On Sat, Jan 06, 2007 at 03:52:43PM -0800, David Brownell wrote: > On Saturday 06 January 2007 3:26 pm, Philippe De Muyter wrote: > > On Fri, Jan 05, 2007 at 07:49:00PM -0800, David Brownell wrote: > > > > Those rtc's actually have a 1/100th of second > > > > register. Should the generic rtc interface not support that? > > > > > > Are you implying a new userspace API, or just an in-kernel update? > > > > My only concern at the moment is initializing linux's timeofday from the rtc > > quickly and with a good precision. > > There will necessarily be a bit of fuzz there since it can take time to > get that RTC's mutex, and the task setting that time can be preempted. > Plus, there can also be delays at the I2C or SPI transaction level. > > > > The way it is done currently > > in drivers/rtc/hctosys.c is 0.5 sec off. We could obtain a much better > > precision by looping there until the next change (next second for old > > clocks, > > next 0.01 second for m41t81, maybe even better for other ones). > > Hmm ... "looping" fights against "quickly"; as would "wait for next > update IRQ" (on RTCs that support that). But it would improve precision, > at least in the sense of having the system clock and that RTC spending > less time with the lowest "seconds" digit disagreeing. > > This is something you could write a patch for, n'est-ce pas?
That would require changing the interface provided by the rtc class, but I'll look at it. > > - Dave > > -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
