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

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Date:   Tue, 20 Aug 2019 13:33:14 -0500
From:   Li Yang <leoyang.li@....com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Alexandre Belloni <alexandre.belloni@...tlin.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 Tue, Aug 20, 2019 at 1:24 PM Mark Brown <broonie@...nel.org> wrote:
>
> On Fri, Aug 16, 2019 at 02:40:47PM -0500, Li Yang wrote:
> > On Fri, Aug 16, 2019 at 11:30 AM Alexandre Belloni
>
> > > Most of the i2c RTCs do address wrapping which is sometimes the only way
> > > to properly set the time.
>
> > Adding Mark and Nandor to the loop.
>
> Is there a specific question or something here?

Some of the RTC hardware has the capability of address wrapping which
means if you access a continuous address range across a certain
boundary(could be the boundary of a regmap region) the hardware
actually wrap the access to a lower address.  But the address
violation check of regmap rejects such access.  According to
Alexcandre, the address wrapping is essential to the functionality of
some RTC devices and can improve performance for some others.  We are
wondering if it is reasonable to have regmap support this address
wrapping.

Regards,
Leo