Messages in this thread | | | Date | Thu, 12 Jul 2012 12:56:31 +0200 | Subject | Re: [PATCH 33/36] AArch64: Generic timers support | From | Linus Walleij <> |
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On Thu, Jul 12, 2012 at 12:09 PM, Marc Zyngier <marc.zyngier@arm.com> wrote:
> On Thu, 12 Jul 2012 02:18:42 +0200, Linus Walleij > <linus.ml.walleij@gmail.com> wrote: > > Hi Linus, > >> I'm reviewing the only patch I really understand... >> >> 2012/7/6 Catalin Marinas <catalin.marinas@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
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