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Commit 0fa88cb4 authored by Xunlei Pang's avatar Xunlei Pang Committed by Ingo Molnar
Browse files

time, drivers/rtc: Don't bother with rtc_resume() for the nonstop clocksource 



If a system does not provide a persistent_clock(), the time
will be updated on resume by rtc_resume(). With the addition
of the non-stop clocksources for suspend timing, those systems
set the time on resume in timekeeping_resume(), but may not
provide a valid persistent_clock().

This results in the rtc_resume() logic thinking no one has set
the time and it then will over-write the suspend time again,
which is not necessary and only increases clock error.

So, fix this for rtc_resume().

This patch also improves the name of persistent_clock_exist to
make it more grammatical.

Signed-off-by: default avatarXunlei Pang <pang.xunlei@linaro.org>
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1427945681-29972-19-git-send-email-john.stultz@linaro.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 264bb3f7

drivers/rtc/class.c

+2 −2
Original line number Diff line number Diff line
@@ -55,7 +55,7 @@ static int rtc_suspend(struct device *dev) 
	struct timespec64	delta, delta_delta;

	int err;



	if (has_persistent_clock())

	if (timekeeping_rtc_skipsuspend())

		return 0;



	if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
@@ -102,7 +102,7 @@ static int rtc_resume(struct device *dev) 
	struct timespec64	sleep_time;

	int err;



	if (has_persistent_clock())

	if (timekeeping_rtc_skipresume())

		return 0;



	rtc_hctosys_ret = -ENODEV;

include/linux/timekeeping.h

+3 −6
Original line number Diff line number Diff line
@@ -248,6 +248,9 @@ static inline void timekeeping_clocktai(struct timespec *ts) 
/*

 * RTC specific

 */

extern bool timekeeping_rtc_skipsuspend(void);

extern bool timekeeping_rtc_skipresume(void);



extern void timekeeping_inject_sleeptime64(struct timespec64 *delta);



/*
@@ -259,14 +262,8 @@ extern void getnstime_raw_and_real(struct timespec *ts_raw, 
/*

 * Persistent clock related interfaces

 */

extern bool persistent_clock_exist;

extern int persistent_clock_is_local;



static inline bool has_persistent_clock(void)

{

	return persistent_clock_exist;

}



extern void read_persistent_clock(struct timespec *ts);

extern void read_persistent_clock64(struct timespec64 *ts);

extern void read_boot_clock(struct timespec *ts);

kernel/time/timekeeping.c

+49 −17
Original line number Diff line number Diff line
@@ -64,9 +64,6 @@ static struct tk_fast tk_fast_raw ____cacheline_aligned; 
/* flag for if timekeeping is suspended */

int __read_mostly timekeeping_suspended;



/* Flag for if there is a persistent clock on this platform */

bool __read_mostly persistent_clock_exist = false;



static inline void tk_normalize_xtime(struct timekeeper *tk)

{

	while (tk->tkr_mono.xtime_nsec >= ((u64)NSEC_PER_SEC << tk->tkr_mono.shift)) {
@@ -1204,6 +1201,12 @@ void __weak read_boot_clock64(struct timespec64 *ts64) 
	*ts64 = timespec_to_timespec64(ts);

}



/* Flag for if timekeeping_resume() has injected sleeptime */

static bool sleeptime_injected;



/* Flag for if there is a persistent clock on this platform */

static bool persistent_clock_exists;



/*

 * timekeeping_init - Initializes the clocksource and common timekeeping values

 */
@@ -1221,7 +1224,7 @@ void __init timekeeping_init(void) 
		now.tv_sec = 0;

		now.tv_nsec = 0;

	} else if (now.tv_sec || now.tv_nsec)

		persistent_clock_exist = true;

		persistent_clock_exists = true;



	read_boot_clock64(&boot);

	if (!timespec64_valid_strict(&boot)) {
@@ -1281,12 +1284,48 @@ static void __timekeeping_inject_sleeptime(struct timekeeper *tk, 
}



#if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)

/**

 * We have three kinds of time sources to use for sleep time

 * injection, the preference order is:

 * 1) non-stop clocksource

 * 2) persistent clock (ie: RTC accessible when irqs are off)

 * 3) RTC

 *

 * 1) and 2) are used by timekeeping, 3) by RTC subsystem.

 * If system has neither 1) nor 2), 3) will be used finally.

 *

 *

 * If timekeeping has injected sleeptime via either 1) or 2),

 * 3) becomes needless, so in this case we don't need to call

 * rtc_resume(), and this is what timekeeping_rtc_skipresume()

 * means.

 */

bool timekeeping_rtc_skipresume(void)

{

	return sleeptime_injected;

}



/**

 * 1) can be determined whether to use or not only when doing

 * timekeeping_resume() which is invoked after rtc_suspend(),

 * so we can't skip rtc_suspend() surely if system has 1).

 *

 * But if system has 2), 2) will definitely be used, so in this

 * case we don't need to call rtc_suspend(), and this is what

 * timekeeping_rtc_skipsuspend() means.

 */

bool timekeeping_rtc_skipsuspend(void)

{

	return persistent_clock_exists;

}



/**

 * timekeeping_inject_sleeptime64 - Adds suspend interval to timeekeeping values

 * @delta: pointer to a timespec64 delta value

 *

 * This hook is for architectures that cannot support read_persistent_clock64

 * because their RTC/persistent clock is only accessible when irqs are enabled.

 * and also don't have an effective nonstop clocksource.

 *

 * This function should only be called by rtc_resume(), and allows

 * a suspend offset to be injected into the timekeeping values.
@@ -1296,13 +1335,6 @@ void timekeeping_inject_sleeptime64(struct timespec64 *delta) 
	struct timekeeper *tk = &tk_core.timekeeper;

	unsigned long flags;



	/*

	 * Make sure we don't set the clock twice, as timekeeping_resume()

	 * already did it

	 */

	if (has_persistent_clock())

		return;



	raw_spin_lock_irqsave(&timekeeper_lock, flags);

	write_seqcount_begin(&tk_core.seq);
@@ -1334,8 +1366,8 @@ void timekeeping_resume(void) 
	unsigned long flags;

	struct timespec64 ts_new, ts_delta;

	cycle_t cycle_now, cycle_delta;

	bool suspendtime_found = false;



	sleeptime_injected = false;

	read_persistent_clock64(&ts_new);



	clockevents_resume();
@@ -1381,13 +1413,13 @@ void timekeeping_resume(void) 
		nsec += ((u64) cycle_delta * mult) >> shift;



		ts_delta = ns_to_timespec64(nsec);

		suspendtime_found = true;

		sleeptime_injected = true;

	} else if (timespec64_compare(&ts_new, &timekeeping_suspend_time) > 0) {

		ts_delta = timespec64_sub(ts_new, timekeeping_suspend_time);

		suspendtime_found = true;

		sleeptime_injected = true;

	}



	if (suspendtime_found)

	if (sleeptime_injected)

		__timekeeping_inject_sleeptime(tk, &ts_delta);



	/* Re-base the last cycle value */
@@ -1421,14 +1453,14 @@ int timekeeping_suspend(void) 
	 * value returned, update the persistent_clock_exists flag.

	 */

	if (timekeeping_suspend_time.tv_sec || timekeeping_suspend_time.tv_nsec)

		persistent_clock_exist = true;

		persistent_clock_exists = true;



	raw_spin_lock_irqsave(&timekeeper_lock, flags);

	write_seqcount_begin(&tk_core.seq);

	timekeeping_forward_now(tk);

	timekeeping_suspended = 1;



	if (has_persistent_clock()) {

	if (persistent_clock_exists) {

		/*

		 * To avoid drift caused by repeated suspend/resumes,

		 * which each can add ~1 second drift error,