drm/radeon/kms/evergreen: fix backend setup

This patch fixes rendering errors on some evergreen boards.
Hardcoding the backend map is not an optimal solution, but
a better fix is being worked on.

Similar to the fix for rv740
(6271901).

Fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=29986

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/evergreen.c

@@ -1160,14 +1160,25 @@ static void evergreen_gpu_init(struct radeon_device *rdev)
 									EVERGREEN_MAX_BACKENDS_MASK));
 			break;
 		}
-	} else
-		gb_backend_map =
-			evergreen_get_tile_pipe_to_backend_map(rdev,
-							       rdev->config.evergreen.max_tile_pipes,
-							       rdev->config.evergreen.max_backends,
-							       ((EVERGREEN_MAX_BACKENDS_MASK <<
-								 rdev->config.evergreen.max_backends) &
-								EVERGREEN_MAX_BACKENDS_MASK));
+	} else {
+		switch (rdev->family) {
+		case CHIP_CYPRESS:
+		case CHIP_HEMLOCK:
+			gb_backend_map = 0x66442200;
+			break;
+		case CHIP_JUNIPER:
+			gb_backend_map = 0x00006420;
+			break;
+		default:
+			gb_backend_map =
+				evergreen_get_tile_pipe_to_backend_map(rdev,
+								       rdev->config.evergreen.max_tile_pipes,
+								       rdev->config.evergreen.max_backends,
+								       ((EVERGREEN_MAX_BACKENDS_MASK <<
+									 rdev->config.evergreen.max_backends) &
+									EVERGREEN_MAX_BACKENDS_MASK));
+		}
+	}
 
 	rdev->config.evergreen.tile_config = gb_addr_config;
 	WREG32(GB_BACKEND_MAP, gb_backend_map);