Benjamin Herrenschmidt wrote:
>>>Allow generic_calibrate_decr to work for 40x platforms. Given that the
>>>hardware
>>>behavior is identical, this also changes the set_dec function to reload the
>>>PIT
>>>on 40x to match the behavior 44x currently has.
>> Why bother doing this?! This will only warrant you imprecise decrementer
>>interrupts while it should be interrupting at the precise period currently
>>(if
>>you load PIT once)...
> Because that's what the kernel timekeeping code expects ? The reference
> time is the timebase and it doesn't drift.
> The DEC/PIT is commonly used to trigger any timing, such as what is done
> for lost interrupts on some platforms. Also, with dynticks, we'll most
> certainly want variable reload values as well.
That's another matter. :-)
BTW, because of that mere return in set_dec() for the 40x case I had to
write to the PIT myself in the decrementer clockevent's set_next_event()
method -- while for classic PPC I was just calling set_dec(n-1)...
> So I'm very happy to have Josh change the code that way. It makes things
> more consistent accross the board and removes confusion.
Yeah, it's OK now that's my temporary confusion has passed.
Well, it wasn't only not only mine -- the set_dec() code was suggesting
auto-reload mode, and has been obviosuly copied from <asm-ppc/time.h>, so
arch/ppc/ was using the auto-reload mode indeed.
> Ben.
WBR, Sergei
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