RE: [PATCH v2 1/2] serial: sh-sci: Avoid divide-by-zero fault

[Biju Das]

Hi Hugo,

Thanks for the feedback.

> -----Original Message-----
> From: Hugo Villeneuve <hugo@xxxxxxxxxxx>
> Sent: 08 April 2026 17:31
> Subject: Re: [PATCH v2 1/2] serial: sh-sci: Avoid divide-by-zero fault
> 
> Hi Biju,
> 
> On Wed,  8 Apr 2026 15:20:58 +0100
> Biju <biju.das.au@xxxxxxxxx> wrote:
> 
> > From: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> >
> > uart_update_timeout() computes a timeout value by dividing by the baud
> > rate. If baud is zero — which can occur when the hardware returns an
> > unsupported or invalid rate — this results in a divide-by-zero fault.
> 
> baud is returned by uart_get_baud_rate(), so this is not returned by the hardware?

You are tight, Will update commit description.
> 
> 
> >
> > Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> 
> Missing Fixes tag?

I will split patch into 2 adding Fixes tag.

> 
> 
> > ---
> > v2:
> >  * New patch
> > ---
> >  drivers/tty/serial/rsci.c   | 3 ++-
> >  drivers/tty/serial/sh-sci.c | 3 ++-
> >  2 files changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/tty/serial/rsci.c b/drivers/tty/serial/rsci.c
> > index b00c9e385169..a0858bab0822 100644
> > --- a/drivers/tty/serial/rsci.c
> > +++ b/drivers/tty/serial/rsci.c
> > @@ -286,7 +286,8 @@ static void rsci_set_termios(struct uart_port *port, struct ktermios *termios,
> >  	sci_port_enable(s);
> >  	uart_port_lock_irqsave(port, &flags);
> >
> > -	uart_update_timeout(port, termios->c_cflag, baud);
> > +	if (baud)
> > +		uart_update_timeout(port, termios->c_cflag, baud);
> >
> >  	rsci_serial_out(port, CCR0, ccr0_val);
> >
> > diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
> > index 6c819b6b2425..429e89106ee3 100644
> > --- a/drivers/tty/serial/sh-sci.c
> > +++ b/drivers/tty/serial/sh-sci.c
> > @@ -2805,7 +2805,8 @@ static void sci_set_termios(struct uart_port
> > *port, struct ktermios *termios,
> >
> >  	sci_reset(port);
> >
> > -	uart_update_timeout(port, termios->c_cflag, baud);
> > +	if (baud)
> > +		uart_update_timeout(port, termios->c_cflag, baud);
> 
> After this patch, have you re-tested if having baud = 0 produces any other errors? A litle bit later in
> the same function, there is this
> code:

+	/* Avoid divide-by-zero fault in divider operations */
+	if (!baud)
+		baud = 100;
+

Plan is to update the code with the above change, that will cover
All divide-by-zero case in this function.

Cheers,
Biju