[PATCH v5 3/6] drm/i915: ttm move/clear logic fix

[Robert Beckett <bob.beckett@collabora.com>]

ttm managed buffers start off with system resource definitions and ttm_tt
tracking structures allocated (though unpopulated).
currently this prevents clearing of buffers on first move to desired
placements.

The desired behaviour is to clear user allocated buffers and any kernel
buffers that specifically requests it only.
Make the logic match the desired behaviour.

Signed-off-by: Robert Beckett <bob.beckett@collabora.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c | 22 +++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
index 48046cfd8c4b..2895e13a1cac 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
@@ -3,6 +3,7 @@
  * Copyright © 2021 Intel Corporation
  */
 
+#include "drm/ttm/ttm_tt.h"
 #include <drm/ttm/ttm_bo_driver.h>
 
 #include "i915_deps.h"
@@ -471,6 +472,25 @@ __i915_ttm_move(struct ttm_buffer_object *bo,
 	return fence;
 }
 
+static bool
+allow_clear(struct drm_i915_gem_object *obj, struct ttm_tt *ttm, struct ttm_resource *dst_mem)
+{
+	/* never clear stolen */
+	if (dst_mem->mem_type == I915_PL_STOLEN)
+		return false;
+	/*
+	 * we want to clear user buffers and any kernel buffers
+	 * that specifically request clearing.
+	 */
+	if (obj->flags & I915_BO_ALLOC_USER)
+		return true;
+
+	if (ttm && ttm->page_flags & TTM_TT_FLAG_ZERO_ALLOC)
+		return true;
+
+	return false;
+}
+
 /**
  * i915_ttm_move - The TTM move callback used by i915.
  * @bo: The buffer object.
@@ -521,7 +541,7 @@ int i915_ttm_move(struct ttm_buffer_object *bo, bool evict,
 		return PTR_ERR(dst_rsgt);
 
 	clear = !i915_ttm_cpu_maps_iomem(bo->resource) && (!ttm || !ttm_tt_is_populated(ttm));
-	if (!(clear && ttm && !(ttm->page_flags & TTM_TT_FLAG_ZERO_ALLOC))) {
+	if (!clear || allow_clear(obj, ttm, dst_mem)) {
 		struct i915_deps deps;
 
 		i915_deps_init(&deps, GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
-- 
2.25.1