This flag allows userspace to give the kernel a hint that it should use
a non-snooped resource. To guarantee coherency at all times mappings
into userspace are done write combined, so userspace should avoid
reading back from those resources.
Signed-off-by: Lucas Stach <dev@xxxxxxxxxx>
---
On x86 an optimized userspace can save up on snoop traffic in the
system, on ARM the benefits are potentially much larger, as we can save
the manual cache flush/invalidate.
---
drivers/gpu/drm/nouveau/nouveau_bo.c | 11 ++++++++++-
drivers/gpu/drm/nouveau/nouveau_bo.h | 1 +
include/uapi/drm/nouveau_drm.h | 1 +
3 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
index f4a2eb9..c5fcbcc 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bo.c
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
@@ -231,6 +231,12 @@ nouveau_bo_new(struct drm_device *dev, int size, int align,
nouveau_bo_fixup_align(nvbo, flags, &align, &size);
nvbo->bo.mem.num_pages = size >> PAGE_SHIFT;
+
+ if (tile_flags & NOUVEAU_GEM_TILE_WCUS)
+ nvbo->valid_caching = TTM_PL_FLAG_UNCACHED | TTM_PL_FLAG_WC;
+ else
+ nvbo->valid_caching = TTM_PL_MASK_CACHING;
+
nouveau_bo_placement_set(nvbo, flags, 0);
acc_size = ttm_bo_dma_acc_size(&drm->ttm.bdev, size,
@@ -292,7 +298,7 @@ void
nouveau_bo_placement_set(struct nouveau_bo *nvbo, uint32_t type, uint32_t busy)
{
struct ttm_placement *pl = &nvbo->placement;
- uint32_t flags = TTM_PL_MASK_CACHING |
+ uint32_t flags = nvbo->valid_caching |
(nvbo->pin_refcnt ? TTM_PL_FLAG_NO_EVICT : 0);
pl->placement = nvbo->placements;
@@ -1554,6 +1560,9 @@ nouveau_bo_vma_add(struct nouveau_bo *nvbo, struct nouveau_vm *vm,
if (nvbo->bo.mem.mem_type == TTM_PL_VRAM)
nouveau_vm_map(vma, nvbo->bo.mem.mm_node);
else if (nvbo->bo.mem.mem_type == TTM_PL_TT) {
+ if (!(nvbo->valid_caching & TTM_PL_FLAG_CACHED))
+ vma->access |= NV_MEM_ACCESS_NOSNOOP;
+
if (node->sg)
nouveau_vm_map_sg_table(vma, 0, size, node);
else
diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.h b/drivers/gpu/drm/nouveau/nouveau_bo.h
index 653dbbb..2ecf8b7 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bo.h
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.h
@@ -9,6 +9,7 @@ struct nouveau_bo {
struct ttm_buffer_object bo;
struct ttm_placement placement;
u32 valid_domains;
+ u32 valid_caching;
u32 placements[3];
u32 busy_placements[3];
struct ttm_bo_kmap_obj kmap;
diff --git a/include/uapi/drm/nouveau_drm.h b/include/uapi/drm/nouveau_drm.h
index 2a5769f..4948eee2 100644
--- a/include/uapi/drm/nouveau_drm.h
+++ b/include/uapi/drm/nouveau_drm.h
@@ -36,6 +36,7 @@
#define NOUVEAU_GEM_TILE_32BPP 0x00000002
#define NOUVEAU_GEM_TILE_ZETA 0x00000004
#define NOUVEAU_GEM_TILE_NONCONTIG 0x00000008
+#define NOUVEAU_GEM_TILE_WCUS 0x00000010 /* write-combined, unsnooped */
struct drm_nouveau_gem_info {
uint32_t handle;
--
1.8.3.1
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