CCK_DISPLAY_CLOCK_CONTROL
CCK_DISPLAY_CLOCK_CONTROL,
val = vlv_cck_read(display->drm, CCK_DISPLAY_CLOCK_CONTROL);
vlv_cck_write(display->drm, CCK_DISPLAY_CLOCK_CONTROL, val);
ret = poll_timeout_us(val = vlv_cck_read(display->drm, CCK_DISPLAY_CLOCK_CONTROL),