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Date: Thu, 01 Feb 2024 15:49:06 +0000
To: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
From: Emil Kronborg <emil.kronborg@protonmail.com>
Cc: gregkh@linuxfoundation.org, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] serial: mxs-auart: fix tx
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On Thu, Feb 01, 2024 at 11:55 +0100, Jiri Slaby (SUSE) wrote:
> Emil reports:
>   After updating Linux on an i.MX28 board, serial communication over
>   AUART broke. When I TX from the board and measure on the TX pin, it
>   seems like the HW fifo is not emptied before the transmission is
>   stopped.
>=20
> MXS performs weird things with stop_tx(). The driver makes it
> conditional on uart_tx_stopped().
>=20
> So the driver needs special handling. Pass the brand new UART_TX_NOSTOP
> to uart_port_tx_flags() and handle the stop on its own.
>=20
> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
> Reported-by: Emil Kronborg <emil.kronborg@protonmail.com>
> Fixes: 2d141e683e9a ("tty: serial: use uart_port_tx() helper")
> Closes: https://lore.kernel.org/all/miwgbnvy3hjpnricubg76ytpn7xoceehwahup=
y25bubbduu23s@om2lptpa26xw/
> ---
>  drivers/tty/serial/mxs-auart.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>=20
> diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auar=
t.c
> index 3ec725555bcc..4749331fe618 100644
> --- a/drivers/tty/serial/mxs-auart.c
> +++ b/drivers/tty/serial/mxs-auart.c
> @@ -605,13 +605,16 @@ static void mxs_auart_tx_chars(struct mxs_auart_por=
t *s)
>  =09=09return;
>  =09}
>=20
> -=09pending =3D uart_port_tx(&s->port, ch,
> +=09pending =3D uart_port_tx_flags(&s->port, ch, UART_TX_NOSTOP,
>  =09=09!(mxs_read(s, REG_STAT) & AUART_STAT_TXFF),
>  =09=09mxs_write(ch, s, REG_DATA));
>  =09if (pending)
>  =09=09mxs_set(AUART_INTR_TXIEN, s, REG_INTR);
>  =09else
>  =09=09mxs_clr(AUART_INTR_TXIEN, s, REG_INTR);
> +
> +=09if (uart_tx_stopped(&s->port))
> +               mxs_auart_stop_tx(&s->port);
>  }
>=20
>  static void mxs_auart_rx_char(struct mxs_auart_port *s)
> --
> 2.43.0
>=20

Tested on i.MX28.

Tested-by: Emil Kronborg <emil.kronborg@protonmail.com>

--=20
Emil Kronborg