcewake_reset() with per-engine resets is that the driver and hw are still in an active state as we perform the reset. We may be using the forcewake to read protected registers elsewhere and those results may be clobbered by the concurrent dropping of forcewake. Reported-by: Michel Thierry <michel.thierry@intel.com> Fixes: 142bc7d99b ("drm/i915: Modify error handler for per engine hang recovery") Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> Cc: Michel Thierry <michel.thierry@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20170817173229.20324-1-chris@chris-wilson.co.uk Reviewed-by: Michel Thierry <michel.thierry@intel.com> Acked-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>		2017-08-18 10:05:59 +01:00
..
drm	drm/i915: Stop touching forcewake following a gen6+ engine reset	2017-08-18 10:05:59 +01:00
host1x	gpu/host1x: Remove excess parameter in host1x_subdev_add docs	2017-07-31 14:24:37 +02:00
ipu-v3	drm: Convert to using %pOF instead of full_name	2017-07-26 13:45:06 +02:00
vga	sched/wait: Rename wait_queue_t => wait_queue_entry_t	2017-06-20 12:18:27 +02:00
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