linux-kernel - Re: [PATCH] serial: mvebu: Apply old baudrate to termios

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Message-ID: <20220628095942.rbpl2iocxoqtzxiy@pali>
Date:   Tue, 28 Jun 2022 11:59:42 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Allen Yan <yanwei@...vell.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Gregory CLEMENT <gregory.clement@...tlin.com>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] serial: mvebu: Apply old baudrate to termios

On Tuesday 28 June 2022 11:51:36 Pali Rohár wrote:
> On Tuesday 28 June 2022 12:41:55 Ilpo Järvinen wrote:
> > A fallback baud rate was derived from old termios but got never applied
> > to (new/current) termios. Old termios is dropped once ->set_termios()
> > call chain completes, only termios persists the values. Encode also the
> > old baud rate into termios.
> > 
> > Fixes: 68a0db1d7da2 ("serial: mvebu-uart: add function to change baudrate")
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> 
> Hello! Could you explain a bit more what is this patch fixing? I have
> not caught it yet. Do you have a test scenario which can demonstrate
> this issue? Because I have tested this driver more deeply (on Mox
> and Espressobin) and I have not seen any remaining issue with reporting
> incorrect baudrate.

Ou, now I see where is the issue. Patch which I tested and which fixes
reporting baudrate is not in kernel tree yet and it looks like I totally
forgot to sent it to ML. I will send it. Sorry for confusion.

> > ---
> >  drivers/tty/serial/mvebu-uart.c | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/tty/serial/mvebu-uart.c b/drivers/tty/serial/mvebu-uart.c
> > index 0429c2a54290..12a79018697f 100644
> > --- a/drivers/tty/serial/mvebu-uart.c
> > +++ b/drivers/tty/serial/mvebu-uart.c
> > @@ -592,10 +592,9 @@ static void mvebu_uart_set_termios(struct uart_port *port,
> >  		if (old)
> >  			baud = uart_get_baud_rate(port, old, NULL,
> >  						  min_baud, max_baud);
> > -	} else {
> > -		tty_termios_encode_baud_rate(termios, baud, baud);
> > -		uart_update_timeout(port, termios->c_cflag, baud);
> >  	}
> > +	tty_termios_encode_baud_rate(termios, baud, baud);
> > +	uart_update_timeout(port, termios->c_cflag, baud);
> >  
> >  	/* Only the following flag changes are supported */
> >  	if (old) {
> > 
> > -- 
> > tg: (f287f971e256..) fix/mvebu-apply-old-baud (depends on: tty-next)