linux-kernel - Re: [PATCH] Bugfix RTS line config in RS485 mode is overwritten in pl011_set

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Date:   Thu, 13 Jan 2022 11:12:12 +0100 (CET)
From:   Jochen Mades <jochen@...es.net>
To:     Lukas Wunner <lukas@...ner.de>
Cc:     gregkh@...uxfoundation.org, Russell King <linux@...linux.org.uk>,
        Jiri Slaby <jirislaby@...nel.org>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lino Sanfilippo <LinoSanfilippo@....de>,
        Philipp Rosenberger <p.rosenberger@...bus.com>
Subject: Re: [PATCH] Bugfix RTS line config in RS485 mode is overwritten in
 pl011_set_mctrl() function.

Hi Lukas,

> Patch is correct, but commit message could be improved:
> 
> * Subject should be in imperative mood (by convention), it should be
>   prepended by "serial: pl011: " (in line with previous commits touching
>   this driver, use "git log --oneline amba-pl011.c") and the trailing dot
>   is unnecessary, e.g.:
> 
>   "serial: pl011: Fix incorrect rs485 RTS polarity on set_mctrl"
> 
> * Commit message should be wrapped at 72 characters (so that it appears
>   centered when displayed with "git log" on an 80 chars terminal).
>   The reference to "0001-serial-amba-pl011-add-RS485-support.patch"
>   should be replaced with a reference to the offending commit, e.g.:
>
>   "Commit 8d479237727c ("serial: amba-pl011: add RS485 support") sought
>   to keep RTS deasserted on set_mctrl if rs485 is enabled.  However it
>   did so only if deasserted RTS polarity is high.  Fix it in case it's
>   low."
>
>   Feel free to copy this to a v2 of your patch and amend as you see fit.
> 

Find attached the patch with the new subject and corretced commit message.

> * Add tags for the offending commit:
> 
>   Fixes: 8d479237727c ("serial: amba-pl011: add RS485 support")
>   Cc: stable@...r.kernel.org # v5.15+
> 
> * Be sure to cc the author of the offending commit.

Sorry I don't know how to do that correctly. Can you please give support/hints?

 
> Thanks,
> 
> Lukas
> 
> > ---
> >  drivers/tty/serial/amba-pl011.c | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
> > index 537f37ac4..1749c1498 100644
> > --- a/drivers/tty/serial/amba-pl011.c
> > +++ b/drivers/tty/serial/amba-pl011.c
> > @@ -1646,8 +1646,12 @@ static void pl011_set_mctrl(struct uart_port *port, unsigned int mctrl)
> >  	    container_of(port, struct uart_amba_port, port);
> >  	unsigned int cr;
> >  
> > -	if (port->rs485.flags & SER_RS485_ENABLED)
> > -		mctrl &= ~TIOCM_RTS;
> > +	if (port->rs485.flags & SER_RS485_ENABLED) {
> > +		if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
> > +			mctrl &= ~TIOCM_RTS;
> > +		else
> > +			mctrl |= TIOCM_RTS;
> > +	}
> >  
> >  	cr = pl011_read(uap, REG_CR);
Download attachment "0001-serial-pl011-Fix-incorrect-rs485-RTS-polarity-on-set.patch" of type "application/octet-stream" (1210 bytes)