Re: sparc generic time / clockevents
From: David Miller
Date: Fri Feb 23 2007 - 19:34:48 EST
From: john stultz <johnstul@xxxxxxxxxx>
Date: Fri, 23 Feb 2007 11:51:18 -0800
> Yea. I actually have some in-progress patches from Peter Keilty that
> convert ia64 and sparc64 time_interpolators to clocksources, then
> removes the time_interpolator code.
> The ia64 conversion is more complicated due to the fsyscall asm, but I
> think the sparc64 conversion (below) is pretty straight forward. I've
> only built tested this, so I have no clue if it actually works.
> Any thoughts?
Hey John, I had to do this already in order to do the dynticks
port to sparc64, but nice to see another attempt :-)
Two things I did on my side:
+ .mask = 0xffffffffffffffffLL,
I used CLOCKSOURCE_MASK(64) here.
+static cycle_t read_sparc64_cpuclock(void)
+ return (cycle_t)get_cycles();
+ .read = read_sparc64_cpuclock,
You can just directly assign tick_ops->get_tick to .read at run-time
to avoid a stack frame and function call/return.
+ .shift = 16,
These shift selections all seem rather arbitrary.
If it's not an arbitrary selection, it would be nice to have some
comments about how to go about choosing an appropriate shift.
I imagine the selections has to do with the possible range of
the frequencies the clocksource supports, and how much
accuracy you get for certain shift selections given that range.
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