diff options
Diffstat (limited to 'arch/parisc/kernel/time.c')
| -rw-r--r-- | arch/parisc/kernel/time.c | 63 |
1 files changed, 62 insertions, 1 deletions
diff --git a/arch/parisc/kernel/time.c b/arch/parisc/kernel/time.c index 400acac0a304..58dd6801f5be 100644 --- a/arch/parisc/kernel/time.c +++ b/arch/parisc/kernel/time.c @@ -38,6 +38,18 @@ static unsigned long clocktick __read_mostly; /* timer cycles per tick */ +#ifndef CONFIG_64BIT +/* + * The processor-internal cycle counter (Control Register 16) is used as time + * source for the sched_clock() function. This register is 64bit wide on a + * 64-bit kernel and 32bit on a 32-bit kernel. Since sched_clock() always + * requires a 64bit counter we emulate on the 32-bit kernel the higher 32bits + * with a per-cpu variable which we increase every time the counter + * wraps-around (which happens every ~4 secounds). + */ +static DEFINE_PER_CPU(unsigned long, cr16_high_32_bits); +#endif + /* * We keep time on PA-RISC Linux by using the Interval Timer which is * a pair of registers; one is read-only and one is write-only; both @@ -108,6 +120,12 @@ irqreturn_t __irq_entry timer_interrupt(int irq, void *dev_id) */ mtctl(next_tick, 16); +#if !defined(CONFIG_64BIT) + /* check for overflow on a 32bit kernel (every ~4 seconds). */ + if (unlikely(next_tick < now)) + this_cpu_inc(cr16_high_32_bits); +#endif + /* Skip one clocktick on purpose if we missed next_tick. * The new CR16 must be "later" than current CR16 otherwise * itimer would not fire until CR16 wrapped - e.g 4 seconds @@ -219,6 +237,12 @@ void __init start_cpu_itimer(void) unsigned int cpu = smp_processor_id(); unsigned long next_tick = mfctl(16) + clocktick; +#if defined(CONFIG_HAVE_UNSTABLE_SCHED_CLOCK) && defined(CONFIG_64BIT) + /* With multiple 64bit CPUs online, the cr16's are not syncronized. */ + if (cpu != 0) + clear_sched_clock_stable(); +#endif + mtctl(next_tick, 16); /* kick off Interval Timer (CR16) */ per_cpu(cpu_data, cpu).it_value = next_tick; @@ -246,15 +270,52 @@ void read_persistent_clock(struct timespec *ts) } } + +/* + * sched_clock() framework + */ + +static u32 cyc2ns_mul __read_mostly; +static u32 cyc2ns_shift __read_mostly; + +u64 sched_clock(void) +{ + u64 now; + + /* Get current cycle counter (Control Register 16). */ +#ifdef CONFIG_64BIT + now = mfctl(16); +#else + now = mfctl(16) + (((u64) this_cpu_read(cr16_high_32_bits)) << 32); +#endif + + /* return the value in ns (cycles_2_ns) */ + return mul_u64_u32_shr(now, cyc2ns_mul, cyc2ns_shift); +} + + +/* + * timer interrupt and sched_clock() initialization + */ + void __init time_init(void) { unsigned long current_cr16_khz; + current_cr16_khz = PAGE0->mem_10msec/10; /* kHz */ clocktick = (100 * PAGE0->mem_10msec) / HZ; + /* calculate mult/shift values for cr16 */ + clocks_calc_mult_shift(&cyc2ns_mul, &cyc2ns_shift, current_cr16_khz, + NSEC_PER_MSEC, 0); + +#if defined(CONFIG_HAVE_UNSTABLE_SCHED_CLOCK) && defined(CONFIG_64BIT) + /* At bootup only one 64bit CPU is online and cr16 is "stable" */ + set_sched_clock_stable(); +#endif + start_cpu_itimer(); /* get CPU 0 started */ /* register at clocksource framework */ - current_cr16_khz = PAGE0->mem_10msec/10; /* kHz */ clocksource_register_khz(&clocksource_cr16, current_cr16_khz); } |