netdev - [patch V2 17/26] timekeeping: Provide time getters for auxiliary clocks

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Message-ID: <20250519083026.655171665@linutronix.de>
Date: Mon, 19 May 2025 10:33:35 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: netdev@...r.kernel.org,
 Richard Cochran <richardcochran@...il.com>,
 Christopher Hall <christopher.s.hall@...el.com>,
 John Stultz <jstultz@...gle.com>,
 Frederic Weisbecker <frederic@...nel.org>,
 Anna-Maria Behnsen <anna-maria@...utronix.de>,
 Miroslav Lichvar <mlichvar@...hat.com>,
 Werner Abt <werner.abt@...nberg-usa.com>,
 David Woodhouse <dwmw2@...radead.org>,
 Stephen Boyd <sboyd@...nel.org>,
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
 Kurt Kanzenbach <kurt@...utronix.de>,
 Nam Cao <namcao@...utronix.de>,
 Antoine Tenart <atenart@...nel.org>
Subject: [patch V2 17/26] timekeeping: Provide time getters for auxiliary
 clocks

Provide interfaces similar to the ktime_get*() family which provide access
to the auxiliary clocks.

These interfaces have a boolean return value, which indicates whether the
accessed clock is valid or not.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

---
 include/linux/timekeeping.h |   11 +++++++
 kernel/time/timekeeping.c   |   62 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)
---
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -263,6 +263,17 @@ extern bool timekeeping_rtc_skipresume(v
 
 extern void timekeeping_inject_sleeptime64(const struct timespec64 *delta);
 
+/*
+ * Auxiliary clock interfaces
+ */
+#ifdef CONFIG_POSIX_AUX_CLOCKS
+extern bool ktime_get_aux(clockid_t id, ktime_t *kt);
+extern bool ktime_get_aux_ts64(clockid_t id, struct timespec64 *kt);
+#else
+static inline bool ktime_get_aux(clockid_t id, ktime_t *kt) { return false; }
+static inline bool ktime_get_aux_ts64(clockid_t id, struct timespec64 *kt) { return false; }
+#endif
+
 /**
  * struct system_time_snapshot - simultaneous raw/real time capture with
  *				 counter value
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -2659,6 +2659,23 @@ EXPORT_SYMBOL(hardpps);
 /* Bitmap for the activated auxiliary timekeepers */
 static unsigned long aux_timekeepers;
 
+static inline bool aux_valid_clockid(clockid_t id)
+{
+	return id >= CLOCK_AUX && id <= CLOCK_AUX_LAST;
+}
+
+static inline unsigned int clockid_to_tkid(unsigned int id)
+{
+	return TIMEKEEPER_AUX + id - CLOCK_AUX;
+}
+
+static inline struct tk_data *aux_get_tk_data(clockid_t id)
+{
+	if (!aux_valid_clockid(id))
+		return NULL;
+	return &timekeeper_data[clockid_to_tkid(id)];
+}
+
 /* Invoked from timekeeping after a clocksource change */
 static void tk_aux_update_clocksource(void)
 {
@@ -2679,6 +2696,51 @@ static void tk_aux_update_clocksource(vo
 	}
 }
 
+/**
+ * ktime_get_aux - Get TAI time for a AUX clock
+ * @id:	ID of the clock to read (CLOCK_AUX...)
+ * @kt:	Pointer to ktime_t to store the time stamp
+ *
+ * Returns: True if the timestamp is valid, false otherwise
+ */
+bool ktime_get_aux(clockid_t id, ktime_t *kt)
+{
+	struct tk_data *tkd = aux_get_tk_data(id);
+	struct timekeeper *tk;
+	unsigned int seq;
+	ktime_t base;
+	u64 nsecs;
+
+	WARN_ON(timekeeping_suspended);
+
+	if (!tkd)
+		return false;
+
+	tk = &tkd->timekeeper;
+	do {
+		seq = read_seqcount_begin(&tkd->seq);
+		if (!tk->clock_valid)
+			return false;
+
+		base = ktime_add(tk->tkr_mono.base, tk->offs_aux);
+		nsecs = timekeeping_get_ns(&tk->tkr_mono);
+	} while (read_seqcount_retry(&tkd->seq, seq));
+
+	*kt = ktime_add_ns(base, nsecs);
+	return true;
+}
+EXPORT_SYMBOL_GPL(ktime_get_aux);
+
+bool ktime_get_aux_ts64(clockid_t id, struct timespec64 *ts)
+{
+	ktime_t now;
+
+	if (!ktime_get_aux(id, &now))
+		return false;
+	*ts = ktime_to_timespec64(now);
+	return true;
+}
+
 static __init void tk_aux_setup(void)
 {
 	for (int i = TIMEKEEPER_AUX; i <= TIMEKEEPER_AUX_LAST; i++)