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

This reverts commit 4eb6789 which is
commit 8563616 upstream.

It has been reported to cause problems on Alpine Linux and Manjaro Linux
5.15-based releases, so revert it for now until it can be sorted out.

Reported-by: "A.P. Jo." <apjo@tuta.io>
Link: https://lore.kernel.org/r/NQJqG8n--3-9@tuta.io
Link: https://gitlab.alpinelinux.org/alpine/aports/-/issues/14704
Reported-by: Philip Müller <philm@manjaro.org>
Link: https://lore.kernel.org/r/d955327b-cb1c-4646-76b9-b0499c0c64c6@manjaro.org
Link: https://gitlab.freedesktop.org/drm/intel/-/issues/8284
Cc: John Harrison <John.C.Harrison@Intel.com>
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+
Cc: Jouni Högander <jouni.hogander@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/i915/gt/intel_ring.c

@@ -51,7 +51,7 @@ 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) && !HAS_LLC(vma->vm->i915)) {
+	if (i915_vma_is_map_and_fenceable(vma)) {
 		addr = (void __force *)i915_vma_pin_iomap(vma);
 	} else {
 		int type = i915_coherent_map_type(vma->vm->i915, vma->obj, false);
@@ -96,7 +96,7 @@ void intel_ring_unpin(struct intel_ring *ring)
 		return;
 
 	i915_vma_unset_ggtt_write(vma);
-	if (i915_vma_is_map_and_fenceable(vma) && !HAS_LLC(vma->vm->i915))
+	if (i915_vma_is_map_and_fenceable(vma))
 		i915_vma_unpin_iomap(vma);
 	else
 		i915_gem_object_unpin_map(vma->obj);