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SubjectRe: RTC: add RTC class interface to m41t00 driver
Hi Atsushi,
Hi David,

I've seen very late that the rtc-ds1307.c driver supports the quite
simple m41t00 as well. As Mark's m41t00.c claimed to support even the
m41t81 and the m41st85, I startet at this point.

First, I sent my approach to Mark (m41t00.c), Alessandro (rtc-subsytem)
and Jean (i2c-subsystem) to discuss the strategy. And if I understood
them right, they found the idea good, to move the i2c/chips/m41t00.h to
an rtc/rtc-m41txx.c driver, as this should be the general place for such
rtc-drivers.

As Atsushi has done almost the same work, I postet my version on friday
to pretend the next person to do this job and to start the discussion,
how to get to a suitable version for all - including Mark with his
arch/ppc/platforms/katana.c boards.

I confirm, that the rtc-ds1307.c driver works with m41t00. But the
m41t8x or m41st8x differs a lot from the m41t00 (HT bit, ST bit, SQW
freq - like Atsushi wrote it already).


Atsushi Nemoto wrote:
> 2. As m41t00_chip_info_tbl[] in m41t00 driver shows, M41T81 and M41T85
> have different register layout.
>

The register layout seems to depend on the watchdog and alarm
functionality.
The features differs from chip to chip, that's why I intodruced a
"features"-field in struct m41txx_chip_info.

> 3. It lacks some features (ST bit, HT bit, SQW freq.) in m41t00
> driver, though I personally does not need these features.
>

You need at least to clear the Stop Bit (ST) and the Halt Update Bit
(HT) unless your m41t8x will always report the time of the last power
fail and not the current time.

For me there is still the open question, if the workqueue-part and the
exported symbols (m41t00_get_rtc_time, ) should stay or not. I don't
need it and Atsushi seems to share my opinion. But...?

On monday, I can continue work on it.


Alexander

--
Alexander Bigga Tel: +49 4873 90 10 866
mycable GmbH Fax: +49 4873 90 19 76
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D-24613 Aukrug eMail: ab@mycable.de


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