MN10300: Make sched_clock() report time since boot
Make sched_clock() report time since boot rather than time since last timer interrupt. Make sched_clock() expand and scale the 32-bit TSC value running at IOCLK speed (~33MHz) to a 64-bit nanosecond counter, using cnt32_to_63() acquired from the ARM arch and without using slow DIVU instructions every call. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -1,6 +1,6 @@
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/* MN10300 Low level time management
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*
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* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
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* Copyright (C) 2007-2008 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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* - Derived from arch/i386/kernel/time.c
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*
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@ -16,6 +16,7 @@
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#include <linux/init.h>
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#include <linux/smp.h>
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#include <linux/profile.h>
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#include <linux/cnt32_to_63.h>
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#include <asm/irq.h>
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#include <asm/div64.h>
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#include <asm/processor.h>
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@ -40,27 +41,54 @@ static struct irqaction timer_irq = {
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.name = "timer",
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};
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static unsigned long sched_clock_multiplier;
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/*
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* scheduler clock - returns current time in nanosec units.
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*/
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unsigned long long sched_clock(void)
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{
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union {
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unsigned long long l;
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u32 w[2];
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} quot;
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unsigned long long ll;
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unsigned l[2];
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} tsc64, result;
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unsigned long tsc, tmp;
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unsigned product[3]; /* 96-bit intermediate value */
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quot.w[0] = mn10300_last_tsc - get_cycles();
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quot.w[1] = 1000000000;
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/* read the TSC value
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*/
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tsc = 0 - get_cycles(); /* get_cycles() counts down */
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asm("mulu %2,%3,%0,%1"
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: "=r"(quot.w[1]), "=r"(quot.w[0])
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: "0"(quot.w[1]), "1"(quot.w[0])
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/* expand to 64-bits.
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* - sched_clock() must be called once a minute or better or the
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* following will go horribly wrong - see cnt32_to_63()
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*/
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tsc64.ll = cnt32_to_63(tsc) & 0x7fffffffffffffffULL;
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/* scale the 64-bit TSC value to a nanosecond value via a 96-bit
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* intermediate
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*/
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asm("mulu %2,%0,%3,%0 \n" /* LSW * mult -> 0:%3:%0 */
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"mulu %2,%1,%2,%1 \n" /* MSW * mult -> %2:%1:0 */
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"add %3,%1 \n"
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"addc 0,%2 \n" /* result in %2:%1:%0 */
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: "=r"(product[0]), "=r"(product[1]), "=r"(product[2]), "=r"(tmp)
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: "0"(tsc64.l[0]), "1"(tsc64.l[1]), "2"(sched_clock_multiplier)
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: "cc");
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do_div(quot.l, MN10300_TSCCLK);
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result.l[0] = product[1] << 16 | product[0] >> 16;
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result.l[1] = product[2] << 16 | product[1] >> 16;
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return quot.l;
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return result.ll;
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}
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/*
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* initialise the scheduler clock
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*/
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static void __init mn10300_sched_clock_init(void)
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{
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sched_clock_multiplier =
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__muldiv64u(NSEC_PER_SEC, 1 << 16, MN10300_TSCCLK);
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}
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/*
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@ -128,4 +156,6 @@ void __init time_init(void)
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/* start the watchdog timer */
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watchdog_go();
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#endif
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mn10300_sched_clock_init();
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}
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