diff options
| author | Nicolas Pitre <nico@cam.org> | 2006-12-04 20:42:09 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2006-12-07 16:06:55 +0000 |
| commit | 2dc20a51dc1e2da6eae1182cfe4c4835fca26017 (patch) | |
| tree | 206a73320b1d41451884f0ca5d0796af9a34c50e /arch/arm | |
| parent | 752bee178ee107aa3dd87a9aeba970444034c6fb (diff) | |
[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 <nico@cam.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm')
| -rw-r--r-- | arch/arm/mach-pxa/generic.c | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/arch/arm/mach-pxa/generic.c b/arch/arm/mach-pxa/generic.c index 45fb2c3bcf82..6ae605857ca9 100644 --- a/arch/arm/mach-pxa/generic.c +++ b/arch/arm/mach-pxa/generic.c @@ -25,6 +25,10 @@ #include <linux/pm.h> #include <linux/string.h> +#include <linux/sched.h> +#include <asm/cnt32_to_63.h> +#include <asm/div64.h> + #include <asm/hardware.h> #include <asm/irq.h> #include <asm/system.h> @@ -41,6 +45,62 @@ #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 */ |