Hi Dave,

On Thu, May 21, 2015 at 04:37:49PM +0100, Dave Martin wrote:

Commit 734745caeb9f155ab58918834a8c70e83fa6afd3 serial/amba-pl011:
(Activate TX IRQ passively) introduces a race which causes the driver
sometimes to attempt to write a character to the TX FIFO when the FIFO
is already full.

The PL011 does not guarantee its behaviour when the FIFO is overfilled.
In practice, this can cause duplicate and/or dropped characters to be
output on the wire.  The problem is common enough to be readily
observable on the ARM Juno platform when the PL011 UART is used as
the console and DMA is not in use.

This patch fixes this problem by always polling for space before each
character is written to the FIFO.

This will be amended to a less brute-force approach in a later commit,
but this patch should help ensure correct behaviour for now.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
---

Do you know if this patch has been applied anywhere? Without it, poor
old systemd has an identity crisis when run under 4.1-rc4, alternating
between Scottish:

  [  OK  ] Stopped Regularr background proogram processing daemon.

and Old English:

  [  OK  ] Started Tell Pllymouth To Writee Out Runtime Data.
  Starting Copy rules geneerated while thee root was ro...

Will