linux-kernel - RE: rtc: pcf85363/pcf85263: fix error that failed to run hwclock -w

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Date:   Thu, 15 Aug 2019 04:14:51 +0000
From:   Biwen Li <biwen.li@....com>
To:     Leo Li <leoyang.li@....com>,
        "a.zummo@...ertech.it" <a.zummo@...ertech.it>,
        "alexandre.belloni@...tlin.com" <alexandre.belloni@...tlin.com>
CC:     "linux-rtc@...r.kernel.org" <linux-rtc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: rtc: pcf85363/pcf85263: fix error that failed to run hwclock -w

> > Subject: rtc: pcf85363/pcf85263: fix error that failed to run hwclock
> > -w
> >
> > Issue:
> >     # hwclock -w
> >     hwclock: RTC_SET_TIME: Invalid argument
> >
> > The patch fixes error when run command hwclock -w with rtc
> > pcf85363/pcf85263
> 
> Can you explain a little bit more in the commit message on how the changes fix
> the above issue?   It is not that clear just from the code.
1. Relative patch: https://lkml.org/lkml/2019/4/3/55 , this patch will always
check for unwritable registers, it will compare reg with max_register in regmap_writeable.

2. In drivers/rtc/rtc-pcf85363.c, CTRL_STOP_EN is 0x2e, but DT_100THS is 0, max_regiter is 0x2f,
then reg will be equal to 0x30, '0x30 < 0x2f' is false,so regmap_writeable will return false.

> 
> >
> > Signed-off-by: Biwen Li <biwen.li@....com>
> > ---
> >  drivers/rtc/rtc-pcf85363.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/rtc/rtc-pcf85363.c b/drivers/rtc/rtc-pcf85363.c
> > index a075e77617dc..3450d615974d 100644
> > --- a/drivers/rtc/rtc-pcf85363.c
> > +++ b/drivers/rtc/rtc-pcf85363.c
> > @@ -166,7 +166,12 @@ static int pcf85363_rtc_set_time(struct device
> > *dev, struct rtc_time *tm)
> >  	buf[DT_YEARS] = bin2bcd(tm->tm_year % 100);
> >
> >  	ret = regmap_bulk_write(pcf85363->regmap, CTRL_STOP_EN,
> > -				tmp, sizeof(tmp));
> > +				tmp, 2);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = regmap_bulk_write(pcf85363->regmap, DT_100THS,
> > +				buf, sizeof(tmp) - 2);
> >  	if (ret)
> >  		return ret;
> >
> > --
> > 2.17.1