drm/i915: Don't use BAR mappings for ring buffers with LLC

commit 3bb9bb4c3a581e589c40267297dfd6cf53e28848 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: a9ab7be3b7ce ("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 bf1c6775058a1ed4d27cedbb5ed4a0803b3302a5)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/gt/intel_ring.c b/drivers/gpu/drm/i915/gt/intel_ring.c
index fb1d2595392ede154c55399de06f2b082a186faa..fb99143be98e7327af823de10635563bccaca566 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_ring.c
+++ b/drivers/gpu/drm/i915/gt/intel_ring.c
@@ -53,7 +53,7 @@ int intel_ring_pin(struct intel_ring *ring, struct i915_gem_ww_ctx *ww)
        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 {
                int type = i915_coherent_map_type(vma->vm->i915, vma->obj, false);
@@ -98,7 +98,7 @@ void intel_ring_unpin(struct intel_ring *ring)
                return;
 
        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);