We are seeing "DMAR faults [reason 7, next page table ptr is invalid]"
on TGL while running suspend stress test. Refer to 'commit 84361529ee85
("drm/i915: Sleep around performing iommu unmaps on Tigerlake")'.
Driver check needs_idle_maps() in i915_gmch_probe() but it applicable
for gen5 and earlier generations. Add needs_idle_maps() in gen8_gmch_probe()
then it will benifit gen8 and later platform.

Cc: Chris Wilson <[email protected]>
Cc: Mika Kuoppala <[email protected]>
Cc: Ville Syrjala <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Cooper Chiou <[email protected]>
Cc: Huang Derek <[email protected]>
Signed-off-by: Lee Shawn C <[email protected]>
---
 drivers/gpu/drm/i915/gt/intel_ggtt.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt.c 
b/drivers/gpu/drm/i915/gt/intel_ggtt.c
index de3ac58fceec..9510da0ae6b5 100644
--- a/drivers/gpu/drm/i915/gt/intel_ggtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_ggtt.c
@@ -911,6 +911,12 @@ static int gen8_gmch_probe(struct i915_ggtt *ggtt)
 
        ggtt->vm.alloc_pt_dma = alloc_pt_dma;
 
+       if (needs_idle_maps(i915)) {
+               drm_notice(&i915->drm,
+                          "Flushing DMA requests before IOMMU unmaps; 
performance may be degraded\n");
+               ggtt->do_idle_maps = true;
+       }
+
        ggtt->vm.total = (size / sizeof(gen8_pte_t)) * I915_GTT_PAGE_SIZE;
        ggtt->vm.cleanup = gen6_gmch_remove;
        ggtt->vm.insert_page = gen8_ggtt_insert_page;
-- 
2.17.1

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