[Mesa-dev] [PATCH 1/2] r600g/radeonsi: Reduce or even drop special treatment of persistent mappings

[Michel Dänzer]

From: Michel Dänzer <michel.daenzer at amd.com>

Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>
---
 src/gallium/drivers/radeon/r600_buffer_common.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/gallium/drivers/radeon/r600_buffer_common.c b/src/gallium/drivers/radeon/r600_buffer_common.c
index 4e6b897..154c33d 100644
--- a/src/gallium/drivers/radeon/r600_buffer_common.c
+++ b/src/gallium/drivers/radeon/r600_buffer_common.c
@@ -127,13 +127,17 @@ bool r600_init_resource(struct r600_common_screen *rscreen,
 		break;
 	}
 
-	/* Use GTT for all persistent mappings, because they are
-	 * always cached and coherent. */
-	if (res->b.b.target == PIPE_BUFFER &&
+	/* Use GTT for all persistent mappings with older kernels, because they
+	 * didn't always flush the HDP cache before CS execution.
+	 *
+	 * Write-combined CPU mappings are fine, the kernel ensures all CPU
+	 * writes finish before the GPU executes a command stream.
+	 */
+	if (rscreen->info.drm_minor < 40 &&
+	    res->b.b.target == PIPE_BUFFER &&
 	    res->b.b.flags & (PIPE_RESOURCE_FLAG_MAP_PERSISTENT |
 			      PIPE_RESOURCE_FLAG_MAP_COHERENT)) {
 		res->domains = RADEON_DOMAIN_GTT;
-		flags = 0;
 	}
 
 	/* Tiled textures are unmappable. Always put them in VRAM. */
-- 
2.0.1