From: "Maciej W. Rozycki" This is an update to the zs.c driver to make it wait for the transmission line to become idle before disabling the transmitter or resetting the chip. This way the character that is on the way at the time one of these actions is about to be performed does not get corrupted. Plus a change to reset the index/data pointer first before issuing a chip reset just in case the state is wrong when control of the chip is taken the first time. Signed-off-by: Maciej W. Rozycki Cc: Ralf Baechle Signed-off-by: Andrew Morton --- drivers/serial/zs.c | 20 +++++++++++++++++++- 1 files changed, 19 insertions(+), 1 deletion(-) diff -puN drivers/serial/zs.c~zsc-drain-the-transmission-line drivers/serial/zs.c --- a/drivers/serial/zs.c~zsc-drain-the-transmission-line +++ a/drivers/serial/zs.c @@ -240,10 +240,24 @@ static int zs_transmit_drain(struct zs_p return loops; } +static int zs_line_drain(struct zs_port *zport, int irq) +{ + struct zs_scc *scc = zport->scc; + int loops = 10000; + + while (!(read_zsreg(zport, R1) & ALL_SNT) && loops--) { + zs_spin_unlock_cond_irq(&scc->zlock, irq); + udelay(2); + zs_spin_lock_cond_irq(&scc->zlock, irq); + } + return loops; +} + static void load_zsregs(struct zs_port *zport, u8 *regs, int irq) { - zs_transmit_drain(zport, irq); + /* Let the current transmission finish. */ + zs_line_drain(zport, irq); /* Load 'em up. */ write_zsreg(zport, R3, regs[3] & ~RxENABLE); write_zsreg(zport, R5, regs[5] & ~TxENAB); @@ -814,6 +828,10 @@ static void zs_reset(struct zs_port *zpo spin_lock_irqsave(&scc->zlock, flags); irq = !irqs_disabled_flags(flags); if (!scc->initialised) { + /* Reset the pointer first, just in case... */ + read_zsreg(zport, R0); + /* And let the current transmission finish. */ + zs_line_drain(zport, irq); write_zsreg(zport, R9, FHWRES); udelay(10); write_zsreg(zport, R9, 0); _