Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timer updates from Thomas Gleixner:
 "Yet another big pile of changes:

   - More year 2038 work from Arnd slowly reaching the point where we
     need to think about the syscalls themself.

   - A new timer function which allows to conditionally (re)arm a timer
     only when it's either not running or the new expiry time is sooner
     than the armed expiry time. This allows to use a single timer for
     multiple timeout requirements w/o caring about the first expiry
     time at the call site.

   - A new NMI safe accessor to clock real time for the printk timestamp
     work. Can be used by tracing, perf as well if required.

   - A large number of timer setup conversions from Kees which got
     collected here because either maintainers requested so or they
     simply got ignored. As Kees pointed out already there are a few
     trivial merge conflicts and some redundant commits which was
     unavoidable due to the size of this conversion effort.

   - Avoid a redundant iteration in the timer wheel softirq processing.

   - Provide a mechanism to treat RTC implementations depending on their
     hardware properties, i.e. don't inflict the write at the 0.5
     seconds boundary which originates from the PC CMOS RTC to all RTCs.
     No functional change as drivers need to be updated separately.

   - The usual small updates to core code clocksource drivers. Nothing
     really exciting"

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (111 commits)
  timers: Add a function to start/reduce a timer
  pstore: Use ktime_get_real_fast_ns() instead of __getnstimeofday()
  timer: Prepare to change all DEFINE_TIMER() callbacks
  netfilter: ipvs: Convert timers to use timer_setup()
  scsi: qla2xxx: Convert timers to use timer_setup()
  block/aoe: discover_timer: Convert timers to use timer_setup()
  ide: Convert timers to use timer_setup()
  drbd: Convert timers to use timer_setup()
  mailbox: Convert timers to use timer_setup()
  crypto: Convert timers to use timer_setup()
  drivers/pcmcia: omap1: Fix error in automated timer conversion
  ARM: footbridge: Fix typo in timer conversion
  drivers/sgi-xp: Convert timers to use timer_setup()
  drivers/pcmcia: Convert timers to use timer_setup()
  drivers/memstick: Convert timers to use timer_setup()
  drivers/macintosh: Convert timers to use timer_setup()
  hwrng/xgene-rng: Convert timers to use timer_setup()
  auxdisplay: Convert timers to use timer_setup()
  sparc/led: Convert timers to use timer_setup()
  mips: ip22/32: Convert timers to use timer_setup()
  ...

2 files changed, 41 insertions, 15 deletions

diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index 2ed970d61da1..722d683e0b0f 100644
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -161,6 +161,9 @@ static struct rtc_device *rtc_allocate_device(void)
 
 	device_initialize(&rtc->dev);
 
+	/* Drivers can revise this default after allocating the device. */
+	rtc->set_offset_nsec =  NSEC_PER_SEC / 2;
+
 	rtc->irq_freq = 1;
 	rtc->max_user_freq = 64;
 	rtc->dev.class = rtc_class;
diff --git a/drivers/rtc/systohc.c b/drivers/rtc/systohc.c
index b4a68ffcd06b..0c177647ea6c 100644
--- a/drivers/rtc/systohc.c
+++ b/drivers/rtc/systohc.c
@@ -10,6 +10,7 @@
 /**
  * rtc_set_ntp_time - Save NTP synchronized time to the RTC
  * @now: Current time of day
+ * @target_nsec: pointer for desired now->tv_nsec value
  *
  * Replacement for the NTP platform function update_persistent_clock64
  * that stores time for later retrieval by rtc_hctosys.
@@ -18,30 +19,52 @@
  * possible at all, and various other -errno for specific temporary failure
  * cases.
  *
+ * -EPROTO is returned if now.tv_nsec is not close enough to *target_nsec.
+ (
  * If temporary failure is indicated the caller should try again 'soon'
  */
-int rtc_set_ntp_time(struct timespec64 now)
+int rtc_set_ntp_time(struct timespec64 now, unsigned long *target_nsec)
 {
 	struct rtc_device *rtc;
 	struct rtc_time tm;
+	struct timespec64 to_set;
 	int err = -ENODEV;
-
-	if (now.tv_nsec < (NSEC_PER_SEC >> 1))
-		rtc_time64_to_tm(now.tv_sec, &tm);
-	else
-		rtc_time64_to_tm(now.tv_sec + 1, &tm);
+	bool ok;
 
 	rtc = rtc_class_open(CONFIG_RTC_SYSTOHC_DEVICE);
-	if (rtc) {
-		/* rtc_hctosys exclusively uses UTC, so we call set_time here,
-		 * not set_mmss. */
-		if (rtc->ops &&
-		    (rtc->ops->set_time ||
-		     rtc->ops->set_mmss64 ||
-		     rtc->ops->set_mmss))
-			err = rtc_set_time(rtc, &tm);
-		rtc_class_close(rtc);
+	if (!rtc)
+		goto out_err;
+
+	if (!rtc->ops || (!rtc->ops->set_time && !rtc->ops->set_mmss64 &&
+			  !rtc->ops->set_mmss))
+		goto out_close;
+
+	/* Compute the value of tv_nsec we require the caller to supply in
+	 * now.tv_nsec.  This is the value such that (now +
+	 * set_offset_nsec).tv_nsec == 0.
+	 */
+	set_normalized_timespec64(&to_set, 0, -rtc->set_offset_nsec);
+	*target_nsec = to_set.tv_nsec;
+
+	/* The ntp code must call this with the correct value in tv_nsec, if
+	 * it does not we update target_nsec and return EPROTO to make the ntp
+	 * code try again later.
+	 */
+	ok = rtc_tv_nsec_ok(rtc->set_offset_nsec, &to_set, &now);
+	if (!ok) {
+		err = -EPROTO;
+		goto out_close;
 	}
 
+	rtc_time64_to_tm(to_set.tv_sec, &tm);
+
+	/* rtc_hctosys exclusively uses UTC, so we call set_time here, not
+	 * set_mmss.
+	 */
+	err = rtc_set_time(rtc, &tm);
+
+out_close:
+	rtc_class_close(rtc);
+out_err:
 	return err;
 }