From 2dc20a51dc1e2da6eae1182cfe4c4835fca26017 Mon Sep 17 00:00:00 2001 From: Nicolas Pitre Date: Mon, 4 Dec 2006 20:42:09 +0100 Subject: [PATCH] [ARM] 3981/1: sched_clock for PXA2xx Here's a 63-bit implementation of shed_clock() for PXA2xx. The actual period depends on the value of CLOCK_TICK_RATE and whether or not reduced scaling factors were provided for it. Signed-off-by: Nicolas Pitre Signed-off-by: Russell King --- arch/arm/mach-pxa/generic.c | 60 +++++++++++++++++++++++++++++++++++++ 1 file changed, 60 insertions(+) diff --git a/arch/arm/mach-pxa/generic.c b/arch/arm/mach-pxa/generic.c index 45fb2c3bcf..6ae605857c 100644 --- a/arch/arm/mach-pxa/generic.c +++ b/arch/arm/mach-pxa/generic.c @@ -25,6 +25,10 @@ #include #include +#include +#include +#include + #include #include #include @@ -40,6 +44,62 @@ #include "generic.h" +/* + * This is the PXA2xx sched_clock implementation. This has a resolution + * of at least 308ns and a maximum value that depends on the value of + * CLOCK_TICK_RATE. + * + * The return value is guaranteed to be monotonic in that range as + * long as there is always less than 582 seconds between successive + * calls to this function. + */ +unsigned long long sched_clock(void) +{ + unsigned long long v = cnt32_to_63(OSCR); + /* Note: top bit ov v needs cleared unless multiplier is even. */ + +#if CLOCK_TICK_RATE == 3686400 + /* 1E9 / 3686400 => 78125 / 288, max value = 32025597s (370 days). */ + /* The <<1 is used to get rid of tick.hi top bit */ + v *= 78125<<1; + do_div(v, 288<<1); +#elif CLOCK_TICK_RATE == 3250000 + /* 1E9 / 3250000 => 4000 / 13, max value = 709490156s (8211 days) */ + v *= 4000; + do_div(v, 13); +#elif CLOCK_TICK_RATE == 3249600 + /* 1E9 / 3249600 => 625000 / 2031, max value = 4541295s (52 days) */ + v *= 625000; + do_div(v, 2031); +#else +#warning "consider fixing sched_clock for your value of CLOCK_TICK_RATE" + /* + * 96-bit math to perform tick * NSEC_PER_SEC / CLOCK_TICK_RATE for + * any value of CLOCK_TICK_RATE. Max value is in the 80 thousand + * years range which is nice, but with higher computation cost. + */ + { + union { + unsigned long long val; + struct { unsigned long lo, hi; }; + } x; + unsigned long long y; + + x.val = v; + x.hi &= 0x7fffffff; + y = (unsigned long long)x.lo * NSEC_PER_SEC; + x.lo = y; + y = (y >> 32) + (unsigned long long)x.hi * NSEC_PER_SEC; + x.hi = do_div(y, CLOCK_TICK_RATE); + do_div(x.val, CLOCK_TICK_RATE); + x.hi += y; + v = x.val; + } +#endif + + return v; +} + /* * Handy function to set GPIO alternate functions */ -- 2.39.5