Le 09/01/2023 à 08:29, Tobias Schramm a écrit :
> Commit ba47f97a18f2 ("serial: core: remove baud_rates when serial console
> setup") changed uart_set_options to select the correct baudrate
> configuration based on the absolute error between requested baudrate and
> available standard baudrate settings.
> Prior to that commit the baudrate was selected based on which predefined
> standard baudrate did not exceed the requested baudrate.
> This change of selection logic was never reflected in the atmel serial
> driver. Thus the comment left in the atmel serial driver is no longer
> accurate.
> Additionally the manual rounding up described in that comment and applied
> via (quot - 1) requests an incorrect baudrate. Since uart_set_options uses
> tty_termios_encode_baud_rate to determine the appropriate baudrate flags
> this can cause baudrate selection to fail entirely because
> tty_termios_encode_baud_rate will only select a baudrate if relative error
> between requested and selected baudrate does not exceed +/-2%.
> Fix that by requesting actual, exact baudrate used by the serial.
>
> Fixes: ba47f97a18f2 ("serial: core: remove baud_rates when serial console setup")
> Signed-off-by: Tobias Schramm <t.schramm@xxxxxxxxxxx>
Acked-by: Richard Genoud <richard.genoud@xxxxxxxxx>
Tested-on sam9g35
> ---
> drivers/tty/serial/atmel_serial.c | 8 +-------
> 1 file changed, 1 insertion(+), 7 deletions(-)
>
> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> index f1c06e12efa0..9cd7479b03c0 100644
> --- a/drivers/tty/serial/atmel_serial.c
> +++ b/drivers/tty/serial/atmel_serial.c
> @@ -2657,13 +2657,7 @@ static void __init atmel_console_get_options(struct uart_port *port, int *baud,
> else if (mr == ATMEL_US_PAR_ODD)
> *parity = 'o';
>
> - /*
> - * The serial core only rounds down when matching this to a
> - * supported baud rate. Make sure we don't end up slightly
> - * lower than one of those, as it would make us fall through
> - * to a much lower baud rate than we really want.
> - */
> - *baud = port->uartclk / (16 * (quot - 1));
> + *baud = port->uartclk / (16 * quot);
> }
>
> static int __init atmel_console_setup(struct console *co, char *options)
Thanks !
Regards,
Richard
