IG4_REG_TX_TL
reg_write(sc, IG4_REG_TX_TL, 0);
v = reg_read(sc, IG4_REG_TX_TL);
reg_write(sc, IG4_REG_TX_TL, v | IG4_FIFO_MASK);
(reg_read(sc, IG4_REG_TX_TL) & IG4_FIFO_MASK) + 1;
reg_write(sc, IG4_REG_TX_TL, v);
REGDUMP(sc, IG4_REG_TX_TL);
reg_write(sc, IG4_REG_TX_TL, 0);
reg_write(sc, IG4_REG_TX_TL, IG4_FIFO_LOWAT);
reg_write(sc, IG4_REG_TX_TL, lowat);