drm/radeon/kms: r420 idle after programming GA_ENHANCE

https://bugs.freedesktop.org/show_bug.cgi?id=24041

The idle allows rs690 to startup properly.
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/r420.c

@@ -64,6 +64,11 @@ void r420_pipes_init(struct radeon_device *rdev)
 
 	/* GA_ENHANCE workaround TCL deadlock issue */
 	WREG32(0x4274, (1 << 0) | (1 << 1) | (1 << 2) | (1 << 3));
+	/* add idle wait as per freedesktop.org bug 24041 */
+	if (r100_gui_wait_for_idle(rdev)) {
+		printk(KERN_WARNING "Failed to wait GUI idle while "
+		       "programming pipes. Bad things might happen.\n");
+	}
 	/* get max number of pipes */
 	gb_pipe_select = RREG32(0x402C);
 	num_pipes = ((gb_pipe_select >> 12) & 3) + 1;