Re: [PATCH 1/4] msm_serial: Fix NUL byte output on UARTDM

[David Brown]

On Wed, Jul 24, 2013 at 11:37:28AM -0700, Stephen Boyd wrote:
> UARTDM serial devices require us to wait for the entire TX fifo
> to drain before we can change the contents of the NCF_TX
> register. Furthermore, if we write any characters to the TX fifo
> within the same clock cycle of changing the NCF_TX register the
> NCF_TX register won't latch properly.
>
> To fix these issues we should read back the NCF_TX register to
> delay any TX fifo accesses by a clock cycle and we should wait
> for the TX fifo to drain (instead of just waiting for the fifo to
> be ready to receive more characters). Failure to do so leads to
> random NUL bytes interspersed in the output.
>
> Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
> ---
> drivers/tty/serial/msm_serial.c | 14 +++++++++-----
> drivers/tty/serial/msm_serial.h |  1 +
> 2 files changed, 10 insertions(+), 5 deletions(-)

Acked-by: David Brown <davidb@xxxxxxxxxxxxxx>

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