Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> writes:
> Au1x00/RT2800+ doesn't implement the 8250 scratch register (and
> this may be true of other h/w currently supported by the 8250 driver);
> read back the canary value written to the scratch register to enable
> the console h/w restart after resume from system suspend.
>
> Fixes: 4516d50aabedb ("serial: 8250: Use canary to restart console ...")
> Reported-by: Mason <slash.tmp@xxxxxxx>
> Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/tty/serial/8250/8250_core.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
> index 87df908..50c80b1 100644
> --- a/drivers/tty/serial/8250/8250_core.c
> +++ b/drivers/tty/serial/8250/8250_core.c
> @@ -3486,7 +3486,8 @@ void serial8250_suspend_port(int line)
> port->type != PORT_8250) {
> unsigned char canary = 0xa5;
> serial_out(up, UART_SCR, canary);
> - up->canary = canary;
> + if (serial_in(up, UART_SCR) == canary)
> + up->canary = canary;
> }
I think this has the opposite of the intended effect. If there is no
scratch register, up->canary will remain zero, and the reset code in
serial8250_console_write() won't execute even if it is needed.
As it is currently (without this patch), a missing scratch register will
only result in the port possibly being re-initialised unnecessarily,
which should be quite harmless.
--
Måns Rullgård
mans@xxxxxxxxx
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