1 files changed, 130 insertions, 1 deletions

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 4e18db1819f8..2fa87dcfeda9 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1195,6 +1195,108 @@ static bool timestamp_in_interval(u64 start, u64 end, u64 ts)
 	return false;
 }
 
+static bool convert_clock(u64 *val, u32 numerator, u32 denominator)
+{
+	u64 rem, res;
+
+	if (!numerator || !denominator)
+		return false;
+
+	res = div64_u64_rem(*val, denominator, &rem) * numerator;
+	*val = res + div_u64(rem * numerator, denominator);
+	return true;
+}
+
+static bool convert_base_to_cs(struct system_counterval_t *scv)
+{
+	struct clocksource *cs = tk_core.timekeeper.tkr_mono.clock;
+	struct clocksource_base *base;
+	u32 num, den;
+
+	/* The timestamp was taken from the time keeper clock source */
+	if (cs->id == scv->cs_id)
+		return true;
+
+	/*
+	 * Check whether cs_id matches the base clock. Prevent the compiler from
+	 * re-evaluating @base as the clocksource might change concurrently.
+	 */
+	base = READ_ONCE(cs->base);
+	if (!base || base->id != scv->cs_id)
+		return false;
+
+	num = scv->use_nsecs ? cs->freq_khz : base->numerator;
+	den = scv->use_nsecs ? USEC_PER_SEC : base->denominator;
+
+	if (!convert_clock(&scv->cycles, num, den))
+		return false;
+
+	scv->cycles += base->offset;
+	return true;
+}
+
+static bool convert_cs_to_base(u64 *cycles, enum clocksource_ids base_id)
+{
+	struct clocksource *cs = tk_core.timekeeper.tkr_mono.clock;
+	struct clocksource_base *base;
+
+	/*
+	 * Check whether base_id matches the base clock. Prevent the compiler from
+	 * re-evaluating @base as the clocksource might change concurrently.
+	 */
+	base = READ_ONCE(cs->base);
+	if (!base || base->id != base_id)
+		return false;
+
+	*cycles -= base->offset;
+	if (!convert_clock(cycles, base->denominator, base->numerator))
+		return false;
+	return true;
+}
+
+static bool convert_ns_to_cs(u64 *delta)
+{
+	struct tk_read_base *tkr = &tk_core.timekeeper.tkr_mono;
+
+	if (BITS_TO_BYTES(fls64(*delta) + tkr->shift) >= sizeof(*delta))
+		return false;
+
+	*delta = div_u64((*delta << tkr->shift) - tkr->xtime_nsec, tkr->mult);
+	return true;
+}
+
+/**
+ * ktime_real_to_base_clock() - Convert CLOCK_REALTIME timestamp to a base clock timestamp
+ * @treal:	CLOCK_REALTIME timestamp to convert
+ * @base_id:	base clocksource id
+ * @cycles:	pointer to store the converted base clock timestamp
+ *
+ * Converts a supplied, future realtime clock value to the corresponding base clock value.
+ *
+ * Return:  true if the conversion is successful, false otherwise.
+ */
+bool ktime_real_to_base_clock(ktime_t treal, enum clocksource_ids base_id, u64 *cycles)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned int seq;
+	u64 delta;
+
+	do {
+		seq = read_seqcount_begin(&tk_core.seq);
+		if ((u64)treal < tk->tkr_mono.base_real)
+			return false;
+		delta = (u64)treal - tk->tkr_mono.base_real;
+		if (!convert_ns_to_cs(&delta))
+			return false;
+		*cycles = tk->tkr_mono.cycle_last + delta;
+		if (!convert_cs_to_base(cycles, base_id))
+			return false;
+	} while (read_seqcount_retry(&tk_core.seq, seq));
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(ktime_real_to_base_clock);
+
 /**
  * get_device_system_crosststamp - Synchronously capture system/device timestamp
  * @get_time_fn:	Callback to get simultaneous device time and
@@ -1241,7 +1343,7 @@ int get_device_system_crosststamp(int (*get_time_fn)
 		 * installed timekeeper clocksource
 		 */
 		if (system_counterval.cs_id == CSID_GENERIC ||
-		    tk->tkr_mono.clock->id != system_counterval.cs_id)
+		    !convert_base_to_cs(&system_counterval))
 			return -ENODEV;
 		cycles = system_counterval.cycles;
 
@@ -1307,6 +1409,30 @@ int get_device_system_crosststamp(int (*get_time_fn)
 EXPORT_SYMBOL_GPL(get_device_system_crosststamp);
 
 /**
+ * timekeeping_clocksource_has_base - Check whether the current clocksource
+ *				      is based on given a base clock
+ * @id:		base clocksource ID
+ *
+ * Note:	The return value is a snapshot which can become invalid right
+ *		after the function returns.
+ *
+ * Return:	true if the timekeeper clocksource has a base clock with @id,
+ *		false otherwise
+ */
+bool timekeeping_clocksource_has_base(enum clocksource_ids id)
+{
+	/*
+	 * This is a snapshot, so no point in using the sequence
+	 * count. Just prevent the compiler from re-evaluating @base as the
+	 * clocksource might change concurrently.
+	 */
+	struct clocksource_base *base = READ_ONCE(tk_core.timekeeper.tkr_mono.clock->base);
+
+	return base ? base->id == id : false;
+}
+EXPORT_SYMBOL_GPL(timekeeping_clocksource_has_base);
+
+/**
  * do_settimeofday64 - Sets the time of day.
  * @ts:     pointer to the timespec64 variable containing the new time
  *
@@ -2421,6 +2547,7 @@ EXPORT_SYMBOL_GPL(random_get_entropy_fallback);
 
 /**
  * do_adjtimex() - Accessor function to NTP __do_adjtimex function
+ * @txc:	Pointer to kernel_timex structure containing NTP parameters
  */
 int do_adjtimex(struct __kernel_timex *txc)
 {
@@ -2489,6 +2616,8 @@ int do_adjtimex(struct __kernel_timex *txc)
 #ifdef CONFIG_NTP_PPS
 /**
  * hardpps() - Accessor function to NTP __hardpps function
+ * @phase_ts:	Pointer to timespec64 structure representing phase timestamp
+ * @raw_ts:	Pointer to timespec64 structure representing raw timestamp
  */
 void hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
 {