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>

diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 20660dd..6c273cd 100644 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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;
 }