On Tue, May 20, 2008 at 09:20:50AM -0500, Kumar Gala wrote: >>>>> This is explained in the .c file with a kernel doc. Basically the >>>> difference is that timer16 could silently crop the precision, while >>>> utimer16 could not thus explicitly accepts u16 argument (max. timer >>>> interval with usec precision fits in u16). >>> >>> Maybe I'm confused what the utility is of cropping the precision in >>> this >>> way is. I'd also say that _timer16 is poorly named to convey the >>> behavior. I'm not sure what to call it because I still dont get >>> exactly >>> why you'd want the precision cropped. >> >> Precision matters for FHCI-like drivers, when driver, for example, >> schedule transactions via the GTM timers, and there timings matters >> a lot. >> >> Though, timer16 crops the precision _only_ if usecs > 65535, so FHCI >> _can_ still use the _timer16 (because FHCI does not request intervals >>> 65535). But I implemented two function because: >> >> 1. I think we don't need unnecessary stuff in the ISRs (this is weak >> argument since I didn't measure the impact). >> 2. I wanted to make the API clear (seem to fail this undertaking :-), >> which functions will behave exactly the way you asked it (utimer16), >> and which functions will _silently_ crop the precision (timer16) >> (if asked for 1001000 usecs, it will give you ~~1001000, depending >> on the GTM frequency). > > I'm fine w/having both. I think they are poorly named. I'd also call > them _set_timer but that's just me. > > Maybe something w/the term _exact_ in the name. Is it the case w/the > precise form we'd have no prescaling (if so maybe a comment in the API > about that would help clarity)?
We're always prescale [to 1000000 MHz for usec precision]. Otherwise these functions would be non-deterministic (will purely depend on the GTM frequency, so "usec" argument would not have defined boundaries). -- Anton Vorontsov email: [EMAIL PROTECTED] irc://irc.freenode.net/bd2 _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
