Re: [PATCH v3 2/3] serial: sb1250-duart: Fix bootconsole handover lockup

On 6/8/26 12:54, Maciej W. Rozycki wrote:
> Calling sbd_init_port() in the course of setting up the serial device
> causes line parameters to be messed up and the transmitter disabled.
> We've been lucky in that no message is usually produced to the kernel
> log between this call and the later call to uart_set_options() in the
> course of console setup done by sbd_serial_console_init(), or the system
> would hang as the console output handler in CFE tried to access a port
> whose transmitter has been disabled and line parameters messed up.
> 
> It'll change with the next change to the driver, so fix sbd_init_port()
> such that line parameters are set for 115200n8 console operation as with
> the CFE firmware and the transmitter re-enabled after reset.
> 
> Fixes: 84a9582fd203 ("serial: core: Start managing serial controllers to enable runtime PM")
> Signed-off-by: Maciej W. Rozycki <[email protected]>
> Cc: [email protected] # v6.5+
> ---
> No change from v2 (2/3),
> <https://lore.kernel.org/r/[email protected]/>.
> 
> Changes from v1 (2/4),
> <https://lore.kernel.org/r/[email protected]/>:
> 
> - Sanitise the change heading.
> ---
>   drivers/tty/serial/sb1250-duart.c |    7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> linux-serial-sb1250-duart-prom-console.diff
> Index: linux-macro/drivers/tty/serial/sb1250-duart.c
> ===================================================================
> --- linux-macro.orig/drivers/tty/serial/sb1250-duart.c
> +++ linux-macro/drivers/tty/serial/sb1250-duart.c
> @@ -542,14 +542,19 @@ static void sbd_init_port(struct sbd_por
>   	/* There is no DUART reset feature, so just set some sane defaults.  */
>   	write_sbdchn(sport, R_DUART_CMD, V_DUART_MISC_CMD_RESET_TX);
>   	write_sbdchn(sport, R_DUART_CMD, V_DUART_MISC_CMD_RESET_RX);
> -	write_sbdchn(sport, R_DUART_MODE_REG_1, V_DUART_BITS_PER_CHAR_8);
> +	write_sbdchn(sport, R_DUART_MODE_REG_1,
> +		     V_DUART_PARITY_MODE_NONE | V_DUART_BITS_PER_CHAR_8);
>   	write_sbdchn(sport, R_DUART_MODE_REG_2, 0);
> +	write_sbdchn(sport, R_DUART_CLK_SEL, V_DUART_BAUD_RATE(115200));
>   	write_sbdchn(sport, R_DUART_FULL_CTL,
>   		     V_DUART_INT_TIME(0) | V_DUART_SIG_FULL(15));
>   	write_sbdchn(sport, R_DUART_OPCR_X, 0);
>   	write_sbdchn(sport, R_DUART_AUXCTL_X, 0);
>   	write_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2), 0);
>   
> +	/* Re-enable transmission for the initial PROM-based console.  */
> +	write_sbdchn(sport, R_DUART_CMD, M_DUART_TX_EN);
> +
>   	sport->initialised = 1;
>   }
>   
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>