Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / kernel / time / jiffies.c

diff --git a/kernel/kernel/time/jiffies.c b/kernel/kernel/time/jiffies.c
new file mode 100644 (file)
index 0000000..2ede474
--- /dev/null
+++ b/kernel/kernel/time/jiffies.c
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+/***********************************************************************
+* linux/kernel/time/jiffies.c
+*
+* This file contains the jiffies based clocksource.
+*
+* Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com)
+*
+* This program is free software; you can redistribute it and/or modify
+* it under the terms of the GNU General Public License as published by
+* the Free Software Foundation; either version 2 of the License, or
+* (at your option) any later version.
+*
+* This program is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+* GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License
+* along with this program; if not, write to the Free Software
+* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*
+************************************************************************/
+#include <linux/clocksource.h>
+#include <linux/jiffies.h>
+#include <linux/module.h>
+#include <linux/init.h>
+
+#include "timekeeping.h"
+
+/* The Jiffies based clocksource is the lowest common
+ * denominator clock source which should function on
+ * all systems. It has the same coarse resolution as
+ * the timer interrupt frequency HZ and it suffers
+ * inaccuracies caused by missed or lost timer
+ * interrupts and the inability for the timer
+ * interrupt hardware to accuratly tick at the
+ * requested HZ value. It is also not recommended
+ * for "tick-less" systems.
+ */
+#define NSEC_PER_JIFFY ((NSEC_PER_SEC+HZ/2)/HZ)
+
+/* Since jiffies uses a simple NSEC_PER_JIFFY multiplier
+ * conversion, the .shift value could be zero. However
+ * this would make NTP adjustments impossible as they are
+ * in units of 1/2^.shift. Thus we use JIFFIES_SHIFT to
+ * shift both the nominator and denominator the same
+ * amount, and give ntp adjustments in units of 1/2^8
+ *
+ * The value 8 is somewhat carefully chosen, as anything
+ * larger can result in overflows. NSEC_PER_JIFFY grows as
+ * HZ shrinks, so values greater than 8 overflow 32bits when
+ * HZ=100.
+ */
+#if HZ < 34
+#define JIFFIES_SHIFT  6
+#elif HZ < 67
+#define JIFFIES_SHIFT  7
+#else
+#define JIFFIES_SHIFT  8
+#endif
+
+static cycle_t jiffies_read(struct clocksource *cs)
+{
+       return (cycle_t) jiffies;
+}
+
+static struct clocksource clocksource_jiffies = {
+       .name           = "jiffies",
+       .rating         = 1, /* lowest valid rating*/
+       .read           = jiffies_read,
+       .mask           = 0xffffffff, /*32bits*/
+       .mult           = NSEC_PER_JIFFY << JIFFIES_SHIFT, /* details above */
+       .shift          = JIFFIES_SHIFT,
+       .max_cycles     = 10,
+};
+
+__cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(jiffies_lock);
+__cacheline_aligned_in_smp seqcount_t jiffies_seq;
+
+#if (BITS_PER_LONG < 64)
+u64 get_jiffies_64(void)
+{
+       unsigned long seq;
+       u64 ret;
+
+       do {
+               seq = read_seqcount_begin(&jiffies_seq);
+               ret = jiffies_64;
+       } while (read_seqcount_retry(&jiffies_seq, seq));
+       return ret;
+}
+EXPORT_SYMBOL(get_jiffies_64);
+#endif
+
+EXPORT_SYMBOL(jiffies);
+
+static int __init init_jiffies_clocksource(void)
+{
+       return __clocksource_register(&clocksource_jiffies);
+}
+
+core_initcall(init_jiffies_clocksource);
+
+struct clocksource * __init __weak clocksource_default_clock(void)
+{
+       return &clocksource_jiffies;
+}
+
+struct clocksource refined_jiffies;
+
+int register_refined_jiffies(long cycles_per_second)
+{
+       u64 nsec_per_tick, shift_hz;
+       long cycles_per_tick;
+
+
+
+       refined_jiffies = clocksource_jiffies;
+       refined_jiffies.name = "refined-jiffies";
+       refined_jiffies.rating++;
+
+       /* Calc cycles per tick */
+       cycles_per_tick = (cycles_per_second + HZ/2)/HZ;
+       /* shift_hz stores hz<<8 for extra accuracy */
+       shift_hz = (u64)cycles_per_second << 8;
+       shift_hz += cycles_per_tick/2;
+       do_div(shift_hz, cycles_per_tick);
+       /* Calculate nsec_per_tick using shift_hz */
+       nsec_per_tick = (u64)NSEC_PER_SEC << 8;
+       nsec_per_tick += (u32)shift_hz/2;
+       do_div(nsec_per_tick, (u32)shift_hz);
+
+       refined_jiffies.mult = ((u32)nsec_per_tick) << JIFFIES_SHIFT;
+
+       __clocksource_register(&refined_jiffies);
+       return 0;
+}