[Intel-gfx] [PATCH] drm/i915/gt: Scrub HW state on remove

[Chris Wilson]

Currently we do a final scrub of the HW state upon release. However,
when rebinding the device, this is too late as the device may either
have been partially rebound or the device is no longer accessible. If
the device has been removed before release, the reset goes astray
leaving the device in an inconsistent state, unlikely to work without a
full PCI reset. Furthermore, if the device is partially rebound before
the HW scrubbing, there may be leftover HW state that should have been
scrubbed. Either way, we need to push the scrubbing earlier before the
removal, so into unregister. The danger is that on older machines,
reseting the GPU also impact the display engine and so the reset should
be after modesetting is disabled (and before reuse we need to recover
modesetting).

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2508
Testcase: igt/core_hotunplug
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gt/intel_gt.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
index 39b428c5049c..44f1d51e5ae5 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt.c
@@ -614,6 +614,8 @@ void intel_gt_driver_remove(struct intel_gt *gt)
 
 void intel_gt_driver_unregister(struct intel_gt *gt)
 {
+	intel_wakeref_t wakeref;
+
 	intel_rps_driver_unregister(&gt->rps);
 
 	/*
@@ -622,16 +624,15 @@ void intel_gt_driver_unregister(struct intel_gt *gt)
 	 * resources.
 	 */
 	intel_gt_set_wedged(gt);
+
+	/* Scrub all HW state upon release */
+	with_intel_runtime_pm(gt->uncore->rpm, wakeref)
+		__intel_gt_reset(gt, ALL_ENGINES);
 }
 
 void intel_gt_driver_release(struct intel_gt *gt)
 {
 	struct i915_address_space *vm;
-	intel_wakeref_t wakeref;
-
-	/* Scrub all HW state upon release */
-	with_intel_runtime_pm(gt->uncore->rpm, wakeref)
-		__intel_gt_reset(gt, ALL_ENGINES);
 
 	vm = fetch_and_zero(&gt->vm);
 	if (vm) /* FIXME being called twice on error paths :( */
-- 
2.20.1