Pinning lots of small buffer objects, such as cursors or sprites, to video
memory can lead to fragmentation, which is a problem for devices with only
a small amount of memory. As a result, framebuffer images might not get
pinned, even though there's enough space available overall.
The flag DRM_GEM_VRAM_PL_FLAG_TOPDOWN marks buffer objects to be pinned at
the high end of video memory. This leaves contiguous space available at
the memory's low end.
Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
---
drivers/gpu/drm/drm_gem_vram_helper.c | 14 ++++++++++----
include/drm/drm_gem_vram_helper.h | 1 +
2 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/drm_gem_vram_helper.c b/drivers/gpu/drm/drm_gem_vram_helper.c
index 49588de88959..91baf3f279f1 100644
--- a/drivers/gpu/drm/drm_gem_vram_helper.c
+++ b/drivers/gpu/drm/drm_gem_vram_helper.c
@@ -58,6 +58,7 @@ static void drm_gem_vram_placement(struct drm_gem_vram_object *gbo,
{
unsigned int i;
unsigned int c = 0;
+ u32 invariant_flags = pl_flag & TTM_PL_FLAG_TOPDOWN;
gbo->placement.placement = gbo->placements;
gbo->placement.busy_placement = gbo->placements;
@@ -65,15 +66,18 @@ static void drm_gem_vram_placement(struct drm_gem_vram_object *gbo,
if (pl_flag & TTM_PL_FLAG_VRAM)
gbo->placements[c++].flags = TTM_PL_FLAG_WC |
TTM_PL_FLAG_UNCACHED |
- TTM_PL_FLAG_VRAM;
+ TTM_PL_FLAG_VRAM |
+ invariant_flags;
if (pl_flag & TTM_PL_FLAG_SYSTEM)
gbo->placements[c++].flags = TTM_PL_MASK_CACHING |
- TTM_PL_FLAG_SYSTEM;
+ TTM_PL_FLAG_SYSTEM |
+ invariant_flags;
if (!c)
gbo->placements[c++].flags = TTM_PL_MASK_CACHING |
- TTM_PL_FLAG_SYSTEM;
+ TTM_PL_FLAG_SYSTEM |
+ invariant_flags;
gbo->placement.num_placement = c;
gbo->placement.num_busy_placement = c;
@@ -236,7 +240,9 @@ static int drm_gem_vram_pin_locked(struct drm_gem_vram_object *gbo,
* a memory region. A pinned buffer object has to be unpinned before
* it can be pinned to another region. If the pl_flag argument is 0,
* the buffer is pinned at its current location (video RAM or system
- * memory).
+ * memory). The modifier DRM_GEM_VRAM_PL_FLAG_TOPDOWN marks the buffer
+ * object to be pinned at the high end of the memory region. Set this
+ * flag to avoid memory fragmentation.
*
* Returns:
* 0 on success, or
diff --git a/include/drm/drm_gem_vram_helper.h b/include/drm/drm_gem_vram_helper.h
index 418eb1122861..354a9cd358a3 100644
--- a/include/drm/drm_gem_vram_helper.h
+++ b/include/drm/drm_gem_vram_helper.h
@@ -19,6 +19,7 @@ struct vm_area_struct;
#define DRM_GEM_VRAM_PL_FLAG_VRAM TTM_PL_FLAG_VRAM
#define DRM_GEM_VRAM_PL_FLAG_SYSTEM TTM_PL_FLAG_SYSTEM
+#define DRM_GEM_VRAM_PL_FLAG_TOPDOWN TTM_PL_FLAG_TOPDOWN
/*
* Buffer-object helpers
--
2.23.0
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