diff options
Diffstat (limited to 'arch/blackfin/kernel/time-ts.c')
| -rw-r--r-- | arch/blackfin/kernel/time-ts.c | 43 |
1 files changed, 9 insertions, 34 deletions
diff --git a/arch/blackfin/kernel/time-ts.c b/arch/blackfin/kernel/time-ts.c index 8c9a43daf80f..9e9b60d969dc 100644 --- a/arch/blackfin/kernel/time-ts.c +++ b/arch/blackfin/kernel/time-ts.c @@ -23,29 +23,6 @@ #include <asm/gptimers.h> #include <asm/nmi.h> -/* Accelerators for sched_clock() - * convert from cycles(64bits) => nanoseconds (64bits) - * basic equation: - * ns = cycles / (freq / ns_per_sec) - * ns = cycles * (ns_per_sec / freq) - * ns = cycles * (10^9 / (cpu_khz * 10^3)) - * ns = cycles * (10^6 / cpu_khz) - * - * Then we use scaling math (suggested by george@mvista.com) to get: - * ns = cycles * (10^6 * SC / cpu_khz) / SC - * ns = cycles * cyc2ns_scale / SC - * - * And since SC is a constant power of two, we can convert the div - * into a shift. - * - * We can use khz divisor instead of mhz to keep a better precision, since - * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits. - * (mathieu.desnoyers@polymtl.ca) - * - * -johnstul@us.ibm.com "math is hard, lets go shopping!" - */ - -#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */ #if defined(CONFIG_CYCLES_CLOCKSOURCE) @@ -63,7 +40,6 @@ static struct clocksource bfin_cs_cycles = { .rating = 400, .read = bfin_read_cycles, .mask = CLOCKSOURCE_MASK(64), - .shift = CYC2NS_SCALE_FACTOR, .flags = CLOCK_SOURCE_IS_CONTINUOUS, }; @@ -75,10 +51,7 @@ static inline unsigned long long bfin_cs_cycles_sched_clock(void) static int __init bfin_cs_cycles_init(void) { - bfin_cs_cycles.mult = \ - clocksource_hz2mult(get_cclk(), bfin_cs_cycles.shift); - - if (clocksource_register(&bfin_cs_cycles)) + if (clocksource_register_hz(&bfin_cs_cycles, get_cclk())) panic("failed to register clocksource"); return 0; @@ -111,7 +84,6 @@ static struct clocksource bfin_cs_gptimer0 = { .rating = 350, .read = bfin_read_gptimer0, .mask = CLOCKSOURCE_MASK(32), - .shift = CYC2NS_SCALE_FACTOR, .flags = CLOCK_SOURCE_IS_CONTINUOUS, }; @@ -125,10 +97,7 @@ static int __init bfin_cs_gptimer0_init(void) { setup_gptimer0(); - bfin_cs_gptimer0.mult = \ - clocksource_hz2mult(get_sclk(), bfin_cs_gptimer0.shift); - - if (clocksource_register(&bfin_cs_gptimer0)) + if (clocksource_register_hz(&bfin_cs_gptimer0, get_sclk())) panic("failed to register clocksource"); return 0; @@ -206,8 +175,14 @@ irqreturn_t bfin_gptmr0_interrupt(int irq, void *dev_id) { struct clock_event_device *evt = dev_id; smp_mb(); - evt->event_handler(evt); + /* + * We want to ACK before we handle so that we can handle smaller timer + * intervals. This way if the timer expires again while we're handling + * things, we're more likely to see that 2nd int rather than swallowing + * it by ACKing the int at the end of this handler. + */ bfin_gptmr0_ack(); + evt->event_handler(evt); return IRQ_HANDLED; } |