drm/i915: Stop dropping irq around resets

A long time ago, we were afraid of handling interrupts and signaling
waiters during a reset, worrying that the confusion in request handling
would interfere with our attempts to process the reset in an orderly
fashion. Since then, we have isolated our irq-driven request handling by
virtue of the engine->timeline.lock and control of kthreads where
required, eliminating the danger of concurrently processing interrupts.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180806145647.13131-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_drv.c

@@ -1918,7 +1918,6 @@ void i915_reset(struct drm_i915_private *i915,
 		dev_notice(i915->drm.dev, "Resetting chip for %s\n", reason);
 	error->reset_count++;
 
-	disable_irq(i915->drm.irq);
 	ret = i915_gem_reset_prepare(i915);
 	if (ret) {
 		dev_err(i915->drm.dev, "GPU recovery failed\n");
@@ -1980,8 +1979,6 @@ void i915_reset(struct drm_i915_private *i915,
 
 finish:
 	i915_gem_reset_finish(i915);
-	enable_irq(i915->drm.irq);
-
 wakeup:
 	clear_bit(I915_RESET_HANDOFF, &error->flags);
 	wake_up_bit(&error->flags, I915_RESET_HANDOFF);