Re: [patch V2 00/25] timekeeping/ptp: Expand snapshot functionality

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, May 29, 2026 at 09:59:47PM +0200, Thomas Gleixner wrote:
> This is an update to V1 which can be found here:
> 
>    https://lore.kernel.org/lkml/20260526165826.392227559@kernel.org
> 
> PTP wants to grow new snapshot functionality, which provides not only the
> captured CLOCK* values, but also the underlying clocksource counter value.
> 
>    https://lore.kernel.org/20260515164033.6403-1-akiyano@amazon.com
> 
> There was quite some discussion in seemingly related threads how to capture
> these values and how to provide core infrastructure so that driver writers
> have something to work with
> 
>    https://lore.kernel.org/20260514225842.110706-1-hramamurthy@google.com
>    https://lore.kernel.org/20260520135207.37826-1-dwmw2@infradead.org


virtio bits:

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> This series implements the timekeeping related mechanisms to:
> 
>      1) Capture CLOCK values along with the clocksource counter value for
>      	non-hardware based sampling
> 
>      2) Expanding the hardware cross time stamp mechanism to hand back the
>      	clocksource counter value, which was captured by the device, along
>      	with the related CLOCK values
> 
>      3) Adding AUX clock support to the hardware cross timestamping core
> 
>      4) Add support for derived clocksources to the snapshot mechanism (New
>      	in V2)
> 
> Changes vs. V1:
> 
>   - Fixed the ptp_ocp typo - 0-day, Jakub
> 
>   - Renamed the system_time_snapshot members sys and raw so systime and
>     monoraw to make them less ambigous.
> 
>   - Fixed the error case return values of get_device_system_crosststamp()
> 
>   - Made ktime_snapshot_id() void as there is no point for the return
>     value, which is nowhere checked and cannot be propagated.
>     system_time_snapshot::valid has to be evaluated at the call sites
>     anyway. - Jacob
> 
>   - Picked up the first patch from Davids follow up series, which extends
>     the snapshot mechanism so that derived clocksources (like kvmclock and
>     Hyper-V scaled TSC) can return the actual underlying hardware counter
>     value (TSC for the two examples).
> 
>   - Collected Reviewed/Acked/Tested-by tags
> 
> Delta patch against v1 below.
> 
> The series is based on v7.1-rc2 and also available from git:
> 
>     git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git timekeeping-ptp-extend-v2
> 
> Thanks,
> 
> 	tglx
> ---
> diff --git a/arch/arm64/kvm/hyp_trace.c b/arch/arm64/kvm/hyp_trace.c
> index 616062587510..b056c652ff01 100644
> --- a/arch/arm64/kvm/hyp_trace.c
> +++ b/arch/arm64/kvm/hyp_trace.c
> @@ -51,8 +51,8 @@ static void __hyp_clock_work(struct work_struct *work)
>  
>  	hyp_clock = container_of(dwork, struct hyp_trace_clock, work);
>  
> -	ktime_get_snapshot_id(&snap, CLOCK_BOOTTIME);
> -	boot = ktime_to_ns(snap.sys);
> +	ktime_get_snapshot_id(CLOCK_BOOTTIME, &snap);
> +	boot = ktime_to_ns(snap.systime);
>  
>  	delta_boot = boot - hyp_clock->boot;
>  	delta_cycles = snap.cycles - hyp_clock->cycles;
> @@ -120,7 +120,7 @@ static void hyp_trace_clock_enable(struct hyp_trace_clock *hyp_clock, bool enabl
>  
>  	ktime_get_snapshot_id(&snap, CLOCK_BOOTTIME);
>  
> -	hyp_clock->boot = ktime_to_ns(snap.sys);
> +	hyp_clock->boot = ktime_to_ns(snap.systime);
>  	hyp_clock->cycles = snap.cycles;
>  	hyp_clock->mult = 0;
>  
> diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
> index e60cc7ed3e70..b11b8821c9fb 100644
> --- a/arch/arm64/kvm/hypercalls.c
> +++ b/arch/arm64/kvm/hypercalls.c
> @@ -28,7 +28,7 @@ static void kvm_ptp_get_time(struct kvm_vcpu *vcpu, u64 *val)
>  	 * system time and counter value must captured at the same
>  	 * time to keep consistency and precision.
>  	 */
> -	ktime_get_snapshot_id(&systime_snapshot, CLOCK_REALTIME);
> +	ktime_get_snapshot_id(CLOCK_REALTIME, &systime_snapshot);
>  
>  	/*
>  	 * This is only valid if the current clocksource is the
> @@ -61,8 +61,8 @@ static void kvm_ptp_get_time(struct kvm_vcpu *vcpu, u64 *val)
>  	 * in the future (about 292 years from 1970, and at that stage
>  	 * nobody will give a damn about it).
>  	 */
> -	val[0] = upper_32_bits(systime_snapshot.sys);
> -	val[1] = lower_32_bits(systime_snapshot.sys);
> +	val[0] = upper_32_bits(systime_snapshot.systime);
> +	val[1] = lower_32_bits(systime_snapshot.systime);
>  	val[2] = upper_32_bits(cycles);
>  	val[3] = lower_32_bits(cycles);
>  }
> diff --git a/drivers/net/dsa/sja1105/sja1105_main.c b/drivers/net/dsa/sja1105/sja1105_main.c
> index 1d5fef4df560..2697073dbf90 100644
> --- a/drivers/net/dsa/sja1105/sja1105_main.c
> +++ b/drivers/net/dsa/sja1105/sja1105_main.c
> @@ -2310,10 +2310,10 @@ int sja1105_static_config_reload(struct sja1105_private *priv,
>  		goto out;
>  	}
>  
> -	t1 = ktime_to_ns(ptp_sts_before.pre_sts.sys);
> -	t2 = ktime_to_ns(ptp_sts_before.post_sts.sys);
> -	t3 = ktime_to_ns(ptp_sts_after.pre_sts.sys);
> -	t4 = ktime_to_ns(ptp_sts_after.post_sts.sys);
> +	t1 = ktime_to_ns(ptp_sts_before.pre_sts.systime);
> +	t2 = ktime_to_ns(ptp_sts_before.post_sts.systime);
> +	t3 = ktime_to_ns(ptp_sts_after.pre_sts.systime);
> +	t4 = ktime_to_ns(ptp_sts_after.post_sts.systime);
>  	/* Mid point, corresponds to pre-reset PTPCLKVAL */
>  	t12 = t1 + (t2 - t1) / 2;
>  	/* Mid point, corresponds to post-reset PTPCLKVAL, aka 0 */
> diff --git a/drivers/net/ethernet/intel/ice/ice_ptp.c b/drivers/net/ethernet/intel/ice/ice_ptp.c
> index 5023fc1587f9..f9e4ec6f7ebb 100644
> --- a/drivers/net/ethernet/intel/ice/ice_ptp.c
> +++ b/drivers/net/ethernet/intel/ice/ice_ptp.c
> @@ -2117,7 +2117,7 @@ static int ice_capture_crosststamp(ktime_t *device,
>  	}
>  
>  	/* Snapshot system time for historic interpolation */
> -	ktime_get_snapshot_id(&ctx->snapshot, ctx->snapshot_clock_id);
> +	ktime_get_snapshot_id(ctx->snapshot_clock_id, &ctx->snapshot);
>  
>  	/* Program cmd to master timer */
>  	ice_ptp_src_cmd(hw, ICE_PTP_READ_TIME);
> diff --git a/drivers/net/ethernet/intel/igc/igc_ptp.c b/drivers/net/ethernet/intel/igc/igc_ptp.c
> index 9b8b4a04e32d..b40aba9ab685 100644
> --- a/drivers/net/ethernet/intel/igc/igc_ptp.c
> +++ b/drivers/net/ethernet/intel/igc/igc_ptp.c
> @@ -1049,7 +1049,7 @@ static int igc_phc_get_syncdevicetime(ktime_t *device,
>  	 */
>  	do {
>  		/* Get a snapshot of system clocks to use as historic value. */
> -		ktime_get_snapshot_id(&adapter->snapshot, adapter->snapshot_clock_id);
> +		ktime_get_snapshot_id(adapter->snapshot_clock_id, &adapter->snapshot);
>  
>  		igc_ptm_trigger(hw);
>  
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
> index beb80912b9d5..5df786133e4b 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
> @@ -340,7 +340,7 @@ static int mlx5_ptp_getcrosststamp(struct ptp_clock_info *ptp,
>  		goto unlock;
>  	}
>  
> -	ktime_get_snapshot_id(&history_begin, cts->clock_id);
> +	ktime_get_snapshot_id(cts->clock_id, &history_begin);
>  
>  	err = get_device_system_crosststamp(mlx5_mtctr_syncdevicetime, mdev,
>  					    &history_begin, cts);
> @@ -366,7 +366,7 @@ static int mlx5_ptp_getcrosscycles(struct ptp_clock_info *ptp,
>  		goto unlock;
>  	}
>  
> -	ktime_get_snapshot_id(&history_begin, cts->clock_id);
> +	ktime_get_snapshot_id(cts->clock_id, &history_begin);
>  
>  	err = get_device_system_crosststamp(mlx5_mtctr_syncdevicecyclestime,
>  					    mdev, &history_begin, cts);
> diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
> index aed5c13cd1be..dc23cd708cfe 100644
> --- a/drivers/ptp/ptp_chardev.c
> +++ b/drivers/ptp/ptp_chardev.c
> @@ -392,11 +392,11 @@ static long ptp_sys_offset_extended(struct ptp_clock *ptp, void __user *arg,
>  		extoff->ts[i][1].sec = ts.tv_sec;
>  		extoff->ts[i][1].nsec = ts.tv_nsec;
>  
> -		ts = ktime_to_timespec64(sts.pre_sts.sys);
> +		ts = ktime_to_timespec64(sts.pre_sts.systime);
>  		extoff->ts[i][0].sec = ts.tv_sec;
>  		extoff->ts[i][0].nsec = ts.tv_nsec;
>  
> -		ts = ktime_to_timespec64(sts.post_sts.sys);
> +		ts = ktime_to_timespec64(sts.post_sts.systime);
>  		extoff->ts[i][2].sec = ts.tv_sec;
>  		extoff->ts[i][2].nsec = ts.tv_nsec;
>  	}
> diff --git a/drivers/ptp/ptp_ocp.c b/drivers/ptp/ptp_ocp.c
> index b7a23936a44d..28b0302c6250 100644
> --- a/drivers/ptp/ptp_ocp.c
> +++ b/drivers/ptp/ptp_ocp.c
> @@ -1492,7 +1492,7 @@ __ptp_ocp_gettime_locked(struct ptp_ocp *bp, struct timespec64 *ts,
>  	ptp_read_system_postts(sts);
>  
>  	if (sts && bp->ts_window_adjust)
> -		sts->post_ts.sys -= bp->ts_window_adjust;
> +		sts->post_sts.systime -= bp->ts_window_adjust;
>  
>  	time_ns = ioread32(&bp->reg->time_ns);
>  	time_sec = ioread32(&bp->reg->time_sec);
> @@ -4592,8 +4592,8 @@ ptp_ocp_summary_show(struct seq_file *s, void *data)
>  		struct timespec64 sys_ts;
>  		s64 pre_ns, post_ns, ns;
>  
> -		pre_ns = ktime_to_ns(sts.pre_sts.sys);
> -		post_ns = ktime_to_ns(sts.post_sts.sys);
> +		pre_ns = ktime_to_ns(sts.pre_sts.systime);
> +		post_ns = ktime_to_ns(sts.post_sts.systime);
>  		ns = (pre_ns + post_ns) / 2;
>  		ns += (s64)bp->utc_tai_offset * NSEC_PER_SEC;
>  		sys_ts = ns_to_timespec64(ns);
> diff --git a/drivers/ptp/ptp_vmclock.c b/drivers/ptp/ptp_vmclock.c
> index cb18c15a4697..d6a5a533164a 100644
> --- a/drivers/ptp/ptp_vmclock.c
> +++ b/drivers/ptp/ptp_vmclock.c
> @@ -263,7 +263,7 @@ static int ptp_vmclock_getcrosststamp(struct ptp_clock_info *ptp,
>  	if (ret == -ENODEV) {
>  		struct system_time_snapshot systime_snapshot;
>  
> -		ktime_get_snapshot_id(&systime_snapshot, CLOCK_REALTIME);
> +		ktime_get_snapshot_id(CLOCK_REALTIME, &systime_snapshot);
>  
>  		if (systime_snapshot.cs_id == CSID_X86_TSC ||
>  		    systime_snapshot.cs_id == CSID_X86_KVM_CLK) {
> diff --git a/drivers/virtio/virtio_rtc_ptp.c b/drivers/virtio/virtio_rtc_ptp.c
> index e15d00aeb01d..ff8d834493dc 100644
> --- a/drivers/virtio/virtio_rtc_ptp.c
> +++ b/drivers/virtio/virtio_rtc_ptp.c
> @@ -139,7 +139,7 @@ static int viortc_ptp_getcrosststamp(struct ptp_clock_info *ptp,
>  	if (ret)
>  		return ret;
>  
> -	ktime_get_snapshot_id(&history_begin, xtstamp->clock_id);
> +	ktime_get_snapshot_id(xtstamp->clock_id, &history_begin);
>  	if (history_begin.cs_id != cs_id)
>  		return -EOPNOTSUPP;
>  
> diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
> index 7c38190b10bf..6d9ddf1587a2 100644
> --- a/include/linux/clocksource.h
> +++ b/include/linux/clocksource.h
> @@ -31,6 +31,21 @@ struct module;
>  
>  #include <vdso/clocksource.h>
>  
> +/**
> + * struct clocksource_hw_snapshot - Snapshot for the underlying hardware counter of derived
> + *				    clocksources like kvmclock or Hyper-V scaled TSC
> + * @hw_cycles:		The hardware counter value
> + * @hw_csid:		Clocksource ID of the hardware counter
> + *
> + * Such clocksources must implement the read_snapshot() callback and fill in the
> + * hardware counter value, the clocksource ID of the hardware counter and derive
> + * the actual clocksource cycles from @hw_cycles to provide an atomic snapshot
> + */
> +struct clocksource_hw_snapshot {
> +	u64			hw_cycles;
> +	enum clocksource_ids	hw_csid;
> +};
> +
>  /**
>   * struct clocksource - hardware abstraction for a free running counter
>   *	Provides mostly state-free accessors to the underlying hardware.
> @@ -72,6 +87,14 @@ struct module;
>   * @flags:		Flags describing special properties
>   * @base:		Hardware abstraction for clock on which a clocksource
>   *			is based
> + * @read_snapshot:	Extended @read() function for clocksources such as
> + *			kvmclock or the Hyper-V scaled TSC where the actual
> + *			clocksource value for timekeeping is calculated from an
> + *			underlying hardware counter. Returns the timekeeping
> + *			relevant cycle value and stores the raw value of the
> + *			underlying counter from which it was calculated
> + *			including the clocksource ID of that counter in the
> + *			clocksource hardware snapshot.
>   * @enable:		Optional function to enable the clocksource
>   * @disable:		Optional function to disable the clocksource
>   * @suspend:		Optional suspend function for the clocksource
> @@ -113,6 +136,7 @@ struct clocksource {
>  	unsigned long		flags;
>  	struct clocksource_base *base;
>  
> +	u64			(*read_snapshot)(struct clocksource *cs, struct clocksource_hw_snapshot *chs);
>  	int			(*enable)(struct clocksource *cs);
>  	void			(*disable)(struct clocksource *cs);
>  	void			(*suspend)(struct clocksource *cs);
> diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h
> index cd80f1cb96a9..9f088c9023b1 100644
> --- a/include/linux/pps_kernel.h
> +++ b/include/linux/pps_kernel.h
> @@ -102,9 +102,9 @@ static inline void pps_get_ts(struct pps_event_time *ts)
>  #ifdef CONFIG_NTP_PPS
>  	struct system_time_snapshot snap;
>  
> -	ktime_get_snapshot_id(&snap, CLOCK_REALTIME);
> -	ts->ts_real = ktime_to_timespec64(snap.sys);
> -	ts->ts_raw = ktime_to_timespec64(snap.raw);
> +	ktime_get_snapshot_id(CLOCK_REALTIME, &snap);
> +	ts->ts_real = ktime_to_timespec64(snap.systime);
> +	ts->ts_raw = ktime_to_timespec64(snap.monoraw);
>  #else
>  	ktime_get_real_ts64(&ts->ts_real);
>  #endif
> diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h
> index df6c9aac458b..36a27a910595 100644
> --- a/include/linux/ptp_clock_kernel.h
> +++ b/include/linux/ptp_clock_kernel.h
> @@ -511,13 +511,13 @@ static inline ktime_t ptp_convert_timestamp(const ktime_t *hwtstamp,
>  static inline void ptp_read_system_prets(struct ptp_system_timestamp *sts)
>  {
>  	if (sts)
> -		ktime_get_snapshot_id(&sts->pre_sts, sts->clockid);
> +		ktime_get_snapshot_id(sts->clockid, &sts->pre_sts);
>  }
>  
>  static inline void ptp_read_system_postts(struct ptp_system_timestamp *sts)
>  {
>  	if (sts)
> -		ktime_get_snapshot_id(&sts->post_sts, sts->clockid);
> +		ktime_get_snapshot_id(sts->clockid, &sts->post_sts);
>  }
>  
>  #endif
> diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
> index f7945f1048fc..984a866d293b 100644
> --- a/include/linux/timekeeping.h
> +++ b/include/linux/timekeeping.h
> @@ -279,18 +279,24 @@ static inline bool ktime_get_aux_ts64(clockid_t id, struct timespec64 *kt) { ret
>   * 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
> - * @sys:		The system time of the selected CLOCK ID
> - * @raw:		Monotonic raw system time
> + * @hw_cycles:		For derived clocksources, the hardware counter value from
> + *			which @cycles was derived
> + * @systime:		The system time of the selected CLOCK ID
> + * @monoraw:		Monotonic raw system time
>   * @cs_id:		Clocksource ID
> + * @hw_csid:		Clocksource ID of the underlying hardware counter for derived
> + *			clocksources which implement the read_snapshot() callback.
>   * @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			sys;
> -	ktime_t			raw;
> +	u64			hw_cycles;
> +	ktime_t			systime;
> +	ktime_t			monoraw;
>  	enum clocksource_ids	cs_id;
> +	enum clocksource_ids	hw_csid;
>  	unsigned int		clock_was_set_seq;
>  	u8			cs_was_changed_seq;
>  	u8			valid;
> @@ -348,8 +354,7 @@ extern int get_device_system_crosststamp(
>   * Simultaneously snapshot a given clock with MONOTONIC_RAW and the underlying
>   * clocksource counter value.
>   */
> -extern bool ktime_get_snapshot_id(struct system_time_snapshot *systime_snapshot,
> -				  clockid_t clock_id);
> +extern void ktime_get_snapshot_id(clockid_t clock_id, struct system_time_snapshot *systime_snapshot);
>  
>  /*
>   * Persistent clock related interfaces
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> index c4fd7229b7da..0d5b67f609bb 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -320,6 +320,7 @@ static __always_inline u64 tk_clock_read(const struct tk_read_base *tkr)
>  
>  	return clock->read(clock);
>  }
> +
>  static inline void clocksource_disable_inline_read(void) { }
>  static inline void clocksource_enable_inline_read(void) { }
>  #endif
> @@ -1187,14 +1188,26 @@ noinstr time64_t __ktime_get_real_seconds(void)
>  	return tk->xtime_sec;
>  }
>  
> +static inline u64 tk_clock_read_snapshot(const struct tk_read_base *tkr,
> +					 struct clocksource_hw_snapshot *chs)
> +{
> +	struct clocksource *clock = READ_ONCE(tkr->clock);
> +
> +	if (unlikely(clock->read_snapshot))
> +		return clock->read_snapshot(clock, chs);
> +
> +	return clock->read(clock);
> +}
> +
> +
>  /**
>   * ktime_get_snapshot_id -  Simultaneously snapshot a given clock ID with
>   *			    CLOCK_MONOTONIC_RAW and the underlying
>   *			    clocksource counter value.
> - * @systime_snapshot:	Pointer to struct receiving the system time snapshot
>   * @clock_id:		The clock ID to snapshot
> + * @systime_snapshot:	Pointer to struct receiving the system time snapshot
>   */
> -bool ktime_get_snapshot_id(struct system_time_snapshot *systime_snapshot, clockid_t clock_id)
> +void ktime_get_snapshot_id(clockid_t clock_id, struct system_time_snapshot *systime_snapshot)
>  {
>  	ktime_t base_raw, base_sys, offs_sys, *offs, offs_zero = 0;
>  	u64 nsec_raw, nsec_sys, now;
> @@ -1206,7 +1219,7 @@ bool ktime_get_snapshot_id(struct system_time_snapshot *systime_snapshot, clocki
>  	systime_snapshot->valid = false;
>  
>  	if (WARN_ON_ONCE(timekeeping_suspended))
> -		return false;
> +		return;
>  
>  	switch (clock_id) {
>  	case CLOCK_REALTIME:
> @@ -1226,25 +1239,31 @@ bool ktime_get_snapshot_id(struct system_time_snapshot *systime_snapshot, clocki
>  	case CLOCK_AUX ... CLOCK_AUX_LAST:
>  		tkd = aux_get_tk_data(clock_id);
>  		if (!tkd)
> -			return false;
> +			return;
>  		offs = &tkd->timekeeper.offs_aux;
>  		break;
>  	default:
>  		WARN_ON_ONCE(1);
> -		return false;
> +		return;
>  	}
>  
>  	tk = &tkd->timekeeper;
>  
>  	do {
> +		struct clocksource_hw_snapshot chs = { };
> +
>  		seq = read_seqcount_begin(&tkd->seq);
>  
>  		/* Aux clocks can be invalid */
>  		if (!tk->clock_valid)
> -			return false;
> +			return;
>  
> -		now = tk_clock_read(&tk->tkr_mono);
> +		now = tk_clock_read_snapshot(&tk->tkr_mono, &chs);
>  		systime_snapshot->cs_id = tk->tkr_mono.clock->id;
> +
> +		systime_snapshot->hw_cycles = chs.hw_cycles;
> +		systime_snapshot->hw_csid = chs.hw_csid;
> +
>  		systime_snapshot->cs_was_changed_seq = tk->cs_was_changed_seq;
>  		systime_snapshot->clock_was_set_seq = tk->clock_was_set_seq;
>  
> @@ -1257,18 +1276,17 @@ bool ktime_get_snapshot_id(struct system_time_snapshot *systime_snapshot, clocki
>  	} while (read_seqcount_retry(&tkd->seq, seq));
>  
>  	systime_snapshot->cycles = now;
> -	systime_snapshot->sys = ktime_add_ns(base_sys, offs_sys + nsec_sys);
> -	systime_snapshot->raw = ktime_add_ns(base_raw, nsec_raw);
> +	systime_snapshot->systime = ktime_add_ns(base_sys, offs_sys + nsec_sys);
> +	systime_snapshot->monoraw = ktime_add_ns(base_raw, nsec_raw);
>  
>  	/*
>  	 * Special case for PTP. Just transfer the raw time into sys,
> -	 * so the call sites can consistently use snap::sys.
> +	 * so the call sites can consistently use snap::systime.
>  	 */
>  	if (clock_id == CLOCK_MONOTONIC_RAW)
> -		systime_snapshot->sys = systime_snapshot->raw;
> +		systime_snapshot->systime = systime_snapshot->monoraw;
>  	/* Tell the consumer that this snapshot is valid */
>  	systime_snapshot->valid = true;
> -	return true;
>  }
>  EXPORT_SYMBOL_GPL(ktime_get_snapshot_id);
>  
> @@ -1330,7 +1348,7 @@ static int adjust_historical_crosststamp(struct system_time_snapshot *history,
>  	 * Scale the monotonic raw time delta by:
>  	 *	partial_history_cycles / total_history_cycles
>  	 */
> -	corr_raw = (u64)ktime_to_ns(ktime_sub(ts->sys_monoraw, history->raw));
> +	corr_raw = (u64)ktime_to_ns(ktime_sub(ts->sys_monoraw, history->monoraw));
>  	ret = scale64_check_overflow(partial_history_cycles,
>  				     total_history_cycles, &corr_raw);
>  	if (ret)
> @@ -1347,7 +1365,7 @@ static int adjust_historical_crosststamp(struct system_time_snapshot *history,
>  	if (discontinuity) {
>  		corr_sys = mul_u64_u32_div(corr_raw, tk->tkr_mono.mult, tk->tkr_raw.mult);
>  	} else {
> -		corr_sys = (u64)ktime_to_ns(ktime_sub(ts->sys_systime, history->sys));
> +		corr_sys = (u64)ktime_to_ns(ktime_sub(ts->sys_systime, history->systime));
>  		ret = scale64_check_overflow(partial_history_cycles, total_history_cycles,
>  					     &corr_sys);
>  		if (ret)
> @@ -1356,8 +1374,8 @@ static int adjust_historical_crosststamp(struct system_time_snapshot *history,
>  
>  	/* Fixup monotonic raw and system time time values */
>  	if (interp_forward) {
> -		ts->sys_monoraw = ktime_add_ns(history->raw, corr_raw);
> -		ts->sys_systime = ktime_add_ns(history->sys, corr_sys);
> +		ts->sys_monoraw = ktime_add_ns(history->monoraw, corr_raw);
> +		ts->sys_systime = ktime_add_ns(history->systime, corr_sys);
>  	} else {
>  		ts->sys_monoraw = ktime_sub_ns(ts->sys_monoraw, corr_raw);
>  		ts->sys_systime = ktime_sub_ns(ts->sys_systime, corr_sys);
> @@ -1521,12 +1539,12 @@ int get_device_system_crosststamp(int (*get_time_fn)
>  	case CLOCK_AUX ... CLOCK_AUX_LAST:
>  		tkd = aux_get_tk_data(xtstamp->clock_id);
>  		if (!tkd)
> -			return false;
> +			return -ENODEV;
>  		offs = &tkd->timekeeper.offs_aux;
>  		break;
>  	default:
>  		WARN_ON_ONCE(1);
> -		return false;
> +		return -ENODEV;
>  	}
>  
>  	tk = &tkd->timekeeper;