diff options
Diffstat (limited to 'arch/mn10300/kernel/time.c')
| -rw-r--r-- | arch/mn10300/kernel/time.c | 52 |
1 files changed, 41 insertions, 11 deletions
diff --git a/arch/mn10300/kernel/time.c b/arch/mn10300/kernel/time.c index babb7c2ac377..e4606586f94c 100644 --- a/arch/mn10300/kernel/time.c +++ b/arch/mn10300/kernel/time.c @@ -1,6 +1,6 @@ /* MN10300 Low level time management * - * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved. + * Copyright (C) 2007-2008 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * - Derived from arch/i386/kernel/time.c * @@ -16,6 +16,7 @@ #include <linux/init.h> #include <linux/smp.h> #include <linux/profile.h> +#include <linux/cnt32_to_63.h> #include <asm/irq.h> #include <asm/div64.h> #include <asm/processor.h> @@ -40,27 +41,54 @@ static struct irqaction timer_irq = { .name = "timer", }; +static unsigned long sched_clock_multiplier; + /* * scheduler clock - returns current time in nanosec units. */ unsigned long long sched_clock(void) { union { - unsigned long long l; - u32 w[2]; - } quot; + unsigned long long ll; + unsigned l[2]; + } tsc64, result; + unsigned long tsc, tmp; + unsigned product[3]; /* 96-bit intermediate value */ + + /* read the TSC value + */ + tsc = 0 - get_cycles(); /* get_cycles() counts down */ - quot.w[0] = mn10300_last_tsc - get_cycles(); - quot.w[1] = 1000000000; + /* expand to 64-bits. + * - sched_clock() must be called once a minute or better or the + * following will go horribly wrong - see cnt32_to_63() + */ + tsc64.ll = cnt32_to_63(tsc) & 0x7fffffffffffffffULL; - asm("mulu %2,%3,%0,%1" - : "=r"(quot.w[1]), "=r"(quot.w[0]) - : "0"(quot.w[1]), "1"(quot.w[0]) + /* scale the 64-bit TSC value to a nanosecond value via a 96-bit + * intermediate + */ + asm("mulu %2,%0,%3,%0 \n" /* LSW * mult -> 0:%3:%0 */ + "mulu %2,%1,%2,%1 \n" /* MSW * mult -> %2:%1:0 */ + "add %3,%1 \n" + "addc 0,%2 \n" /* result in %2:%1:%0 */ + : "=r"(product[0]), "=r"(product[1]), "=r"(product[2]), "=r"(tmp) + : "0"(tsc64.l[0]), "1"(tsc64.l[1]), "2"(sched_clock_multiplier) : "cc"); - do_div(quot.l, MN10300_TSCCLK); + result.l[0] = product[1] << 16 | product[0] >> 16; + result.l[1] = product[2] << 16 | product[1] >> 16; - return quot.l; + return result.ll; +} + +/* + * initialise the scheduler clock + */ +static void __init mn10300_sched_clock_init(void) +{ + sched_clock_multiplier = + __muldiv64u(NSEC_PER_SEC, 1 << 16, MN10300_TSCCLK); } /* @@ -128,4 +156,6 @@ void __init time_init(void) /* start the watchdog timer */ watchdog_go(); #endif + + mn10300_sched_clock_init(); } |