On Thu, Jul 12, 2012 at 12:09 PM, Marc Zyngier <marc.zyng...@arm.com> wrote:
> On Thu, 12 Jul 2012 02:18:42 +0200, Linus Walleij > <linus.ml.wall...@gmail.com> wrote: > > Hi Linus, > >> I'm reviewing the only patch I really understand... >> >> 2012/7/6 Catalin Marinas <catalin.mari...@arm.com>: >> >>> +/* This isn't really used any more */ >>> +#define CLOCK_TICK_RATE 1000 >> >> Is it still necessary to even have it there? > > It is used as part of the LATCH/TICK_* computation in > include/linux/jiffies.h. It seems that any value could do, actually, and it > only seem to be used in kernel/time/ntp.c. Any guidance on this much > appreciated. > > By the way, there is a very interesting comment about this in > arch/ia64/include/asm/timex.h. Hmmmm paging John Stultz, TGLX, Deepak Saxena who have been in this area... >>> + arch_timer_calibrate(); >> >> Why is the ability to get this from a clk not contemplated? >> I think this will be common. You could make it optional I think, >> just like in the SMP TWD. > > _calibrate() is a misnomer here. It should really be _get_freq(). But your > point still stand, and we could indeed use a clk to obtain the frequency. > > It should probably be selected in the following order: clock-frequency > (DT), clk, CNTFRQ. I agree. It can be bolted on later too, just trying to think ahead a bit. I'm half-guessing that for mobile embedded with their complex clock trees it will likely come from a clk whereas in servers etc there will be one big clock for all and it will be fine to use the DT node. Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
