sched_clock: Make ARM's sched_clock generic for all architectures
Nothing about the sched_clock implementation in the ARM port is
specific to the architecture. Generalize the code so that other
architectures can use it by selecting GENERIC_SCHED_CLOCK.
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
[jstultz: Merge minor collisions with other patches in my tree]
Signed-off-by: John Stultz <john.stultz@linaro.org>
diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
new file mode 100644
index 0000000..aad1ae6
--- /dev/null
+++ b/kernel/time/sched_clock.c
@@ -0,0 +1,215 @@
+/*
+ * 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 <linux/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);