Re: [PATCH 4.4.y-cip 03/10] rtc: pcf85363: set time accurately


Biju Das <biju.das@...>
 

Hi Pavel,

Thanks for the feedback.

-----Original Message-----
From: Pavel Machek <pavel@...>
Sent: Tuesday, July 16, 2019 10:04 PM
To: Biju Das <biju.das@...>
Cc: cip-dev@...
Subject: Re: [cip-dev] [PATCH 4.4.y-cip 03/10] rtc: pcf85363: set time
accurately

On Tue 2019-07-16 09:15:14, Biju Das wrote:
commit 188306ac9536ec47674ffa9dd330f69927679aeb upstream.

As per 8.2.6 Setting and reading the time in RTC mode, first stop the
clok, then reset it before setting the date and time registers.
Finally, start the clock.

This uses register address wrap around from 0x2f to 0x00 for
efficiency.
How does wrap around work? AFAICT it is supposed to have ram at 0x40.
Please see the document [1] and [2] section 8, that have the details related to wrap around.
[1] https://www.nxp.com/docs/en/data-sheet/PCF85363A.pdf
[2] https://www.nxp.com/docs/en/data-sheet/PCF85263A.pdf

Regards,
Biju

Does it really provide increased efficiency (given regmap layer in
between) and will such trick cause problems in future? If regmap is not
aware of register mirrors it might get confused and provide stale values, for
example...

Best regards,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures)
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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