Extend the range of the return value from nsecs_to_jiffies64() to support

Mesa's drm_syncobj usage, in the LinuxKPI.

While at it optimise the jiffies conversion functions to avoid repeated
and constant calculations.

Submitted by:	Greg V <greg@unrelenting.technology>
Differential Revision:	https://reviews.freebsd.org/D23846
MFC after:	1 week
Sponsored by:	Mellanox Technologies

sys/compat/linuxkpi/common/include/linux/jiffies.h

@@ -54,6 +54,18 @@
 
 #define	HZ	hz
 
+extern uint64_t lkpi_nsec2hz_rem;
+extern uint64_t lkpi_nsec2hz_div;
+extern uint64_t lkpi_nsec2hz_max;
+
+extern uint64_t lkpi_usec2hz_rem;
+extern uint64_t lkpi_usec2hz_div;
+extern uint64_t lkpi_usec2hz_max;
+
+extern uint64_t lkpi_msec2hz_rem;
+extern uint64_t lkpi_msec2hz_div;
+extern uint64_t lkpi_msec2hz_max;
+
 static inline int
 timespec_to_jiffies(const struct timespec *ts)
 {
@@ -70,12 +82,11 @@ timespec_to_jiffies(const struct timespec *ts)
 static inline int
 msecs_to_jiffies(uint64_t msec)
 {
-	uint64_t msec_max, result;
+	uint64_t result;
 
-	msec_max = -1ULL / (uint64_t)hz;
+	if (msec > lkpi_msec2hz_max)
-	if (msec > msec_max)
+		msec = lkpi_msec2hz_max;
-		msec = msec_max;
+	result = howmany(msec * lkpi_msec2hz_rem, lkpi_msec2hz_div);
-	result = howmany(msec * (uint64_t)hz, 1000ULL);
 	if (result > MAX_JIFFY_OFFSET)
 		result = MAX_JIFFY_OFFSET;
 
@@ -85,12 +96,11 @@ msecs_to_jiffies(uint64_t msec)
 static inline int
 usecs_to_jiffies(uint64_t usec)
 {
-	uint64_t usec_max, result;
+	uint64_t result;
 
-	usec_max = -1ULL / (uint64_t)hz;
+	if (usec > lkpi_usec2hz_max)
-	if (usec > usec_max)
+		usec = lkpi_usec2hz_max;
-		usec = usec_max;
+	result = howmany(usec * lkpi_usec2hz_rem, lkpi_usec2hz_div);
-	result = howmany(usec * (uint64_t)hz, 1000000ULL);
 	if (result > MAX_JIFFY_OFFSET)
 		result = MAX_JIFFY_OFFSET;
 
@@ -100,23 +110,24 @@ usecs_to_jiffies(uint64_t usec)
 static inline uint64_t
 nsecs_to_jiffies64(uint64_t nsec)
 {
-	uint64_t nsec_max, result;
 
-	nsec_max = -1ULL / (uint64_t)hz;
+	if (nsec > lkpi_nsec2hz_max)
-	if (nsec > nsec_max)
+		nsec = lkpi_nsec2hz_max;
-		nsec = nsec_max;
+	return (howmany(nsec * lkpi_nsec2hz_rem, lkpi_nsec2hz_div));
-	result = howmany(nsec * (uint64_t)hz, 1000000000ULL);
-	if (result > MAX_JIFFY_OFFSET)
-		result = MAX_JIFFY_OFFSET;
-
-	return (result);
 }
 
-static inline uint64_t
+static inline unsigned long
-nsecs_to_jiffies(uint64_t n)
+nsecs_to_jiffies(uint64_t nsec)
 {
 
-	return (usecs_to_jiffies(howmany(n, 1000ULL)));
+	if (sizeof(unsigned long) >= sizeof(uint64_t)) {
+		if (nsec > lkpi_nsec2hz_max)
+			nsec = lkpi_nsec2hz_max;
+	} else {
+		if (nsec > (lkpi_nsec2hz_max >> 32))
+			nsec = (lkpi_nsec2hz_max >> 32);
+	}
+	return (howmany(nsec * lkpi_nsec2hz_rem, lkpi_nsec2hz_div));
 }
 
 static inline uint64_t

sys/compat/linuxkpi/common/src/linux_compat.c

@@ -1934,9 +1934,38 @@ del_timer(struct timer_list *timer)
 	return (1);
 }
 
+/* greatest common divisor, Euclid equation */
+static uint64_t
+lkpi_gcd_64(uint64_t a, uint64_t b)
+{
+	uint64_t an;
+	uint64_t bn;
+
+	while (b != 0) {
+		an = b;
+		bn = a % b;
+		a = an;
+		b = bn;
+	}
+	return (a);
+}
+
+uint64_t lkpi_nsec2hz_rem;
+uint64_t lkpi_nsec2hz_div = 1000000000ULL;
+uint64_t lkpi_nsec2hz_max;
+
+uint64_t lkpi_usec2hz_rem;
+uint64_t lkpi_usec2hz_div = 1000000ULL;
+uint64_t lkpi_usec2hz_max;
+
+uint64_t lkpi_msec2hz_rem;
+uint64_t lkpi_msec2hz_div = 1000ULL;
+uint64_t lkpi_msec2hz_max;
+
 static void
 linux_timer_init(void *arg)
 {
+	uint64_t gcd;
 
 	/*
 	 * Compute an internal HZ value which can divide 2**32 to
@@ -1947,6 +1976,27 @@ linux_timer_init(void *arg)
 	while (linux_timer_hz_mask < (unsigned long)hz)
 		linux_timer_hz_mask *= 2;
 	linux_timer_hz_mask--;
+
+	/* compute some internal constants */
+	
+	lkpi_nsec2hz_rem = hz;
+	lkpi_usec2hz_rem = hz;
+	lkpi_msec2hz_rem = hz;
+
+	gcd = lkpi_gcd_64(lkpi_nsec2hz_rem, lkpi_nsec2hz_div);
+	lkpi_nsec2hz_rem /= gcd;
+	lkpi_nsec2hz_div /= gcd;
+	lkpi_nsec2hz_max = -1ULL / lkpi_nsec2hz_rem;
+
+	gcd = lkpi_gcd_64(lkpi_usec2hz_rem, lkpi_usec2hz_div);
+	lkpi_usec2hz_rem /= gcd;
+	lkpi_usec2hz_div /= gcd;
+	lkpi_usec2hz_max = -1ULL / lkpi_usec2hz_rem;
+
+	gcd = lkpi_gcd_64(lkpi_msec2hz_rem, lkpi_msec2hz_div);
+	lkpi_msec2hz_rem /= gcd;
+	lkpi_msec2hz_div /= gcd;
+	lkpi_msec2hz_max = -1ULL / lkpi_msec2hz_rem;
 }
 SYSINIT(linux_timer, SI_SUB_DRIVERS, SI_ORDER_FIRST, linux_timer_init, NULL);