+++ /dev/null
-/*
- * 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;
- unsigned long rate;
- u32 mult;
- u32 shift;
- bool suspended;
-};
-
-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 notrace cyc_to_ns(u64 cyc, u32 mult, u32 shift)
-{
- return (cyc * mult) >> shift;
-}
-
-static unsigned long long notrace cyc_to_sched_clock(u32 cyc, u32 mask)
-{
- u64 epoch_ns;
- u32 epoch_cyc;
-
- /*
- * 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;
-
- if (cd.rate > rate)
- return;
-
- BUG_ON(bits > 32);
- WARN_ON(!irqs_disabled());
- read_sched_clock = read;
- sched_clock_mask = (1 << bits) - 1;
- cd.rate = rate;
-
- /* 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);
-}
-
-static unsigned long long notrace sched_clock_32(void)
-{
- u32 cyc = read_sched_clock();
- return cyc_to_sched_clock(cyc, sched_clock_mask);
-}
-
-unsigned long long __read_mostly (*sched_clock_func)(void) = sched_clock_32;
-
-unsigned long long notrace sched_clock(void)
-{
- if (cd.suspended)
- return cd.epoch_ns;
-
- return sched_clock_func();
-}
-
-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);
projects / karo-tx-linux.git / blobdiff