207 lines
4.8 KiB
C
207 lines
4.8 KiB
C
/*
|
|
* sched_clock.c: support for extending counters to full 64-bit ns counter
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License version 2 as
|
|
* published by the Free Software Foundation.
|
|
*/
|
|
#include <linux/clocksource.h>
|
|
#include <linux/init.h>
|
|
#include <linux/jiffies.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/moduleparam.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/syscore_ops.h>
|
|
#include <linux/timer.h>
|
|
|
|
#include <asm/sched_clock.h>
|
|
|
|
struct clock_data {
|
|
u64 epoch_ns;
|
|
u32 epoch_cyc;
|
|
u32 epoch_cyc_copy;
|
|
u32 mult;
|
|
u32 shift;
|
|
bool suspended;
|
|
bool needs_suspend;
|
|
};
|
|
|
|
static void sched_clock_poll(unsigned long wrap_ticks);
|
|
static DEFINE_TIMER(sched_clock_timer, sched_clock_poll, 0, 0);
|
|
static int irqtime = -1;
|
|
|
|
core_param(irqtime, irqtime, int, 0400);
|
|
|
|
static struct clock_data cd = {
|
|
.mult = NSEC_PER_SEC / HZ,
|
|
};
|
|
|
|
static u32 __read_mostly sched_clock_mask = 0xffffffff;
|
|
|
|
static u32 notrace jiffy_sched_clock_read(void)
|
|
{
|
|
return (u32)(jiffies - INITIAL_JIFFIES);
|
|
}
|
|
|
|
static u32 __read_mostly (*read_sched_clock)(void) = jiffy_sched_clock_read;
|
|
|
|
static inline u64 cyc_to_ns(u64 cyc, u32 mult, u32 shift)
|
|
{
|
|
return (cyc * mult) >> shift;
|
|
}
|
|
|
|
static unsigned long long cyc_to_sched_clock(u32 cyc, u32 mask)
|
|
{
|
|
u64 epoch_ns;
|
|
u32 epoch_cyc;
|
|
|
|
if (cd.suspended)
|
|
return cd.epoch_ns;
|
|
|
|
/*
|
|
* Load the epoch_cyc and epoch_ns atomically. We do this by
|
|
* ensuring that we always write epoch_cyc, epoch_ns and
|
|
* epoch_cyc_copy in strict order, and read them in strict order.
|
|
* If epoch_cyc and epoch_cyc_copy are not equal, then we're in
|
|
* the middle of an update, and we should repeat the load.
|
|
*/
|
|
do {
|
|
epoch_cyc = cd.epoch_cyc;
|
|
smp_rmb();
|
|
epoch_ns = cd.epoch_ns;
|
|
smp_rmb();
|
|
} while (epoch_cyc != cd.epoch_cyc_copy);
|
|
|
|
return epoch_ns + cyc_to_ns((cyc - epoch_cyc) & mask, cd.mult, cd.shift);
|
|
}
|
|
|
|
/*
|
|
* Atomically update the sched_clock epoch.
|
|
*/
|
|
static void notrace update_sched_clock(void)
|
|
{
|
|
unsigned long flags;
|
|
u32 cyc;
|
|
u64 ns;
|
|
|
|
cyc = read_sched_clock();
|
|
ns = cd.epoch_ns +
|
|
cyc_to_ns((cyc - cd.epoch_cyc) & sched_clock_mask,
|
|
cd.mult, cd.shift);
|
|
/*
|
|
* Write epoch_cyc and epoch_ns in a way that the update is
|
|
* detectable in cyc_to_fixed_sched_clock().
|
|
*/
|
|
raw_local_irq_save(flags);
|
|
cd.epoch_cyc_copy = cyc;
|
|
smp_wmb();
|
|
cd.epoch_ns = ns;
|
|
smp_wmb();
|
|
cd.epoch_cyc = cyc;
|
|
raw_local_irq_restore(flags);
|
|
}
|
|
|
|
static void sched_clock_poll(unsigned long wrap_ticks)
|
|
{
|
|
mod_timer(&sched_clock_timer, round_jiffies(jiffies + wrap_ticks));
|
|
update_sched_clock();
|
|
}
|
|
|
|
void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate)
|
|
{
|
|
unsigned long r, w;
|
|
u64 res, wrap;
|
|
char r_unit;
|
|
|
|
BUG_ON(bits > 32);
|
|
WARN_ON(!irqs_disabled());
|
|
WARN_ON(read_sched_clock != jiffy_sched_clock_read);
|
|
read_sched_clock = read;
|
|
sched_clock_mask = (1 << bits) - 1;
|
|
|
|
/* calculate the mult/shift to convert counter ticks to ns. */
|
|
clocks_calc_mult_shift(&cd.mult, &cd.shift, rate, NSEC_PER_SEC, 0);
|
|
|
|
r = rate;
|
|
if (r >= 4000000) {
|
|
r /= 1000000;
|
|
r_unit = 'M';
|
|
} else if (r >= 1000) {
|
|
r /= 1000;
|
|
r_unit = 'k';
|
|
} else
|
|
r_unit = ' ';
|
|
|
|
/* calculate how many ns until we wrap */
|
|
wrap = cyc_to_ns((1ULL << bits) - 1, cd.mult, cd.shift);
|
|
do_div(wrap, NSEC_PER_MSEC);
|
|
w = wrap;
|
|
|
|
/* calculate the ns resolution of this counter */
|
|
res = cyc_to_ns(1ULL, cd.mult, cd.shift);
|
|
pr_info("sched_clock: %u bits at %lu%cHz, resolution %lluns, wraps every %lums\n",
|
|
bits, r, r_unit, res, w);
|
|
|
|
/*
|
|
* Start the timer to keep sched_clock() properly updated and
|
|
* sets the initial epoch.
|
|
*/
|
|
sched_clock_timer.data = msecs_to_jiffies(w - (w / 10));
|
|
update_sched_clock();
|
|
|
|
/*
|
|
* Ensure that sched_clock() starts off at 0ns
|
|
*/
|
|
cd.epoch_ns = 0;
|
|
|
|
/* Enable IRQ time accounting if we have a fast enough sched_clock */
|
|
if (irqtime > 0 || (irqtime == -1 && rate >= 1000000))
|
|
enable_sched_clock_irqtime();
|
|
|
|
pr_debug("Registered %pF as sched_clock source\n", read);
|
|
}
|
|
|
|
unsigned long long notrace sched_clock(void)
|
|
{
|
|
u32 cyc = read_sched_clock();
|
|
return cyc_to_sched_clock(cyc, sched_clock_mask);
|
|
}
|
|
|
|
void __init sched_clock_postinit(void)
|
|
{
|
|
/*
|
|
* If no sched_clock function has been provided at that point,
|
|
* make it the final one one.
|
|
*/
|
|
if (read_sched_clock == jiffy_sched_clock_read)
|
|
setup_sched_clock(jiffy_sched_clock_read, 32, HZ);
|
|
|
|
sched_clock_poll(sched_clock_timer.data);
|
|
}
|
|
|
|
static int sched_clock_suspend(void)
|
|
{
|
|
sched_clock_poll(sched_clock_timer.data);
|
|
cd.suspended = true;
|
|
return 0;
|
|
}
|
|
|
|
static void sched_clock_resume(void)
|
|
{
|
|
cd.epoch_cyc = read_sched_clock();
|
|
cd.epoch_cyc_copy = cd.epoch_cyc;
|
|
cd.suspended = false;
|
|
}
|
|
|
|
static struct syscore_ops sched_clock_ops = {
|
|
.suspend = sched_clock_suspend,
|
|
.resume = sched_clock_resume,
|
|
};
|
|
|
|
static int __init sched_clock_syscore_init(void)
|
|
{
|
|
register_syscore_ops(&sched_clock_ops);
|
|
return 0;
|
|
}
|
|
device_initcall(sched_clock_syscore_init);
|