diff --git a/drivers/gpu/drm/radeon/r100.c b/drivers/gpu/drm/radeon/r100.c
index 5aa2995..5d14732 100644
--- a/drivers/gpu/drm/radeon/r100.c
+++ b/drivers/gpu/drm/radeon/r100.c
@@ -3809,6 +3809,31 @@
 	rdev->bios = NULL;
 }
 
+/*
+ * Due to how kexec works, it can leave the hw fully initialised when it
+ * boots the new kernel. However doing our init sequence with the CP and
+ * WB stuff setup causes GPU hangs on the RN50 at least. So at startup
+ * do some quick sanity checks and restore sane values to avoid this
+ * problem.
+ */
+void r100_restore_sanity(struct radeon_device *rdev)
+{
+	u32 tmp;
+
+	tmp = RREG32(RADEON_CP_CSQ_CNTL);
+	if (tmp) {
+		WREG32(RADEON_CP_CSQ_CNTL, 0);
+	}
+	tmp = RREG32(RADEON_CP_RB_CNTL);
+	if (tmp) {
+		WREG32(RADEON_CP_RB_CNTL, 0);
+	}
+	tmp = RREG32(RADEON_SCRATCH_UMSK);
+	if (tmp) {
+		WREG32(RADEON_SCRATCH_UMSK, 0);
+	}
+}
+
 int r100_init(struct radeon_device *rdev)
 {
 	int r;
@@ -3821,6 +3846,8 @@
 	radeon_scratch_init(rdev);
 	/* Initialize surface registers */
 	radeon_surface_init(rdev);
+	/* sanity check some register to avoid hangs like after kexec */
+	r100_restore_sanity(rdev);
 	/* TODO: disable VGA need to use VGA request */
 	/* BIOS*/
 	if (!radeon_get_bios(rdev)) {
diff --git a/drivers/gpu/drm/radeon/r300.c b/drivers/gpu/drm/radeon/r300.c
index 7e81db5..3c34da0 100644
--- a/drivers/gpu/drm/radeon/r300.c
+++ b/drivers/gpu/drm/radeon/r300.c
@@ -1377,6 +1377,8 @@
 	/* Initialize surface registers */
 	radeon_surface_init(rdev);
 	/* TODO: disable VGA need to use VGA request */
+	/* restore some register to sane defaults */
+	r100_restore_sanity(rdev);
 	/* BIOS*/
 	if (!radeon_get_bios(rdev)) {
 		if (ASIC_IS_AVIVO(rdev))
diff --git a/drivers/gpu/drm/radeon/r420.c b/drivers/gpu/drm/radeon/r420.c
index e6c8914..59f7bcc 100644
--- a/drivers/gpu/drm/radeon/r420.c
+++ b/drivers/gpu/drm/radeon/r420.c
@@ -343,6 +343,8 @@
 	/* Initialize surface registers */
 	radeon_surface_init(rdev);
 	/* TODO: disable VGA need to use VGA request */
+	/* restore some register to sane defaults */
+	r100_restore_sanity(rdev);
 	/* BIOS*/
 	if (!radeon_get_bios(rdev)) {
 		if (ASIC_IS_AVIVO(rdev))
diff --git a/drivers/gpu/drm/radeon/r520.c b/drivers/gpu/drm/radeon/r520.c
index 34330df..213e2e0 100644
--- a/drivers/gpu/drm/radeon/r520.c
+++ b/drivers/gpu/drm/radeon/r520.c
@@ -230,6 +230,8 @@
 	radeon_scratch_init(rdev);
 	/* Initialize surface registers */
 	radeon_surface_init(rdev);
+	/* restore some register to sane defaults */
+	r100_restore_sanity(rdev);
 	/* TODO: disable VGA need to use VGA request */
 	/* BIOS*/
 	if (!radeon_get_bios(rdev)) {
diff --git a/drivers/gpu/drm/radeon/radeon_asic.h b/drivers/gpu/drm/radeon/radeon_asic.h
index c0bbaa6..a5aff75 100644
--- a/drivers/gpu/drm/radeon/radeon_asic.h
+++ b/drivers/gpu/drm/radeon/radeon_asic.h
@@ -113,6 +113,7 @@
 int r100_wb_init(struct radeon_device *rdev);
 int r100_cp_reset(struct radeon_device *rdev);
 void r100_vga_render_disable(struct radeon_device *rdev);
+void r100_restore_sanity(struct radeon_device *rdev);
 int r100_cs_track_check_pkt3_indx_buffer(struct radeon_cs_parser *p,
 					 struct radeon_cs_packet *pkt,
 					 struct radeon_bo *robj);
diff --git a/drivers/gpu/drm/radeon/rs400.c b/drivers/gpu/drm/radeon/rs400.c
index 9e4240b..c178481 100644
--- a/drivers/gpu/drm/radeon/rs400.c
+++ b/drivers/gpu/drm/radeon/rs400.c
@@ -480,6 +480,8 @@
 	/* Initialize surface registers */
 	radeon_surface_init(rdev);
 	/* TODO: disable VGA need to use VGA request */
+	/* restore some register to sane defaults */
+	r100_restore_sanity(rdev);
 	/* BIOS*/
 	if (!radeon_get_bios(rdev)) {
 		if (ASIC_IS_AVIVO(rdev))
diff --git a/drivers/gpu/drm/radeon/rs600.c b/drivers/gpu/drm/radeon/rs600.c
index 27d2e70..c576092 100644
--- a/drivers/gpu/drm/radeon/rs600.c
+++ b/drivers/gpu/drm/radeon/rs600.c
@@ -879,6 +879,8 @@
 	radeon_scratch_init(rdev);
 	/* Initialize surface registers */
 	radeon_surface_init(rdev);
+	/* restore some register to sane defaults */
+	r100_restore_sanity(rdev);
 	/* BIOS */
 	if (!radeon_get_bios(rdev)) {
 		if (ASIC_IS_AVIVO(rdev))
diff --git a/drivers/gpu/drm/radeon/rs690.c b/drivers/gpu/drm/radeon/rs690.c
index 23676b6..3dde54d 100644
--- a/drivers/gpu/drm/radeon/rs690.c
+++ b/drivers/gpu/drm/radeon/rs690.c
@@ -707,6 +707,8 @@
 	radeon_scratch_init(rdev);
 	/* Initialize surface registers */
 	radeon_surface_init(rdev);
+	/* restore some register to sane defaults */
+	r100_restore_sanity(rdev);
 	/* TODO: disable VGA need to use VGA request */
 	/* BIOS*/
 	if (!radeon_get_bios(rdev)) {
diff --git a/drivers/gpu/drm/radeon/rv515.c b/drivers/gpu/drm/radeon/rv515.c
index 7d9a7b0..3f04f73 100644
--- a/drivers/gpu/drm/radeon/rv515.c
+++ b/drivers/gpu/drm/radeon/rv515.c
@@ -468,6 +468,8 @@
 	/* Initialize surface registers */
 	radeon_surface_init(rdev);
 	/* TODO: disable VGA need to use VGA request */
+	/* restore some register to sane defaults */
+	r100_restore_sanity(rdev);
 	/* BIOS*/
 	if (!radeon_get_bios(rdev)) {
 		if (ASIC_IS_AVIVO(rdev))