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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: Xunlei Pang <pang.xunlei@linaro.org>
Signed-off-by: John 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Xunlei Pang 2015-04-01 20:34:38 -07:00 committed by Ingo Molnar
parent 264bb3f79f
commit 0fa88cb4b8
3 changed files with 54 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/rtc/class.c
View File

@ -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;

9
include/linux/timekeeping.h
View File

@ -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);

66
kernel/time/timekeeping.c
View File

@ -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,