drm: add option to force writeback off.

In order to get some better debugging from people about certain hangs/crashes
we need to be able to turn AGP writeback off permanently...

Signed-off-by: Dave Airlie <airlied@linux.ie>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/char/drm/radeon_drv.c b/drivers/char/drm/radeon_drv.c
index 6c1766120c10..7074d01ed1dd 100644
--- a/drivers/char/drm/radeon_drv.c
+++ b/drivers/char/drm/radeon_drv.c
@@ -37,6 +37,11 @@
 
 #include "drm_pciids.h"
 
+int radeon_no_wb;
+
+MODULE_PARM_DESC(no_wb, "Disable AGP writeback for scratch registers\n");
+module_param_named(no_wb, radeon_no_wb, int, 0444);
+
 static int postinit(struct drm_device *dev, unsigned long flags)
 {
         DRM_INFO("Initialized %s %d.%d.%d %s on minor %d: %s\n",