wr_clocksource: Fix bug due to clock adjustment

The WR time adjustment was not taken into account in the driver. The
side effect was a big jump sometime of the monotonic clock used in PPSI
for the calculation of the timeouts. The side effect was that many
timeouts were firing too early.
The driver registration take now into account the adjustment and also
the calculation of the offset in the read() call.

kernel/wr_clocksource/wr_clocksource.c

@@ -24,6 +24,28 @@ static __iomem struct PPSG_WB *wrcs_ppsg;
 
 static int wrcs_is_registered; /* no need for atomic_t or whatever */
 
+/* prototypes */
+static int pps_gen_busy(void);
+static cycle_t wrcs_read(struct clocksource *cs);
+
+static struct clocksource wrcs_cs = {
+	.name = "white-rabbit",
+	.rating = 450,		/* perfect... */
+	.read = wrcs_read,
+	/* no enable/disable */
+	.mask = 0xffffffff, /* We fake a 32-bit thing */
+	.max_idle_ns = 900 * 1000 * 1000, /* well, 1s... */
+	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+
+static int pps_gen_busy(void)
+{
+	uint32_t cr = readl(&wrcs_ppsg->CR);
+	return cr & PPSG_CR_CNT_ADJ ? 0 : 1;
+}
+
+
 /* If so requested, print statistics once per second */
 static inline void wrcs_do_stats(void)
 {
@@ -46,41 +68,6 @@ static inline void wrcs_do_stats(void)
 	ncalls++;
 }
 
-DEFINE_SPINLOCK(wrcs_lock);
-
-static cycle_t wrcs_read(struct clocksource *cs)
-{
-	static uint32_t offset, last, this;
-	unsigned long flags;
-
-	wrcs_do_stats();
-
-	/* FIXME: identify a time jump by monitoring the tick counter */
-
-	/*
-	 * Turn the counter into a 32-bit one (see cs->mask below).
-	 * We reset at 0x3b9aca0, so without this we should use mask = 0x1f
-	 * and mac_idle = 32 ticks = 512ns. Unaffordable.
-	 */
-	spin_lock_irqsave(&wrcs_lock, flags);
-	this = readl(&wrcs_ppsg->CNTR_NSEC);
-	if (this < last)
-		offset += WRCS_FREQUENCY;
-	last = this;
-	spin_unlock_irqrestore(&wrcs_lock, flags);
-	return offset + this;
-}
-
-
-static struct clocksource wrcs_cs = {
-	.name = "white-rabbit",
-	.rating = 450,		/* perfect... */
-	.read = wrcs_read,
-	/* no enable/disable */
-	.mask = 0xffffffff, /* We fake a 32-bit thing */
-	.max_idle_ns = 900 * 1000 * 1000, /* well, 1s... */
-	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
-};
 
 /*
  * The timer is used to check when does WR synchronize.  When that
@@ -95,7 +82,16 @@ static void wrcs_timer_fn(unsigned long unused)
 	uint32_t ticks, tai_l, tai_h;
 	int64_t tai;
 
-	/* Read ppsg, all fields consistently se we can use the value */
+	if ( pps_gen_busy() ){
+		printk(KERN_DEBUG " %s: Adjusting in progress \n",__func__);
+		/* NS counter adjustment in progress. Try later */
+		goto retryLater;
+	}
+
+	wrcs_cs.rating=450; /* Perfect */
+
+	printk(KERN_DEBUG " %s: Timer function \n",__func__);
+	/* Read ppsg, all fields consistently so we can use the value */
 	do {
 		tai_l = readl(&wrcs_ppsg->CNTR_UTCLO);
 		tai_h = readl(&wrcs_ppsg->CNTR_UTCHI);
@@ -104,14 +100,50 @@ static void wrcs_timer_fn(unsigned long unused)
 	tai = (typeof(tai))tai_h << 32 | tai_l;
 
 	/* If we are before 2010 (date +%s --date=2010-01-01), try again */
-	if (tai < 1262300400LL) {
-		mod_timer(&wrcs_timer, jiffies + HZ);
-		return;
-	}
+	if (tai < 1262300400LL)
+		goto retryLater;
 
 	clocksource_register_hz(&wrcs_cs, WRCS_FREQUENCY);
 	wrcs_is_registered = 1;
 	/* And don't restart the timer */
+	return;
+
+retryLater:;
+	wrcs_cs.rating=450; /* Perfect */
+	mod_timer(&wrcs_timer, jiffies + HZ);
+	return;
+
+}
+
+DEFINE_SPINLOCK(wrcs_lock);
+
+static cycle_t wrcs_read(struct clocksource *cs)
+{
+	static uint32_t offset, last, this;
+	unsigned long flags;
+
+	wrcs_do_stats();
+
+	/* FIXME: identify a time jump by monitoring the tick counter */
+
+	/*
+	 * Turn the counter into a 32-bit one (see cs->mask below).
+	 * We reset at 0x3b9aca0, so without this we should use mask = 0x1f
+	 * and mac_idle = 32 ticks = 512ns. Unaffordable.
+	 */
+	spin_lock_irqsave(&wrcs_lock, flags);
+
+	this = readl(&wrcs_ppsg->CNTR_NSEC);
+	if ( this > NSEC_PER_SEC ) {
+		/* it means that the value is negative and an adjustment is in progress */
+		this=0; /* We freeze then the time */
+	} else {
+		if (this < last)
+			offset += WRCS_FREQUENCY;
+		last = this;
+	}
+	spin_unlock_irqrestore(&wrcs_lock, flags);
+	return offset + this;
 }
 
 static int wrcs_init(void)