diff options
Diffstat (limited to 'arch/i386/kernel/tsc.c')
| -rw-r--r-- | arch/i386/kernel/tsc.c | 161 |
1 files changed, 161 insertions, 0 deletions
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c index 96b307495e5f..7713f86389af 100644 --- a/arch/i386/kernel/tsc.c +++ b/arch/i386/kernel/tsc.c @@ -4,11 +4,14 @@ * See comments there for proper credits. */ +#include <linux/clocksource.h> #include <linux/workqueue.h> #include <linux/cpufreq.h> #include <linux/jiffies.h> #include <linux/init.h> +#include <linux/dmi.h> +#include <asm/delay.h> #include <asm/tsc.h> #include <asm/delay.h> #include <asm/io.h> @@ -315,3 +318,161 @@ static int __init cpufreq_tsc(void) core_initcall(cpufreq_tsc); #endif + +/* clock source code */ + +static unsigned long current_tsc_khz = 0; +static int tsc_update_callback(void); + +static cycle_t read_tsc(void) +{ + cycle_t ret; + + rdtscll(ret); + + return ret; +} + +static struct clocksource clocksource_tsc = { + .name = "tsc", + .rating = 300, + .read = read_tsc, + .mask = (cycle_t)-1, + .mult = 0, /* to be set */ + .shift = 22, + .update_callback = tsc_update_callback, + .is_continuous = 1, +}; + +static int tsc_update_callback(void) +{ + int change = 0; + + /* check to see if we should switch to the safe clocksource: */ + if (clocksource_tsc.rating != 50 && check_tsc_unstable()) { + clocksource_tsc.rating = 50; + reselect_clocksource(); + change = 1; + } + + /* only update if tsc_khz has changed: */ + if (current_tsc_khz != tsc_khz) { + current_tsc_khz = tsc_khz; + clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz, + clocksource_tsc.shift); + change = 1; + } + + return change; +} + +static int __init dmi_mark_tsc_unstable(struct dmi_system_id *d) +{ + printk(KERN_NOTICE "%s detected: marking TSC unstable.\n", + d->ident); + mark_tsc_unstable(); + return 0; +} + +/* List of systems that have known TSC problems */ +static struct dmi_system_id __initdata bad_tsc_dmi_table[] = { + { + .callback = dmi_mark_tsc_unstable, + .ident = "IBM Thinkpad 380XD", + .matches = { + DMI_MATCH(DMI_BOARD_VENDOR, "IBM"), + DMI_MATCH(DMI_BOARD_NAME, "2635FA0"), + }, + }, + {} +}; + +#define TSC_FREQ_CHECK_INTERVAL (10*MSEC_PER_SEC) /* 10sec in MS */ +static struct timer_list verify_tsc_freq_timer; + +/* XXX - Probably should add locking */ +static void verify_tsc_freq(unsigned long unused) +{ + static u64 last_tsc; + static unsigned long last_jiffies; + + u64 now_tsc, interval_tsc; + unsigned long now_jiffies, interval_jiffies; + + + if (check_tsc_unstable()) + return; + + rdtscll(now_tsc); + now_jiffies = jiffies; + + if (!last_jiffies) { + goto out; + } + + interval_jiffies = now_jiffies - last_jiffies; + interval_tsc = now_tsc - last_tsc; + interval_tsc *= HZ; + do_div(interval_tsc, cpu_khz*1000); + + if (interval_tsc < (interval_jiffies * 3 / 4)) { + printk("TSC appears to be running slowly. " + "Marking it as unstable\n"); + mark_tsc_unstable(); + return; + } + +out: + last_tsc = now_tsc; + last_jiffies = now_jiffies; + /* set us up to go off on the next interval: */ + mod_timer(&verify_tsc_freq_timer, + jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL)); +} + +/* + * Make an educated guess if the TSC is trustworthy and synchronized + * over all CPUs. + */ +static __init int unsynchronized_tsc(void) +{ + /* + * Intel systems are normally all synchronized. + * Exceptions must mark TSC as unstable: + */ + if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) + return 0; + + /* assume multi socket systems are not synchronized: */ + return num_possible_cpus() > 1; +} + +static int __init init_tsc_clocksource(void) +{ + + if (cpu_has_tsc && tsc_khz && !tsc_disable) { + /* check blacklist */ + dmi_check_system(bad_tsc_dmi_table); + + if (unsynchronized_tsc()) /* mark unstable if unsynced */ + mark_tsc_unstable(); + current_tsc_khz = tsc_khz; + clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz, + clocksource_tsc.shift); + /* lower the rating if we already know its unstable: */ + if (check_tsc_unstable()) + clocksource_tsc.rating = 50; + + init_timer(&verify_tsc_freq_timer); + verify_tsc_freq_timer.function = verify_tsc_freq; + verify_tsc_freq_timer.expires = + jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL); + add_timer(&verify_tsc_freq_timer); + + return register_clocksource(&clocksource_tsc); + } + + return 0; +} + +module_init(init_tsc_clocksource); |