[Intel-gfx] [PATCH 6/6] drm/i915/gt: Serialize TLB invalidates with GT resets

[Mauro Carvalho Chehab]

From: Chris Wilson <chris.p.wilson at intel.com>

Avoid trying to invalidate the TLB in the middle of performing an
engine reset, as this may result in the reset timing out. Currently,
the TLB invalidate is only serialised by its own mutex, forgoing the
uncore lock, but we can take the uncore->lock as well to serialise
the mmio access, thereby serialising with the GDRST.

Tested on a NUC5i7RYB, BIOS RYBDWi35.86A.0380.2019.0517.1530 with
i915 selftest/hangcheck.

Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")

Reported-by: Mauro Carvalho Chehab <mchehab at kernel.org>
Tested-by: Mauro Carvalho Chehab <mchehab at kernel.org>
Reviewed-by: Mauro Carvalho Chehab <mchehab at kernel.org>
Signed-off-by: Chris Wilson <chris.p.wilson at intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
Cc: stable at vger.kernel.org
Acked-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab at kernel.org>
---

See [PATCH 0/6] at: https://lore.kernel.org/all/cover.1655306128.git.mchehab@kernel.org/

 drivers/gpu/drm/i915/gt/intel_gt.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
index fb4fd5273ca4..33eb93586858 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt.c
@@ -1248,6 +1248,8 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
 	mutex_lock(&gt->tlb_invalidate_lock);
 	intel_uncore_forcewake_get(uncore, FORCEWAKE_ALL);
 
+	spin_lock_irq(&uncore->lock); /* seralise invalidate with GT reset */
+
 	awake = 0;
 	for_each_engine(engine, gt, id) {
 		struct reg_and_bit rb;
@@ -1272,6 +1274,8 @@ void intel_gt_invalidate_tlbs(struct intel_gt *gt)
 	     IS_ALDERLAKE_P(i915)))
 		intel_uncore_write_fw(uncore, GEN12_OA_TLB_INV_CR, 1);
 
+	spin_unlock_irq(&uncore->lock);
+
 	for_each_engine_masked(engine, gt, awake, tmp) {
 		struct reg_and_bit rb;
 
-- 
2.36.1