asahi: Use writeback when it looks beneficial

When playing the My Little Pony theme song at 1080p on T8103, with mpv's GPU
compositing but software decoding, CPU usage drops from 200% to 50% due to
proper caching of the staging resource.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21063>

diff --git a/src/gallium/drivers/asahi/agx_pipe.c b/src/gallium/drivers/asahi/agx_pipe.c
index 689b66f..3607ad3 100644 (file)
--- a/src/gallium/drivers/asahi/agx_pipe.c
+++ b/src/gallium/drivers/asahi/agx_pipe.c
@@ -530,7 +530,19 @@ agx_resource_create_with_modifiers(struct pipe_screen *screen,
                        : (bind & PIPE_BIND_SHADER_IMAGE)    ? "Shader image"
                                                             : "Other resource";
 
-   nresource->bo = agx_bo_create(dev, nresource->layout.size_B, 0, label);
+   uint32_t create_flags = 0;
+
+   /* Default to write-combine resources, but use writeback if that is expected
+    * to be beneficial.
+    */
+   if (nresource->base.usage == PIPE_USAGE_STAGING ||
+       (nresource->base.flags & PIPE_RESOURCE_FLAG_MAP_COHERENT)) {
+
+      create_flags |= AGX_BO_WRITEBACK;
+   }
+
+   nresource->bo =
+      agx_bo_create(dev, nresource->layout.size_B, create_flags, label);
 
    if (!nresource->bo) {
       FREE(nresource);