mmPRESCALE_GRPH_CONTROL
tmp = RREG32(mmPRESCALE_GRPH_CONTROL + amdgpu_crtc->crtc_offset);
WREG32(mmPRESCALE_GRPH_CONTROL + amdgpu_crtc->crtc_offset, tmp);
WREG32(mmPRESCALE_GRPH_CONTROL + amdgpu_crtc->crtc_offset,
WREG32(mmPRESCALE_GRPH_CONTROL + amdgpu_crtc->crtc_offset,