Hi
On 16:29 Sat 06 Jul , Jisheng Zhang wrote:
> Commit b0b8c84cf58d ("serial: of_serial: Handle auto-flow-control
> property") added support for fifo-size and hw-flow-control properties
> to avoid adding new types to 8250.c for UARTs that are compatible with
> the standard types but that have different size fifo or support 16750
> compatible auto flow control. We avoided many new 8250 port types with
> this nice feature, but there's a problem, if the code detects fifo-size
> or auto-flow-control property, up->capabilities will be set
> accordingly, then serial8250_set_defaults() will ignore the default
> port's capabilities:
>
> |if (!up->capabilities)
> | up->capabilities = uart_config[type].flags;
>
so the previous old logic is trying to override the config of 'type' uart,
while this patch try to extend capabilities with default config of 'type' uart as base
I tend to agree this is right direction (but wasn't 100% sure..)
btw, Jisheng, can you also check serial8250_do_startup()? which has similar logic
> If the port's default capabilities contains other bits such as
> UART_CAP_SLEEP, UART_CAP_EFR and so on, they are lost.
>
> Fixes: b0b8c84cf58d ("serial: of_serial: Handle auto-flow-control property")
I believe the commit just reveal the problem, make it more visible, but not the root cause,
'git blame' lead to b6830f6df8914f ("serial: 8250: Split base port operations from universal driver")
as the original commit introduce this logic which seems exist long time ago..
> Signed-off-by: Jisheng Zhang <jszhang@xxxxxxxxxx>
> ---
> drivers/tty/serial/8250/8250_port.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> index 893bc493f662..e20614241229 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -3245,8 +3245,7 @@ void serial8250_set_defaults(struct uart_8250_port *up)
> up->port.fifosize = uart_config[type].fifo_size;
> if (!up->tx_loadsz)
> up->tx_loadsz = uart_config[type].tx_loadsz;
> - if (!up->capabilities)
> - up->capabilities = uart_config[type].flags;
> + up->capabilities |= uart_config[type].flags;
> }
>
> set_io_from_upio(port);
> --
> 2.43.0
>
--
Yixun Lan (dlan)
Gentoo Linux Developer
GPG Key ID AABEFD55
