[Intel-gfx] [PATCH 4.19 36/39] drm/i915: Dont use BAR mappings for ring buffers with LLC

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

commit 85636167e3206c3fbd52254fc432991cc4e90194 upstream.

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>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/gpu/drm/i915/intel_ringbuffer.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1083,7 +1083,7 @@ int intel_ring_pin(struct intel_ring *ri
 	if (unlikely(ret))
 		return ret;
 
-	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, map);
@@ -1118,7 +1118,7 @@ void intel_ring_unpin(struct intel_ring
 	/* Discard any unused bytes beyond that submitted to hw. */
 	intel_ring_reset(ring, ring->tail);
 
-	if (i915_vma_is_map_and_fenceable(ring->vma))
+	if (i915_vma_is_map_and_fenceable(ring->vma) && !HAS_LLC(ring->vma->vm->i915))
 		i915_vma_unpin_iomap(ring->vma);
 	else
 		i915_gem_object_unpin_map(ring->vma->obj);