drm/radeon/rv740: fix backend setup

This patch fixes occlusion queries and rendering errors
on rv740 boards. Hardcoding the backend map is not an optimal
solution, but a better fix is being worked on.
Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/r600_cp.c

@@ -1439,6 +1439,9 @@ static void r700_gfx_init(struct drm_device *dev,
 
 	gb_tiling_config |= R600_BANK_SWAPS(1);
 
+	if ((dev_priv->flags & RADEON_FAMILY_MASK) == CHIP_RV740)
+		backend_map = 0x28;
+	else
 		backend_map = r700_get_tile_pipe_to_backend_map(dev_priv->r600_max_tile_pipes,
 								dev_priv->r600_max_backends,
 								(0xff << dev_priv->r600_max_backends) & 0xff);

drivers/gpu/drm/radeon/rv770.c

@@ -556,6 +556,9 @@ static void rv770_gpu_init(struct radeon_device *rdev)
 
 	gb_tiling_config |= BANK_SWAPS(1);
 
+	if (rdev->family == CHIP_RV740)
+		backend_map = 0x28;
+	else
 		backend_map = r700_get_tile_pipe_to_backend_map(rdev->config.rv770.max_tile_pipes,
 								rdev->config.rv770.max_backends,
 								(0xff << rdev->config.rv770.max_backends) & 0xff);