mmMAILBOX_MSGBUF_TRN_DW0
WREG32_NO_KIQ(mmMAILBOX_MSGBUF_TRN_DW0, req);
reg = RREG32_NO_KIQ(mmMAILBOX_MSGBUF_TRN_DW0);
WREG32_NO_KIQ(mmMAILBOX_MSGBUF_TRN_DW0, reg);