Subject: [patch V2 11/25] timekeeping: Add CLOCK ID to system_device_crosststamp

From: Thomas Gleixner <[email-masked]>
Date: Fri, 29 May 2026 22:00:32 +0200

From: Thomas Gleixner <[email-masked]>

The normal capture for system/device cross timestamps is CLOCK_REALTIME,
but that's meaningless for AUX clocks.

Add a clock_id field to struct system_device_crosststamp and initialize it
with CLOCK_REALTIME at the two places which prepare for cross
timestamps.

After the related code has been cleaned up, the core code will honor the
clock_id field when calculating the system time from the system counter
snapshot.

No functional change.

Signed-off-by: Thomas Gleixner <[email-masked]>
Tested-by: David Woodhouse <[email-masked]>
Tested-by: Arthur Kiyanovski <[email-masked]>
Reviewed-by: David Woodhouse <[email-masked]>
Reviewed-by: Jacob Keller <[email-masked]>
---
 drivers/ptp/ptp_chardev.c     |    2 +-
 include/linux/timekeeping.h   |    2 ++
 sound/hda/common/controller.c |    2 +-
 3 files changed, 4 insertions(+), 2 deletions(-)
--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c
@@ -317,8 +317,8 @@ typedef int (*ptp_crosststamp_fn)(struct
 static long ptp_sys_offset_precise(struct ptp_clock *ptp, void __user *arg,
 				   ptp_crosststamp_fn crosststamp_fn)
 {
+	struct system_device_crosststamp xtstamp = { .clock_id = CLOCK_REALTIME };
 	struct ptp_sys_offset_precise precise_offset;
-	struct system_device_crosststamp xtstamp;
 	struct timespec64 ts;
 	int err;
 
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -315,12 +315,14 @@ struct system_counterval_t {
 /**
  * struct system_device_crosststamp - system/device cross-timestamp
  *				      (synchronized capture)
+ * @clock_id:		System time Clock ID to capture
  * @device:		Device time
  * @sys_counter:	Clocksource counter value simultaneous with device time
  * @sys_realtime:	Realtime simultaneous with device time
  * @sys_monoraw:	Monotonic raw simultaneous with device time
  */
 struct system_device_crosststamp {
+	clockid_t			clock_id;
 	ktime_t				device;
 	struct system_counterval_t	sys_counter;
 	ktime_t				sys_realtime;
--- a/sound/hda/common/controller.c
+++ b/sound/hda/common/controller.c
@@ -489,9 +489,9 @@ static int azx_get_time_info(struct snd_
 			struct snd_pcm_audio_tstamp_config *audio_tstamp_config,
 			struct snd_pcm_audio_tstamp_report *audio_tstamp_report)
 {
+	struct system_device_crosststamp xtstamp = { .clock_id = CLOCK_REALTIME };
 	struct azx_dev *azx_dev = get_azx_dev(substream);
 	struct snd_pcm_runtime *runtime = substream->runtime;
-	struct system_device_crosststamp xtstamp;
 	int ret;
 	u64 nsec;