diff options
Diffstat (limited to 'arch/arm/plat-orion/time.c')
| -rw-r--r-- | arch/arm/plat-orion/time.c | 59 |
1 files changed, 58 insertions, 1 deletions
diff --git a/arch/arm/plat-orion/time.c b/arch/arm/plat-orion/time.c index de8a001fc3a..715a30177f2 100644 --- a/arch/arm/plat-orion/time.c +++ b/arch/arm/plat-orion/time.c @@ -12,11 +12,15 @@ */ #include <linux/kernel.h> +#include <linux/sched.h> +#include <linux/cnt32_to_63.h> +#include <linux/timer.h> #include <linux/clockchips.h> #include <linux/interrupt.h> #include <linux/irq.h> #include <asm/mach/time.h> #include <mach/bridge-regs.h> +#include <mach/hardware.h> /* * Number of timer ticks per jiffy. @@ -39,6 +43,56 @@ static u32 ticks_per_jiffy; /* + * Orion's sched_clock implementation. It has a resolution of + * at least 7.5ns (133MHz TCLK) and a maximum value of 834 days. + * + * Because the hardware timer period is quite short (21 secs if + * 200MHz TCLK) and because cnt32_to_63() needs to be called at + * least once per half period to work properly, a kernel timer is + * set up to ensure this requirement is always met. + */ +#define TCLK2NS_SCALE_FACTOR 8 + +static unsigned long tclk2ns_scale; + +unsigned long long sched_clock(void) +{ + unsigned long long v = cnt32_to_63(0xffffffff - readl(TIMER0_VAL)); + return (v * tclk2ns_scale) >> TCLK2NS_SCALE_FACTOR; +} + +static struct timer_list cnt32_to_63_keepwarm_timer; + +static void cnt32_to_63_keepwarm(unsigned long data) +{ + mod_timer(&cnt32_to_63_keepwarm_timer, round_jiffies(jiffies + data)); + (void) sched_clock(); +} + +static void __init setup_sched_clock(unsigned long tclk) +{ + unsigned long long v; + unsigned long data; + + v = NSEC_PER_SEC; + v <<= TCLK2NS_SCALE_FACTOR; + v += tclk/2; + do_div(v, tclk); + /* + * We want an even value to automatically clear the top bit + * returned by cnt32_to_63() without an additional run time + * instruction. So if the LSB is 1 then round it up. + */ + if (v & 1) + v++; + tclk2ns_scale = v; + + data = (0xffffffffUL / tclk / 2 - 2) * HZ; + setup_timer(&cnt32_to_63_keepwarm_timer, cnt32_to_63_keepwarm, data); + mod_timer(&cnt32_to_63_keepwarm_timer, round_jiffies(jiffies + data)); +} + +/* * Clocksource handling. */ static cycle_t orion_clksrc_read(struct clocksource *cs) @@ -176,6 +230,10 @@ void __init orion_time_init(unsigned int irq, unsigned int tclk) ticks_per_jiffy = (tclk + HZ/2) / HZ; + /* + * Set scale and timer for sched_clock + */ + setup_sched_clock(tclk); /* * Setup free-running clocksource timer (interrupts @@ -190,7 +248,6 @@ void __init orion_time_init(unsigned int irq, unsigned int tclk) orion_clksrc.mult = clocksource_hz2mult(tclk, orion_clksrc.shift); clocksource_register(&orion_clksrc); - /* * Setup clockevent timer (interrupt-driven.) */ |