[Mesa-dev] [PATCH] r600: increase performance for DRI PRIME offloading if 2nd GPU is Evergreen+

[Mario Kleiner]

This is a direct port of Marek Olšáks patch
"radeonsi: increase performance for DRI PRIME
offloading if 2nd GPU is CIK or VI" to r600.

It uses SDMA for the detiling blit from renderoffload VRAM
to GTT, as SDMA is much faster for tiled->linear blits from
VRAM to GTT.

Testing on a dual Radeon HD-5770 setup reduced the time
for the render offload gpu to get its rendering into
system RAM from approximately 16 msecs for simple rendering
at 1920x1080 pixel 32 bpp to 5 msecs, a > 3x speedup!

This was measured using ftrace to trace the time the radeon kms
driver waited on the dmabuf fence of the renderoffload gpu to
complete.

All in all this brought the time for a flip down from 20 msecs
to 9 msecs, so the prime setup can display at full 60 fps instead
of barely 30 fps vsync'ed.

The current r600 implementation supports SDMA on Evergreen and
later, but not R600/R700 due to some bugs apparently present
in their SDMA implementation.

Signed-off-by: Mario Kleiner <mario.kleiner.de at gmail.com>
Cc: Marek Olšák <marek.olsak at amd.com>
---
 src/gallium/drivers/r600/r600_blit.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/src/gallium/drivers/r600/r600_blit.c b/src/gallium/drivers/r600/r600_blit.c
index adf616e..8fdc51c 100644
--- a/src/gallium/drivers/r600/r600_blit.c
+++ b/src/gallium/drivers/r600/r600_blit.c
@@ -850,11 +850,30 @@ static void r600_blit(struct pipe_context *ctx,
                       const struct pipe_blit_info *info)
 {
 	struct r600_context *rctx = (struct r600_context*)ctx;
+	struct r600_texture *rdst = (struct r600_texture *)info->dst.resource;
 
 	if (do_hardware_msaa_resolve(ctx, info)) {
 		return;
 	}
 
+	/* Using SDMA for copying to a linear texture in GTT is much faster.
+	 * This improves DRI PRIME performance.
+	 *
+	 * resource_copy_region can't do this yet, because dma_copy calls it
+	 * on failure (recursion).
+	 */
+	if (rdst->surface.level[info->dst.level].mode ==
+	    RADEON_SURF_MODE_LINEAR_ALIGNED &&
+	    rctx->b.dma_copy &&
+	    util_can_blit_via_copy_region(info, false)) {
+		rctx->b.dma_copy(ctx, info->dst.resource, info->dst.level,
+				 info->dst.box.x, info->dst.box.y,
+				 info->dst.box.z,
+				 info->src.resource, info->src.level,
+				 &info->src.box);
+		return;
+	}
+
 	assert(util_blitter_is_blit_supported(rctx->blitter, info));
 
 	/* The driver doesn't decompress resources automatically while
-- 
2.7.4