CTRL_DL
if (read_iir & CTRL_DL) {
writew(CTRL_DL, dc->reg_fcr);
dc->last_ier = dc->last_ier | CTRL_DL;
static const u16 mask[] = {MDM_DL, DIAG_DL, APP1_DL, APP2_DL, CTRL_DL};
{~MDM_DL, ~DIAG_DL, ~APP1_DL, ~APP2_DL, ~CTRL_DL};
if (interrupt & CTRL_DL)