Re: [PATCH v7 1/3] serial: sc16is7xx: announce support of SER_RS485_RTS_ON_SEND

Hugo Villeneuve
2024-04-23T18:59:36Z

On Mon, 22 Apr 2024 16:32:13 +0300
Konstantin Pugin <ria.freelander@gmail.com> wrote:

Hi Konstantin,

> The hardware supports both RTS_ON_SEND and RTS_AFTER_SEND modes, but
> after the commit 4afeced55baa ("serial: core: fix sanitizing check for
> RTS settings") we always end up with SER_RS485_RTS_AFTER_SEND set and
> always write to the register field SC16IS7XX_EFCR_RTS_INVERT_BIT, which
> breaks some hardware using these chips.

it took me a long time to properly understand what you meant in your
commit message. In my setup, I have the property rs485-rts-active-low
defined, and couldn't reproduce the problem. It is only after I
commented this property that I got a warning about the "invalid RTS
setting"... I also got it by defining rs485-rts-active-high.

I suggest the following changes to the commit message:

----
When specifying flag SER_RS485_RTS_ON_SEND in RS485 configuration,
we get the following warning after commit 4afeced55baa ("serial: core:
fix sanitizing check for RTS settings"):

invalid RTS setting, using RTS_AFTER_SEND instead

This results in SER_RS485_RTS_AFTER_SEND being set and the
driver always write to the register field SC16IS7XX_EFCR_RTS_INVERT_BIT,
which breaks some hardware using these chips.

The hardware supports both RTS_ON_SEND and RTS_AFTER_SEND modes, so fix
this by announcing support for RTS_ON_SEND.
---

If you agree to these changes, feel free to add:

Tested-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>

Hugo.

>
> Fixes: 267913ecf737 ("serial: sc16is7xx: Fill in rs485_supported")
> Signed-off-by: Konstantin Pugin <ria.freelander@gmail.com>
> ---
> drivers/tty/serial/sc16is7xx.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
> index 03cf30e20b75..dfcc804f558f 100644
> --- a/drivers/tty/serial/sc16is7xx.c
> +++ b/drivers/tty/serial/sc16is7xx.c
> @@ -1449,7 +1449,7 @@ static int sc16is7xx_setup_mctrl_ports(struct sc16is7xx_port *s,
> }
>
> static const struct serial_rs485 sc16is7xx_rs485_supported = {
> - .flags = SER_RS485_ENABLED | SER_RS485_RTS_AFTER_SEND,
> + .flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND | SER_RS485_RTS_AFTER_SEND,
> .delay_rts_before_send = 1,
> .delay_rts_after_send = 1, /* Not supported but keep returning -EINVAL */
> };
> --
> 2.34.1
>
>
>

--
Hugo Villeneuve