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Subject[tip:timers/core] clocksource: Mostly kill clocksource_register()
Commit-ID:  f8935983f110505daa38e8d36ee406807f83a069
Gitweb: http://git.kernel.org/tip/f8935983f110505daa38e8d36ee406807f83a069
Author: John Stultz <john.stultz@linaro.org>
AuthorDate: Wed, 11 Mar 2015 21:16:37 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 13 Mar 2015 08:07:06 +0100

clocksource: Mostly kill clocksource_register()

A long running project has been to clean up remaining uses
of clocksource_register(), replacing it with the simpler
clocksource_register_khz/hz() functions.

However, there are a few cases where we need to self-define
our mult/shift values, so switch the function to a more
obviously internal __clocksource_register() name, and
consolidate much of the internal logic so we don't have
duplication.

Signed-off-by: John Stultz <john.stultz@linaro.org>
Cc: Dave Jones <davej@codemonkey.org.uk>
Cc: David S. Miller <davem@davemloft.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1426133800-29329-10-git-send-email-john.stultz@linaro.org
[ Minor cleanups. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/s390/kernel/time.c | 2 +-
arch/sparc/kernel/time_32.c | 2 +-
include/linux/clocksource.h | 10 +++++-
kernel/time/clocksource.c | 81 +++++++++++++++++++--------------------------
kernel/time/jiffies.c | 4 +--
5 files changed, 47 insertions(+), 52 deletions(-)

diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 20660dd..6c273cd 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -283,7 +283,7 @@ void __init time_init(void)
if (register_external_irq(EXT_IRQ_TIMING_ALERT, timing_alert_interrupt))
panic("Couldn't request external interrupt 0x1406");

- if (clocksource_register(&clocksource_tod) != 0)
+ if (__clocksource_register(&clocksource_tod) != 0)
panic("Could not register TOD clock source");

/* Enable TOD clock interrupts on the boot cpu. */
diff --git a/arch/sparc/kernel/time_32.c b/arch/sparc/kernel/time_32.c
index 2f80d23..a31c0c8 100644
--- a/arch/sparc/kernel/time_32.c
+++ b/arch/sparc/kernel/time_32.c
@@ -191,7 +191,7 @@ static __init int setup_timer_cs(void)
timer_cs.mult = clocksource_hz2mult(sparc_config.clock_rate,
timer_cs.shift);

- return clocksource_register(&timer_cs);
+ return __clocksource_register(&timer_cs);
}

#ifdef CONFIG_SMP
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 16d048c..bd98eaa 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -179,7 +179,6 @@ static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
}


-extern int clocksource_register(struct clocksource*);
extern int clocksource_unregister(struct clocksource*);
extern void clocksource_touch_watchdog(void);
extern struct clocksource* clocksource_get_next(void);
@@ -203,6 +202,15 @@ __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
extern void
__clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq);

+/*
+ * Don't call this unless you are a default clocksource
+ * (AKA: jiffies) and absolutely have to.
+ */
+static inline int __clocksource_register(struct clocksource *cs)
+{
+ return __clocksource_register_scale(cs, 1, 0);
+}
+
static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
{
return __clocksource_register_scale(cs, 1, hz);
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index c4cc04b..5cdf17e 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -656,38 +656,52 @@ static void clocksource_enqueue(struct clocksource *cs)
void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq)
{
u64 sec;
+
/*
- * Calc the maximum number of seconds which we can run before
- * wrapping around. For clocksources which have a mask > 32bit
- * we need to limit the max sleep time to have a good
- * conversion precision. 10 minutes is still a reasonable
- * amount. That results in a shift value of 24 for a
- * clocksource with mask >= 40bit and f >= 4GHz. That maps to
- * ~ 0.06ppm granularity for NTP.
+ * Default clocksources are *special* and self-define their mult/shift.
+ * But, you're not special, so you should specify a freq value.
*/
- sec = cs->mask;
- do_div(sec, freq);
- do_div(sec, scale);
- if (!sec)
- sec = 1;
- else if (sec > 600 && cs->mask > UINT_MAX)
- sec = 600;
-
- clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
- NSEC_PER_SEC / scale, sec * scale);
-
+ if (freq) {
+ /*
+ * Calc the maximum number of seconds which we can run before
+ * wrapping around. For clocksources which have a mask > 32-bit
+ * we need to limit the max sleep time to have a good
+ * conversion precision. 10 minutes is still a reasonable
+ * amount. That results in a shift value of 24 for a
+ * clocksource with mask >= 40-bit and f >= 4GHz. That maps to
+ * ~ 0.06ppm granularity for NTP.
+ */
+ sec = cs->mask;
+ do_div(sec, freq);
+ do_div(sec, scale);
+ if (!sec)
+ sec = 1;
+ else if (sec > 600 && cs->mask > UINT_MAX)
+ sec = 600;
+
+ clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
+ NSEC_PER_SEC / scale, sec * scale);
+ }
/*
* Ensure clocksources that have large 'mult' values don't overflow
* when adjusted.
*/
cs->maxadj = clocksource_max_adjustment(cs);
- while ((cs->mult + cs->maxadj < cs->mult)
- || (cs->mult - cs->maxadj > cs->mult)) {
+ while (freq && ((cs->mult + cs->maxadj < cs->mult)
+ || (cs->mult - cs->maxadj > cs->mult))) {
cs->mult >>= 1;
cs->shift--;
cs->maxadj = clocksource_max_adjustment(cs);
}

+ /*
+ * Only warn for *special* clocksources that self-define
+ * their mult/shift values and don't specify a freq.
+ */
+ WARN_ONCE(cs->mult + cs->maxadj < cs->mult,
+ "timekeeping: Clocksource %s might overflow on 11%% adjustment\n",
+ cs->name);
+
clocksource_update_max_deferment(cs);
}
EXPORT_SYMBOL_GPL(__clocksource_updatefreq_scale);
@@ -719,33 +733,6 @@ int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
}
EXPORT_SYMBOL_GPL(__clocksource_register_scale);

-
-/**
- * clocksource_register - Used to install new clocksources
- * @cs: clocksource to be registered
- *
- * Returns -EBUSY if registration fails, zero otherwise.
- */
-int clocksource_register(struct clocksource *cs)
-{
- /* calculate max adjustment for given mult/shift */
- cs->maxadj = clocksource_max_adjustment(cs);
- WARN_ONCE(cs->mult + cs->maxadj < cs->mult,
- "Clocksource %s might overflow on 11%% adjustment\n",
- cs->name);
-
- /* Update max idle time permitted for this clocksource */
- clocksource_update_max_deferment(cs);
-
- mutex_lock(&clocksource_mutex);
- clocksource_enqueue(cs);
- clocksource_enqueue_watchdog(cs);
- clocksource_select();
- mutex_unlock(&clocksource_mutex);
- return 0;
-}
-EXPORT_SYMBOL(clocksource_register);
-
static void __clocksource_change_rating(struct clocksource *cs, int rating)
{
list_del(&cs->list);
diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c
index 7e41390..c4bb518 100644
--- a/kernel/time/jiffies.c
+++ b/kernel/time/jiffies.c
@@ -95,7 +95,7 @@ EXPORT_SYMBOL(jiffies);

static int __init init_jiffies_clocksource(void)
{
- return clocksource_register(&clocksource_jiffies);
+ return __clocksource_register(&clocksource_jiffies);
}

core_initcall(init_jiffies_clocksource);
@@ -131,6 +131,6 @@ int register_refined_jiffies(long cycles_per_second)

refined_jiffies.mult = ((u32)nsec_per_tick) << JIFFIES_SHIFT;

- clocksource_register(&refined_jiffies);
+ __clocksource_register(&refined_jiffies);
return 0;
}

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