linux-kernel - Re: [v2] rtc: pcf85363/pcf85263: fix error that failed to run hwclock -w

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Message-ID: <20190821114722.GF5128@sirena.co.uk>
Date:   Wed, 21 Aug 2019 12:47:22 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Li Yang <leoyang.li@....com>, nandor.han@...sala.com,
        Biwen Li <biwen.li@....com>, a.zummo@...ertech.it,
        linux-rtc@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>
Subject: Re: [v2] rtc: pcf85363/pcf85263: fix error that failed to run
 hwclock -w

On Wed, Aug 21, 2019 at 01:38:56PM +0200, Alexandre Belloni wrote:
> On 21/08/2019 12:30:29+0100, Mark Brown wrote:

> > What's the mechanism here?  It's a very strange thing to require.

> The clock control is on the first register, then you have sec, min,
> hour, day, mon, year.

> To be able to set the clock accurately, you need to first disable the
> clock, then set the time and date and finally reenable the clock in the
> first register. This should be done in a single i2c write.

Ugh, right.  And of course it would be silly to put the enable register
last or done some sort of strobe thing.

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