07190a08ee
The Geode can safely use the TSC for highres, since: 1) Does not support frequency scaling, 2) The TSC _does_ count when the CPU is halted. Furthermore, the Geode supports a mode called "suspension on halt", where Suspend mode (which interacts with the power management states) is entered. TSC counting during suspend mode is controlled by bit 8 of the Bus Controller Configuration Register #0 (thanks Tom!). 3) no SMP :) Check if "RTSC counts during suspension" and remove the requirement for verification, so the clocksource code can safely select it as an timesource for the highres timers subsystem. Signed-off-by: Marcelo Tosatti <marcelo@kvack.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: john stultz <johnstul@us.ibm.com> Cc: Roman Zippel <zippel@linux-m68k.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
410 lines
8.9 KiB
C
410 lines
8.9 KiB
C
/*
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* This code largely moved from arch/i386/kernel/timer/timer_tsc.c
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* which was originally moved from arch/i386/kernel/time.c.
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* See comments there for proper credits.
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*/
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#include <linux/clocksource.h>
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#include <linux/workqueue.h>
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#include <linux/cpufreq.h>
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#include <linux/jiffies.h>
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#include <linux/init.h>
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#include <linux/dmi.h>
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#include <asm/delay.h>
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#include <asm/tsc.h>
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#include <asm/io.h>
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#include "mach_timer.h"
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/*
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* On some systems the TSC frequency does not
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* change with the cpu frequency. So we need
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* an extra value to store the TSC freq
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*/
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unsigned int tsc_khz;
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unsigned long long (*custom_sched_clock)(void);
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int tsc_disable;
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#ifdef CONFIG_X86_TSC
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static int __init tsc_setup(char *str)
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{
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printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
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"cannot disable TSC.\n");
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return 1;
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}
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#else
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/*
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* disable flag for tsc. Takes effect by clearing the TSC cpu flag
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* in cpu/common.c
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*/
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static int __init tsc_setup(char *str)
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{
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tsc_disable = 1;
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return 1;
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}
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#endif
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__setup("notsc", tsc_setup);
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/*
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* code to mark and check if the TSC is unstable
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* due to cpufreq or due to unsynced TSCs
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*/
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static int tsc_unstable;
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static inline int check_tsc_unstable(void)
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{
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return tsc_unstable;
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}
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/* Accellerators for sched_clock()
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* convert from cycles(64bits) => nanoseconds (64bits)
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* basic equation:
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* ns = cycles / (freq / ns_per_sec)
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* ns = cycles * (ns_per_sec / freq)
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* ns = cycles * (10^9 / (cpu_khz * 10^3))
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* ns = cycles * (10^6 / cpu_khz)
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*
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* Then we use scaling math (suggested by george@mvista.com) to get:
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* ns = cycles * (10^6 * SC / cpu_khz) / SC
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* ns = cycles * cyc2ns_scale / SC
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*
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* And since SC is a constant power of two, we can convert the div
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* into a shift.
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*
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* We can use khz divisor instead of mhz to keep a better percision, since
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* cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
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* (mathieu.desnoyers@polymtl.ca)
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*
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* -johnstul@us.ibm.com "math is hard, lets go shopping!"
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*/
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static unsigned long cyc2ns_scale __read_mostly;
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#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
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static inline void set_cyc2ns_scale(unsigned long cpu_khz)
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{
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cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz;
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}
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static inline unsigned long long cycles_2_ns(unsigned long long cyc)
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{
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return (cyc * cyc2ns_scale) >> CYC2NS_SCALE_FACTOR;
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}
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/*
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* Scheduler clock - returns current time in nanosec units.
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*/
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unsigned long long sched_clock(void)
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{
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unsigned long long this_offset;
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if (unlikely(custom_sched_clock))
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return (*custom_sched_clock)();
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/*
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* Fall back to jiffies if there's no TSC available:
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*/
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if (unlikely(tsc_disable))
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/* No locking but a rare wrong value is not a big deal: */
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return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
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/* read the Time Stamp Counter: */
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rdtscll(this_offset);
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/* return the value in ns */
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return cycles_2_ns(this_offset);
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}
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static unsigned long calculate_cpu_khz(void)
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{
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unsigned long long start, end;
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unsigned long count;
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u64 delta64;
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int i;
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unsigned long flags;
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local_irq_save(flags);
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/* run 3 times to ensure the cache is warm */
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for (i = 0; i < 3; i++) {
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mach_prepare_counter();
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rdtscll(start);
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mach_countup(&count);
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rdtscll(end);
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}
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/*
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* Error: ECTCNEVERSET
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* The CTC wasn't reliable: we got a hit on the very first read,
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* or the CPU was so fast/slow that the quotient wouldn't fit in
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* 32 bits..
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*/
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if (count <= 1)
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goto err;
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delta64 = end - start;
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/* cpu freq too fast: */
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if (delta64 > (1ULL<<32))
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goto err;
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/* cpu freq too slow: */
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if (delta64 <= CALIBRATE_TIME_MSEC)
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goto err;
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delta64 += CALIBRATE_TIME_MSEC/2; /* round for do_div */
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do_div(delta64,CALIBRATE_TIME_MSEC);
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local_irq_restore(flags);
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return (unsigned long)delta64;
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err:
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local_irq_restore(flags);
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return 0;
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}
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int recalibrate_cpu_khz(void)
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{
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#ifndef CONFIG_SMP
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unsigned long cpu_khz_old = cpu_khz;
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if (cpu_has_tsc) {
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cpu_khz = calculate_cpu_khz();
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tsc_khz = cpu_khz;
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cpu_data[0].loops_per_jiffy =
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cpufreq_scale(cpu_data[0].loops_per_jiffy,
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cpu_khz_old, cpu_khz);
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return 0;
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} else
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return -ENODEV;
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#else
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return -ENODEV;
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#endif
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}
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EXPORT_SYMBOL(recalibrate_cpu_khz);
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void __init tsc_init(void)
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{
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if (!cpu_has_tsc || tsc_disable)
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goto out_no_tsc;
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cpu_khz = calculate_cpu_khz();
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tsc_khz = cpu_khz;
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if (!cpu_khz)
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goto out_no_tsc;
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printk("Detected %lu.%03lu MHz processor.\n",
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(unsigned long)cpu_khz / 1000,
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(unsigned long)cpu_khz % 1000);
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set_cyc2ns_scale(cpu_khz);
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use_tsc_delay();
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return;
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out_no_tsc:
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/*
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* Set the tsc_disable flag if there's no TSC support, this
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* makes it a fast flag for the kernel to see whether it
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* should be using the TSC.
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*/
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tsc_disable = 1;
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}
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#ifdef CONFIG_CPU_FREQ
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/*
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* if the CPU frequency is scaled, TSC-based delays will need a different
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* loops_per_jiffy value to function properly.
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*/
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static unsigned int ref_freq = 0;
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static unsigned long loops_per_jiffy_ref = 0;
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static unsigned long cpu_khz_ref = 0;
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static int
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time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, void *data)
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{
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struct cpufreq_freqs *freq = data;
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if (val != CPUFREQ_RESUMECHANGE && val != CPUFREQ_SUSPENDCHANGE)
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write_seqlock_irq(&xtime_lock);
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if (!ref_freq) {
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if (!freq->old){
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ref_freq = freq->new;
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goto end;
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}
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ref_freq = freq->old;
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loops_per_jiffy_ref = cpu_data[freq->cpu].loops_per_jiffy;
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cpu_khz_ref = cpu_khz;
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}
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if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) ||
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(val == CPUFREQ_POSTCHANGE && freq->old > freq->new) ||
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(val == CPUFREQ_RESUMECHANGE)) {
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if (!(freq->flags & CPUFREQ_CONST_LOOPS))
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cpu_data[freq->cpu].loops_per_jiffy =
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cpufreq_scale(loops_per_jiffy_ref,
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ref_freq, freq->new);
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if (cpu_khz) {
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if (num_online_cpus() == 1)
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cpu_khz = cpufreq_scale(cpu_khz_ref,
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ref_freq, freq->new);
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if (!(freq->flags & CPUFREQ_CONST_LOOPS)) {
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tsc_khz = cpu_khz;
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set_cyc2ns_scale(cpu_khz);
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/*
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* TSC based sched_clock turns
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* to junk w/ cpufreq
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*/
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mark_tsc_unstable();
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}
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}
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}
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end:
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if (val != CPUFREQ_RESUMECHANGE && val != CPUFREQ_SUSPENDCHANGE)
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write_sequnlock_irq(&xtime_lock);
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return 0;
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}
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static struct notifier_block time_cpufreq_notifier_block = {
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.notifier_call = time_cpufreq_notifier
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};
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static int __init cpufreq_tsc(void)
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{
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return cpufreq_register_notifier(&time_cpufreq_notifier_block,
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CPUFREQ_TRANSITION_NOTIFIER);
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}
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core_initcall(cpufreq_tsc);
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#endif
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/* clock source code */
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static unsigned long current_tsc_khz = 0;
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static cycle_t read_tsc(void)
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{
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cycle_t ret;
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rdtscll(ret);
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return ret;
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}
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static struct clocksource clocksource_tsc = {
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.name = "tsc",
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.rating = 300,
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.read = read_tsc,
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.mask = CLOCKSOURCE_MASK(64),
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.mult = 0, /* to be set */
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.shift = 22,
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.flags = CLOCK_SOURCE_IS_CONTINUOUS |
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CLOCK_SOURCE_MUST_VERIFY,
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};
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void mark_tsc_unstable(void)
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{
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if (!tsc_unstable) {
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tsc_unstable = 1;
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/* Can be called before registration */
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if (clocksource_tsc.mult)
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clocksource_change_rating(&clocksource_tsc, 0);
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else
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clocksource_tsc.rating = 0;
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}
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}
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EXPORT_SYMBOL_GPL(mark_tsc_unstable);
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static int __init dmi_mark_tsc_unstable(struct dmi_system_id *d)
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{
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printk(KERN_NOTICE "%s detected: marking TSC unstable.\n",
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d->ident);
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tsc_unstable = 1;
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return 0;
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}
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/* List of systems that have known TSC problems */
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static struct dmi_system_id __initdata bad_tsc_dmi_table[] = {
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{
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.callback = dmi_mark_tsc_unstable,
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.ident = "IBM Thinkpad 380XD",
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.matches = {
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DMI_MATCH(DMI_BOARD_VENDOR, "IBM"),
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DMI_MATCH(DMI_BOARD_NAME, "2635FA0"),
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},
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},
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{}
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};
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/*
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* Make an educated guess if the TSC is trustworthy and synchronized
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* over all CPUs.
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*/
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__cpuinit int unsynchronized_tsc(void)
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{
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if (!cpu_has_tsc || tsc_unstable)
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return 1;
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/*
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* Intel systems are normally all synchronized.
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* Exceptions must mark TSC as unstable:
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*/
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if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
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/* assume multi socket systems are not synchronized: */
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if (num_possible_cpus() > 1)
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tsc_unstable = 1;
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}
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return tsc_unstable;
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}
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/*
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* Geode_LX - the OLPC CPU has a possibly a very reliable TSC
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*/
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#ifdef CONFIG_MGEODE_LX
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/* RTSC counts during suspend */
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#define RTSC_SUSP 0x100
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static void __init check_geode_tsc_reliable(void)
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{
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unsigned long val;
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rdmsrl(MSR_GEODE_BUSCONT_CONF0, val);
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if ((val & RTSC_SUSP))
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clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
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}
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#else
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static inline void check_geode_tsc_reliable(void) { }
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#endif
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static int __init init_tsc_clocksource(void)
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{
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if (cpu_has_tsc && tsc_khz && !tsc_disable) {
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/* check blacklist */
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dmi_check_system(bad_tsc_dmi_table);
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unsynchronized_tsc();
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check_geode_tsc_reliable();
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current_tsc_khz = tsc_khz;
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clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
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clocksource_tsc.shift);
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/* lower the rating if we already know its unstable: */
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if (check_tsc_unstable()) {
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clocksource_tsc.rating = 0;
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clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
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}
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return clocksource_register(&clocksource_tsc);
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}
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return 0;
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}
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module_init(init_tsc_clocksource);
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