FW_BLC_SELF_VLV
was_enabled = I915_READ(FW_BLC_SELF_VLV) & FW_CSPWRDWNEN;
I915_WRITE(FW_BLC_SELF_VLV, enable ? FW_CSPWRDWNEN : 0);
POSTING_READ(FW_BLC_SELF_VLV);
wm->cxsr = I915_READ(FW_BLC_SELF_VLV) & FW_CSPWRDWNEN;