diff options
| -rw-r--r-- | arch/i386/kernel/timers/common.c | 9 | ||||
| -rw-r--r-- | arch/i386/kernel/timers/timer.c | 9 | ||||
| -rw-r--r-- | arch/i386/kernel/timers/timer_hpet.c | 1 | ||||
| -rw-r--r-- | arch/i386/kernel/timers/timer_pm.c | 1 | ||||
| -rw-r--r-- | arch/i386/kernel/timers/timer_tsc.c | 1 | ||||
| -rw-r--r-- | arch/x86_64/lib/delay.c | 7 | ||||
| -rw-r--r-- | include/asm-i386/timer.h | 2 | ||||
| -rw-r--r-- | include/asm-i386/timex.h | 3 | ||||
| -rw-r--r-- | include/asm-x86_64/timex.h | 3 | ||||
| -rw-r--r-- | init/calibrate.c | 94 |
10 files changed, 130 insertions, 0 deletions
diff --git a/arch/i386/kernel/timers/common.c b/arch/i386/kernel/timers/common.c index 8e20121..b38cc0d 100644 --- a/arch/i386/kernel/timers/common.c +++ b/arch/i386/kernel/timers/common.c @@ -139,6 +139,15 @@ bad_calibration: } #endif + +unsigned long read_timer_tsc(void) +{ + unsigned long retval; + rdtscl(retval); + return retval; +} + + /* calculate cpu_khz */ void init_cpu_khz(void) { diff --git a/arch/i386/kernel/timers/timer.c b/arch/i386/kernel/timers/timer.c index a3d6a28..7e39ed8 100644 --- a/arch/i386/kernel/timers/timer.c +++ b/arch/i386/kernel/timers/timer.c @@ -64,3 +64,12 @@ struct timer_opts* __init select_timer(void) panic("select_timer: Cannot find a suitable timer\n"); return NULL; } + +int read_current_timer(unsigned long *timer_val) +{ + if (cur_timer->read_timer) { + *timer_val = cur_timer->read_timer(); + return 0; + } + return -1; +} diff --git a/arch/i386/kernel/timers/timer_hpet.c b/arch/i386/kernel/timers/timer_hpet.c index f778f47..15a7d72 100644 --- a/arch/i386/kernel/timers/timer_hpet.c +++ b/arch/i386/kernel/timers/timer_hpet.c @@ -186,6 +186,7 @@ static struct timer_opts timer_hpet = { .get_offset = get_offset_hpet, .monotonic_clock = monotonic_clock_hpet, .delay = delay_hpet, + .read_timer = read_timer_tsc, }; struct init_timer_opts __initdata timer_hpet_init = { diff --git a/arch/i386/kernel/timers/timer_pm.c b/arch/i386/kernel/timers/timer_pm.c index d77f220..4ef20e6 100644 --- a/arch/i386/kernel/timers/timer_pm.c +++ b/arch/i386/kernel/timers/timer_pm.c @@ -246,6 +246,7 @@ static struct timer_opts timer_pmtmr = { .get_offset = get_offset_pmtmr, .monotonic_clock = monotonic_clock_pmtmr, .delay = delay_pmtmr, + .read_timer = read_timer_tsc, }; struct init_timer_opts __initdata timer_pmtmr_init = { diff --git a/arch/i386/kernel/timers/timer_tsc.c b/arch/i386/kernel/timers/timer_tsc.c index 180444d..27f08ae 100644 --- a/arch/i386/kernel/timers/timer_tsc.c +++ b/arch/i386/kernel/timers/timer_tsc.c @@ -572,6 +572,7 @@ static struct timer_opts timer_tsc = { .get_offset = get_offset_tsc, .monotonic_clock = monotonic_clock_tsc, .delay = delay_tsc, + .read_timer = read_timer_tsc, }; struct init_timer_opts __initdata timer_tsc_init = { diff --git a/arch/x86_64/lib/delay.c b/arch/x86_64/lib/delay.c index aed61a6..33a873a 100644 --- a/arch/x86_64/lib/delay.c +++ b/arch/x86_64/lib/delay.c @@ -12,6 +12,7 @@ #include <linux/sched.h> #include <linux/delay.h> #include <asm/delay.h> +#include <asm/msr.h> #ifdef CONFIG_SMP #include <asm/smp.h> @@ -19,6 +20,12 @@ int x86_udelay_tsc = 0; /* Delay via TSC */ +int read_current_timer(unsigned long *timer_value) +{ + rdtscll(*timer_value); + return 0; +} + void __delay(unsigned long loops) { unsigned bclock, now; diff --git a/include/asm-i386/timer.h b/include/asm-i386/timer.h index c347098..dcf1e07 100644 --- a/include/asm-i386/timer.h +++ b/include/asm-i386/timer.h @@ -22,6 +22,7 @@ struct timer_opts { unsigned long (*get_offset)(void); unsigned long long (*monotonic_clock)(void); void (*delay)(unsigned long); + unsigned long (*read_timer)(void); }; struct init_timer_opts { @@ -52,6 +53,7 @@ extern struct init_timer_opts timer_cyclone_init; #endif extern unsigned long calibrate_tsc(void); +extern unsigned long read_timer_tsc(void); extern void init_cpu_khz(void); extern int recalibrate_cpu_khz(void); #ifdef CONFIG_HPET_TIMER diff --git a/include/asm-i386/timex.h b/include/asm-i386/timex.h index b41e484..e370f90 100644 --- a/include/asm-i386/timex.h +++ b/include/asm-i386/timex.h @@ -49,4 +49,7 @@ static inline cycles_t get_cycles (void) extern unsigned long cpu_khz; +extern int read_current_timer(unsigned long *timer_value); +#define ARCH_HAS_READ_CURRENT_TIMER 1 + #endif diff --git a/include/asm-x86_64/timex.h b/include/asm-x86_64/timex.h index 34f31a1..24ecf6a 100644 --- a/include/asm-x86_64/timex.h +++ b/include/asm-x86_64/timex.h @@ -26,6 +26,9 @@ static inline cycles_t get_cycles (void) extern unsigned int cpu_khz; +extern int read_current_timer(unsigned long *timer_value); +#define ARCH_HAS_READ_CURRENT_TIMER 1 + extern struct vxtime_data vxtime; #endif diff --git a/init/calibrate.c b/init/calibrate.c index c698e04..d206c75 100644 --- a/init/calibrate.c +++ b/init/calibrate.c @@ -8,6 +8,8 @@ #include <linux/delay.h> #include <linux/init.h> +#include <asm/timex.h> + static unsigned long preset_lpj; static int __init lpj_setup(char *str) { @@ -17,6 +19,92 @@ static int __init lpj_setup(char *str) __setup("lpj=", lpj_setup); +#ifdef ARCH_HAS_READ_CURRENT_TIMER + +/* This routine uses the read_current_timer() routine and gets the + * loops per jiffy directly, instead of guessing it using delay(). + * Also, this code tries to handle non-maskable asynchronous events + * (like SMIs) + */ +#define DELAY_CALIBRATION_TICKS ((HZ < 100) ? 1 : (HZ/100)) +#define MAX_DIRECT_CALIBRATION_RETRIES 5 + +static unsigned long __devinit calibrate_delay_direct(void) +{ + unsigned long pre_start, start, post_start; + unsigned long pre_end, end, post_end; + unsigned long start_jiffies; + unsigned long tsc_rate_min, tsc_rate_max; + unsigned long good_tsc_sum = 0; + unsigned long good_tsc_count = 0; + int i; + + if (read_current_timer(&pre_start) < 0 ) + return 0; + + /* + * A simple loop like + * while ( jiffies < start_jiffies+1) + * start = read_current_timer(); + * will not do. As we don't really know whether jiffy switch + * happened first or timer_value was read first. And some asynchronous + * event can happen between these two events introducing errors in lpj. + * + * So, we do + * 1. pre_start <- When we are sure that jiffy switch hasn't happened + * 2. check jiffy switch + * 3. start <- timer value before or after jiffy switch + * 4. post_start <- When we are sure that jiffy switch has happened + * + * Note, we don't know anything about order of 2 and 3. + * Now, by looking at post_start and pre_start difference, we can + * check whether any asynchronous event happened or not + */ + + for (i = 0; i < MAX_DIRECT_CALIBRATION_RETRIES; i++) { + pre_start = 0; + read_current_timer(&start); + start_jiffies = jiffies; + while (jiffies <= (start_jiffies + 1)) { + pre_start = start; + read_current_timer(&start); + } + read_current_timer(&post_start); + + pre_end = 0; + end = post_start; + while (jiffies <= + (start_jiffies + 1 + DELAY_CALIBRATION_TICKS)) { + pre_end = end; + read_current_timer(&end); + } + read_current_timer(&post_end); + + tsc_rate_max = (post_end - pre_start) / DELAY_CALIBRATION_TICKS; + tsc_rate_min = (pre_end - post_start) / DELAY_CALIBRATION_TICKS; + + /* + * If the upper limit and lower limit of the tsc_rate is + * >= 12.5% apart, redo calibration. + */ + if (pre_start != 0 && pre_end != 0 && + (tsc_rate_max - tsc_rate_min) < (tsc_rate_max >> 3)) { + good_tsc_count++; + good_tsc_sum += tsc_rate_max; + } + } + + if (good_tsc_count) + return (good_tsc_sum/good_tsc_count); + + printk(KERN_WARNING "calibrate_delay_direct() failed to get a good " + "estimate for loops_per_jiffy.\nProbably due to long platform interrupts. Consider using \"lpj=\" boot option.\n"); + return 0; +} +#else +static unsigned long __devinit calibrate_delay_direct(void) {return 0;} +#endif + /* * This is the number of bits of precision for the loops_per_jiffy. Each * bit takes on average 1.5/HZ seconds. This (like the original) is a little @@ -35,6 +123,12 @@ void __devinit calibrate_delay(void) "%lu.%02lu BogoMIPS preset\n", loops_per_jiffy/(500000/HZ), (loops_per_jiffy/(5000/HZ)) % 100); + } else if ((loops_per_jiffy = calibrate_delay_direct()) != 0) { + printk("Calibrating delay using timer specific routine.. "); + printk("%lu.%02lu BogoMIPS (lpj=%lu)\n", + loops_per_jiffy/(500000/HZ), + (loops_per_jiffy/(5000/HZ)) % 100, + loops_per_jiffy); } else { loops_per_jiffy = (1<<12); |
