[PATCH] RTC: RK808: fix the rtc time reading issue

Sonny Rao sonnyrao at chromium.org
Wed Jan 14 11:44:02 PST 2015

On Wed, Jan 14, 2015 at 10:36 AM, Doug Anderson <dianders at chromium.org> wrote:
> Sonny,
>> Chris, it looks like you swapped the set and the clear of this bit,
>> and you're relying on the fact that the i2c transaction takes a
>> certain amount of time after the RTC_GET_TIME BIT is set.   I'm not
>> sure how long it actually takes, but why not just put in a usleep()
>> for the minimum wait time?
> I think we are safe.
> At 400kHz (the max speed of this part) each bit can be transferred no
> faster than 2.5us.  In order to do a valid i2c transaction we need to
> _at least_ write the address of the device and the data onto the bus,
> which is 16 bits.  16 * 2.5us = 40us.  That's above the 31.25us
> Personally I think what Chris has is fine, with the comment.

Ok, I'm fine with that if we're sure it's slow enough.  Comment
explaining would certainly help.

> -Doug

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