[PATCH 5.4.y] drm/i915: Don't use BAR mappings for ring buffers with LLC

[John.C.Harrison@Intel.com]

From: John Harrison <John.C.Harrison@Intel.com>

Direction from hardware is that ring buffers should never be mapped
via the BAR on systems with LLC. There are too many caching pitfalls
due to the way BAR accesses are routed. So it is safest to just not
use it.

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Fixes: 9d80841ea4c9 ("drm/i915: Allow ringbuffers to be bound anywhere")
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v4.9+
Tested-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230216011101.1909009-3-John.C.Harrison@Intel.com
(cherry picked from commit 65c08339db1ada87afd6cfe7db8e60bb4851d919)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
(cherry picked from commit 85636167e3206c3fbd52254fc432991cc4e90194)
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
---
 drivers/gpu/drm/i915/gt/intel_ringbuffer.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_ringbuffer.c b/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
index eee9fcbe0434..808269b2108f 100644
--- a/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
@@ -1208,7 +1208,7 @@ int intel_ring_pin(struct intel_ring *ring)
 	if (unlikely(ret))
 		goto err_unpin;
 
-	if (i915_vma_is_map_and_fenceable(vma))
+	if (i915_vma_is_map_and_fenceable(vma) && !HAS_LLC(vma->vm->i915))
 		addr = (void __force *)i915_vma_pin_iomap(vma);
 	else
 		addr = i915_gem_object_pin_map(vma->obj,
@@ -1252,7 +1252,7 @@ void intel_ring_unpin(struct intel_ring *ring)
 	intel_ring_reset(ring, ring->emit);
 
 	i915_vma_unset_ggtt_write(vma);
-	if (i915_vma_is_map_and_fenceable(vma))
+	if (i915_vma_is_map_and_fenceable(vma) && !HAS_LLC(vma->vm->i915))
 		i915_vma_unpin_iomap(vma);
 	else
 		i915_gem_object_unpin_map(vma->obj);
-- 
2.39.1