On Thu, Apr 17, 2008 at 11:14:00AM -0500, Scott Wood wrote:
> Anton Vorontsov wrote:
>> This isn't a timer with usec precision! This is a timer that silently
>> crops precision as it wants to. Ahh, I see you dropped "u" prefix.
>
> It is a timer with usec precision, unless you ask for a timeout of more
> than 65535 usec -- at which point the hardware can't provide usec
> precision.
>
> And s/as it wants to/as it needs to/.
>
>> Well. I'm not going to use it anyway, so just give it some name you
>> prefer and I'll wrap it into the patch. Preferably, drop a line here with
>> kerneldoc for it, so I'll not have to document its drawbacks. :-)
>
> /**
> * gtm_reset_timer16 - reset 16 bit timer with arbitrary precision
> * @tmr: pointer to the gtm_timer structure obtained from gtm_get_timer
> * @usec: timer interval in microseconds
> * @reload: if set, the timer will reset upon expiry rather than
> * continue running free.
> *
> * This function (re)sets the GTM timer so that it counts up to the
> * requested interval value, and fires the interrupt when the value is
> * reached. This function will reduce the precision of the timer as
> * needed in order for the requested timeout to fit in a 16-bit
> * register.
> */
> int gtm_reset_timer16(struct gtm_timer *tmr, unsigned long usec,
> bool reload)
> {
> ...
> }
Thanks!
>>> It could be made faster using cntlzw.
>>
>> No need to cntlzw, there is fls() already.
>
> fls() uses cntlzw, does it not? I was just too lazy to look up what
> Linux calls it. :-)
Yup, I looked it up. ;-)
>> Though, here you'll need two because of u64.
>
> We can probably get away with 32 bits.
>
>> Btw, I hope you aware that single GTM timer running at 166MHz will give you
>> 6 minutes of sleep, maximum.
>
> Yes, but it's all we have on-chip that can do the job.
>
>> With cascaded timer you'll get much better
>> result of 310 days. Is that possible to use cascaded timer as a wakeup
>> event on 8313?
>
> No, unfortunately. Only timer4 can be a wakeup source, and when
> cascaded, timer4 is the input to timer3, rather than the other way
> around.
Ok, very well.
--
Anton Vorontsov
email: [EMAIL PROTECTED]
irc://irc.freenode.net/bd2
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