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authorNicolas Pitre <nico@cam.org>2006-12-04 20:42:09 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2006-12-07 16:06:55 +0000
commit2dc20a51dc1e2da6eae1182cfe4c4835fca26017 (patch)
tree206a73320b1d41451884f0ca5d0796af9a34c50e /arch/arm/mach-pxa
parent752bee178ee107aa3dd87a9aeba970444034c6fb (diff)
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[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/mach-pxa')
-rw-r--r--arch/arm/mach-pxa/generic.c60
1 files changed, 60 insertions, 0 deletions
diff --git a/arch/arm/mach-pxa/generic.c b/arch/arm/mach-pxa/generic.c
index 45fb2c3..6ae6058 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
*/