Re: [PATCH v2] serial: 8250_bcm7271: Save/restore RTS in suspend/resume

[Florian Fainelli]

On 7/3/2022 11:40 PM, Jiri Slaby wrote:
> On 29. 06. 22, 18:02, Florian Fainelli wrote:
> > From: Doug Berger <opendmb@xxxxxxxxx>
> >
> > Commit 9cabe26e65a8 ("serial: 8250_bcm7271: UART errors after resuming
> > from S2") prevented an early enabling of RTS during resume, but it did
> > not actively restore the RTS state after resume.
> >
> > Fixes: 9cabe26e65a8 ("serial: 8250_bcm7271: UART errors after resuming 
> > from S2")
> > Signed-off-by: Doug Berger <opendmb@xxxxxxxxx>
> > Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
> > ---
> >   drivers/tty/serial/8250/8250_bcm7271.c | 24 ++++++++++++++++++------
> >   1 file changed, 18 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/tty/serial/8250/8250_bcm7271.c 
> > b/drivers/tty/serial/8250/8250_bcm7271.c
> > index 9b878d023dac..b9cea38c8aff 100644
> > --- a/drivers/tty/serial/8250/8250_bcm7271.c
> > +++ b/drivers/tty/serial/8250/8250_bcm7271.c
> ...
> > @@ -1180,7 +1184,15 @@ static int __maybe_unused 
> > brcmuart_resume(struct device *dev)
> >           start_rx_dma(serial8250_get_port(priv->line));
> >       }
> >       serial8250_resume_port(priv->line);
> > -    port->mctrl = priv->saved_mctrl;
> > +
> > +    if (priv->saved_mctrl & TIOCM_RTS) {
> > +        /* Restore RTS */
> > +        spin_lock_irqsave(&port->lock, flags);
> > +        port->mctrl |= TIOCM_RTS;
> > +        spin_unlock_irqrestore(&port->lock, flags);
> > +        port->ops->set_mctrl(port, port->mctrl);
>
> Calling ->set_mctrl w/o port->lock doesn't look really safe.

Good point, I will check with Doug whether this was intentional and if 
so, why, and if not why should we move it up under the spinlock.

Thanks!
--
Florian