+
+}
+
+static void radeon_test_writeback(drm_radeon_private_t * dev_priv)
+{
+ u32 tmp;
+
+ /* Writeback doesn't seem to work everywhere, test it here and possibly
+ * enable it if it appears to work
+ */
+ DRM_WRITE32(dev_priv->ring_rptr, RADEON_SCRATCHOFF(1), 0);
+ RADEON_WRITE(RADEON_SCRATCH_REG1, 0xdeadbeef);
+
+ for (tmp = 0; tmp < dev_priv->usec_timeout; tmp++) {
+ if (DRM_READ32(dev_priv->ring_rptr, RADEON_SCRATCHOFF(1)) ==
+ 0xdeadbeef)
+ break;
+ DRM_UDELAY(1);
+ }
+
+ if (tmp < dev_priv->usec_timeout) {
+ dev_priv->writeback_works = 1;
+ DRM_INFO("writeback test succeeded in %d usecs\n", tmp);
+ } else {
+ dev_priv->writeback_works = 0;
+ DRM_INFO("writeback test failed\n");
+ }
+ if (radeon_no_wb == 1) {
+ dev_priv->writeback_works = 0;
+ DRM_INFO("writeback forced off\n");
+ }
+
+ if (!dev_priv->writeback_works) {
+ /* Disable writeback to avoid unnecessary bus master transfer */
+ RADEON_WRITE(RADEON_CP_RB_CNTL, RADEON_READ(RADEON_CP_RB_CNTL) |
+ RADEON_RB_NO_UPDATE);
+ RADEON_WRITE(RADEON_SCRATCH_UMSK, 0);
+ }