linux-kernel - Re: [PATCH 4.19 177/639] rtc: ds1307: rx8130: Fix alarm handling

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Date:   Sun, 26 Jan 2020 22:28:23 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Pavel Machek <pavel@...x.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 177/639] rtc: ds1307: rx8130: Fix alarm handling

On Sat, Jan 25, 2020 at 02:30:36PM +0100, Pavel Machek wrote:
> Hi!
> 
> > When the EXTENSION.WADA bit is set, register 0x19 contains a bitmap of
> > week days, not a day of month. As Linux only handles a single alarm
> > without repetition using day of month is more flexible, so clear this
> > bit. (Otherwise a value depending on time.tm_wday would have to be
> > written to register 0x19.)
> 
> So the comment explains why WADA bit needs to be clear.
> 
> > @@ -749,8 +749,8 @@ static int rx8130_set_alarm(struct device *dev, struct rtc_wkalrm *t)
> >  	if (ret < 0)
> >  		return ret;
> >  
> > -	ctl[0] &= ~RX8130_REG_EXTENSION_WADA;
> > +	ctl[0] &= RX8130_REG_EXTENSION_WADA;
> 
> But then code is changed to preserve WADA bit while it was clearing it
> before.

This looks broken indeed. The new code clears all flags but WADA. Will
take a look tomorrow.
 
Best regards
Uwe



-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |