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Commit 31ade306 authored by Feng Tang's avatar Feng Tang Committed by John Stultz
Browse files

timekeeping: Add persistent_clock_exist flag 



In current kernel, there are several places which need to check
whether there is a persistent clock for the platform. Current check
is done by calling the read_persistent_clock() and validating its
return value.

So one optimization is to do the check only once in timekeeping_init(),
and use a flag persistent_clock_exist to record it.

v2: Add a has_persistent_clock() helper function, as suggested by John.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Signed-off-by: default avatarFeng Tang <feng.tang@intel.com>
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
parent f0dbe81f

include/linux/time.h

+6 −0
Original line number Diff line number Diff line
@@ -115,6 +115,12 @@ static inline bool timespec_valid_strict(const struct timespec *ts) 
	return true;

}



extern bool persistent_clock_exist;

static inline bool has_persistent_clock(void)

{

	return persistent_clock_exist;

}



extern void read_persistent_clock(struct timespec *ts);

extern void read_boot_clock(struct timespec *ts);

extern int update_persistent_clock(struct timespec now);

kernel/time/timekeeping.c

+11 −5
Original line number Diff line number Diff line
@@ -28,6 +28,9 @@ static struct timekeeper timekeeper; 
/* 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->xtime_nsec >= ((u64)NSEC_PER_SEC << tk->shift)) {
@@ -609,12 +612,14 @@ void __init timekeeping_init(void) 
	struct timespec now, boot, tmp;



	read_persistent_clock(&now);



	if (!timespec_valid_strict(&now)) {

		pr_warn("WARNING: Persistent clock returned invalid value!\n"

			"         Check your CMOS/BIOS settings.\n");

		now.tv_sec = 0;

		now.tv_nsec = 0;

	}

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

		persistent_clock_exist = true;



	read_boot_clock(&boot);

	if (!timespec_valid_strict(&boot)) {
@@ -687,11 +692,12 @@ void timekeeping_inject_sleeptime(struct timespec *delta) 
{

	struct timekeeper *tk = &timekeeper;

	unsigned long flags;

	struct timespec ts;



	/* Make sure we don't set the clock twice */

	read_persistent_clock(&ts);

	if (!(ts.tv_sec == 0 && ts.tv_nsec == 0))

	/*

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

	 * already did it

	 */

	if (has_persistent_clock())

		return;



	write_seqlock_irqsave(&tk->lock, flags);