FW_CSPWRDWNEN
was_enabled = intel_de_read(display, FW_BLC_SELF_VLV) & FW_CSPWRDWNEN;
intel_de_write(display, FW_BLC_SELF_VLV, enable ? FW_CSPWRDWNEN : 0);
wm->cxsr = intel_de_read(display, FW_BLC_SELF_VLV) & FW_CSPWRDWNEN;
sr_enabled = intel_de_read(display, FW_BLC_SELF_VLV) & FW_CSPWRDWNEN;