timekeeping: Provide ktime_get_snapshot_id()

ktime_get_snapshot() provides a snapshot of the underlying clocksource
counter value and the corresponding CLOCK_MONOTONIC_RAW, CLOCK_REALTIME and
CLOCK_BOOTTIME timestamps.

There is no usage of CLOCK_REALTIME and CLOCK_BOOTTIME at the same time and
CLOCK_BOOTTIME support was just added for the ARM64 KVM tracing mechanism,
which needs CLOCK_BOOTTIME and the underlying clocksource counter value.

ktime_get_snapshot() is also not suitable for usage with CLOCK_AUX, but
that's a prerequisite to support PTP hardware timestamping for CLOCK_AUX
steering.

As a first step, rename ktime_get_snapshot() to ktime_get_snapshot_id(),
which now takes a clockid argument to select the clock which needs to be
captured. The result is stored in system_time_snapshot::systime, which will
replace the system_time_snapshot::real/boot members once all usage sites
have been converted.

ktime_get_snapshot() is a simple wrapper which hands in CLOCK_REALTIME as
clockid argument for the conversion period. That means CLOCK_REALTIME is
now captured twice, but that redunancy is only temporary.

As all usage sites of struct system_time_snapshot has to be updated anyway,
rename the 'raw' member to 'monoraw' for clarity.

No functional change vs. current users of ktime_get_snapshot()

Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: David Woodhouse <dwmw@amazon.co.uk>
Tested-by: Arthur Kiyanovski <akiyano@amazon.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20260529195556.971591633@kernel.org

1 files changed, 24 insertions, 10 deletions

diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index aee2c1a46e47..161157c8d27e 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -276,24 +276,32 @@ static inline bool ktime_get_aux_ts64(clockid_t id, struct timespec64 *kt) { ret
 #endif
 
 /**
- * struct system_time_snapshot - simultaneous raw/real time capture with
- *				 counter value
- * @cycles:	Clocksource counter value to produce the system times
- * @real:	Realtime system time
- * @boot:	Boot time
- * @raw:	Monotonic raw system time
- * @cs_id:	Clocksource ID
+ * struct system_time_snapshot - Simultaneous time capture of CLOCK_MONOTONIC_RAW,
+ *				 a selected CLOCK_* and the clocksource counter value
+ * @cycles:		Clocksource counter value to produce the system times
+ * @systime:		The system time of the selected CLOCK ID
+ * @real:		Realtime system time
+ * @boot:		Boot time
+ * @raw:		Monotonic raw system time
+ * @monoraw:		Monotonic raw system time
+ * @cs_id:		Clocksource ID
  * @clock_was_set_seq:	The sequence number of clock-was-set events
  * @cs_was_changed_seq:	The sequence number of clocksource change events
+ * @valid:		True if the snapshot is valid
  */
 struct system_time_snapshot {
 	u64			cycles;
+	ktime_t			systime;
 	ktime_t			real;
 	ktime_t			boot;
-	ktime_t			raw;
+	union {
+		ktime_t		raw;
+		ktime_t		monoraw;
+	};
 	enum clocksource_ids	cs_id;
 	unsigned int		clock_was_set_seq;
 	u8			cs_was_changed_seq;
+	u8			valid;
 };
 
 /**
@@ -341,9 +349,15 @@ extern int get_device_system_crosststamp(
 			struct system_device_crosststamp *xtstamp);
 
 /*
- * Simultaneously snapshot realtime and monotonic raw clocks
+ * Simultaneously snapshot a given clock with MONOTONIC_RAW and the underlying
+ * clocksource counter value.
  */
-extern void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot);
+extern void ktime_get_snapshot_id(clockid_t clock_id, struct system_time_snapshot *systime_snapshot);
+
+static inline void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
+{
+	ktime_get_snapshot_id(CLOCK_REALTIME, systime_snapshot);
+}
 
 /*
  * Persistent clock related interfaces