drm/amdgpu: Move to gtt before cpu accesses dma buf.

To improve cpu read performance. This is implemented for APUs currently.

v2: Adapt to change https://lists.freedesktop.org/archives/amd-gfx/2017-October/015174.html
v3: Adapt to change "forward begin_cpu_access callback to drivers"
v4: Instead of v3, reuse drm_gem dmabuf_ops here. Also some minor fixes as suggested.
v5: only set dma_buf ops when it is valid (Samuel)

Signed-off-by: Samuel Li <Samuel.Li@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 69 insertions, 1 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
index ae9c106979d7..8afec21dc45d 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
@@ -26,6 +26,7 @@
 #include <drm/drmP.h>
 
 #include "amdgpu.h"
+#include "amdgpu_display.h"
 #include <drm/amdgpu_drm.h>
 #include <linux/dma-buf.h>
 
@@ -164,6 +165,50 @@ struct reservation_object *amdgpu_gem_prime_res_obj(struct drm_gem_object *obj)
         return bo->tbo.resv;
 }
 
+static int amdgpu_gem_begin_cpu_access(struct dma_buf *dma_buf,
+                                       enum dma_data_direction direction)
+{
+        struct amdgpu_bo *bo = gem_to_amdgpu_bo(dma_buf->priv);
+        struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
+        struct ttm_operation_ctx ctx = { true, false };
+        u32 domain = amdgpu_display_framebuffer_domains(adev);
+        int ret;
+        bool reads = (direction == DMA_BIDIRECTIONAL ||
+                      direction == DMA_FROM_DEVICE);
+
+        if (!reads || !(domain & AMDGPU_GEM_DOMAIN_GTT))
+                return 0;
+
+        /* move to gtt */
+        ret = amdgpu_bo_reserve(bo, false);
+        if (unlikely(ret != 0))
+                return ret;
+
+        if (!bo->pin_count && (bo->allowed_domains & AMDGPU_GEM_DOMAIN_GTT)) {
+                amdgpu_ttm_placement_from_domain(bo, AMDGPU_GEM_DOMAIN_GTT);
+                ret = ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
+        }
+
+        amdgpu_bo_unreserve(bo);
+        return ret;
+}
+
+static const struct dma_buf_ops amdgpu_dmabuf_ops = {
+        .attach = drm_gem_map_attach,
+        .detach = drm_gem_map_detach,
+        .map_dma_buf = drm_gem_map_dma_buf,
+        .unmap_dma_buf = drm_gem_unmap_dma_buf,
+        .release = drm_gem_dmabuf_release,
+        .begin_cpu_access = amdgpu_gem_begin_cpu_access,
+        .map = drm_gem_dmabuf_kmap,
+        .map_atomic = drm_gem_dmabuf_kmap_atomic,
+        .unmap = drm_gem_dmabuf_kunmap,
+        .unmap_atomic = drm_gem_dmabuf_kunmap_atomic,
+        .mmap = drm_gem_dmabuf_mmap,
+        .vmap = drm_gem_dmabuf_vmap,
+        .vunmap = drm_gem_dmabuf_vunmap,
+};
+
 struct dma_buf *amdgpu_gem_prime_export(struct drm_device *dev,
                                         struct drm_gem_object *gobj,
                                         int flags)
@@ -176,7 +221,30 @@ struct dma_buf *amdgpu_gem_prime_export(struct drm_device *dev,
                 return ERR_PTR(-EPERM);
 
         buf = drm_gem_prime_export(dev, gobj, flags);
-        if (!IS_ERR(buf))
+        if (!IS_ERR(buf)) {
                 buf->file->f_mapping = dev->anon_inode->i_mapping;
+                buf->ops = &amdgpu_dmabuf_ops;
+        }
+
         return buf;
 }
+
+struct drm_gem_object *amdgpu_gem_prime_import(struct drm_device *dev,
+                                            struct dma_buf *dma_buf)
+{
+        struct drm_gem_object *obj;
+
+        if (dma_buf->ops == &amdgpu_dmabuf_ops) {
+                obj = dma_buf->priv;
+                if (obj->dev == dev) {
+                        /*
+                         * Importing dmabuf exported from out own gem increases
+                         * refcount on gem itself instead of f_count of dmabuf.
+                         */
+                        drm_gem_object_get(obj);
+                        return obj;
+                }
+        }
+
+        return drm_gem_prime_import(dev, dma_buf);
+}