Re: RTC: add RTC class interface to m41t00 driver

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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

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