set_rtc_time() cleanup / normalization

[Wolfgang Denk]

In message <5.1.0.14.2.20030513161846.03805338 at mail.ebshome.net>
Eugene Surovegin wrote:
>
> >The consensus so far seems to be that we shouldn't call set_rtc_time
> >in the timer interrupt handler.  Is anyone willing to speak up with a
> >reason why we should keep it?
>
> Because there are systems which rely on this behavior?
> For example, all our embedded systems use this feature.
>
> Wolfgang said that "... many embedded systems run in a configuration
> where they use a high precision RTC chip...".
>
> All embedded systems I saw used cheap RTC parts with poor accuracy.
>
> I think we mix two different issues here:
>
> 1) call set_rtc_time() from timer interrupt every 11 min if clock is
> synched (e.g. by NTP)
>     I don't see any problems with this.

There are many problems with this approch, for a summary see
http://lists.linuxppc.org/linuxppc-dev/200305/msg00034.html

The main reason to remove it is thatit's broken (i. e. causes  kernel
crashes) on many hardware configurations.

> 2) set_rtc_time() implementation for concrete RTC device *maybe* slow or
> just cannot
>     be called from the interrupt context.
>     Why just don't fix actual RTC code in each case ?
>     It may be useful to provide some *generic* facility for such cases.

Do you have any recommendation HOW to implement such a "fix"?

The argument to put the set_rtc_time() call into the timer  interrupt
was  accuracy;  if  you  have to remove it from interrupt context the
only solution I've seen so far is to pay  for  an  additional  kernel
thread - more overhead, and you just removed the only argument to put
it into the timer interrupt at all.

It just makes no sense to me.

Best regards,

Wolfgang Denk

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