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timekeeping: Add system_counterval_t to struct system_device_crosststamp

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An upcoming extension to the PTP IOCTL requires to return the system counter
value and the clocksource ID to user space. get_device_system_crosststamp() has
this information already.

Extend struct system_device_crosststamp with a system_counterval_t member
and fill in the data.

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: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20260529195557.429406675@kernel.org
This commit is contained in:
Thomas Gleixner
2026-05-29 22:00:28 +02:00
parent 23c1bfa9f8
commit 6c14771816
2 changed files with 37 additions and 39 deletions
Download Patch File Download Diff File Expand all files Collapse all files

28
include/linux/timekeeping.h
View File

@@ -296,19 +296,6 @@ struct system_time_snapshot {
u8 valid;
};
/**
* struct system_device_crosststamp - system/device cross-timestamp
* (synchronized capture)
* @device: Device time
* @sys_realtime: Realtime simultaneous with device time
* @sys_monoraw: Monotonic raw simultaneous with device time
*/
struct system_device_crosststamp {
ktime_t device;
ktime_t sys_realtime;
ktime_t sys_monoraw;
};
/**
* struct system_counterval_t - system counter value with the ID of the
* corresponding clocksource
@@ -325,6 +312,21 @@ struct system_counterval_t {
bool use_nsecs;
};
/**
* struct system_device_crosststamp - system/device cross-timestamp
* (synchronized 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 {
ktime_t device;
struct system_counterval_t sys_counter;
ktime_t sys_realtime;
ktime_t sys_monoraw;
};
extern bool ktime_real_to_base_clock(ktime_t treal,
enum clocksource_ids base_id, u64 *cycles);
extern bool timekeeping_clocksource_has_base(enum clocksource_ids id);

48
kernel/time/timekeeping.c
View File

@@ -1418,6 +1418,8 @@ static bool convert_base_to_cs(struct system_counterval_t *scv)
return false;
scv->cycles += base->offset;
/* Set the clocksource ID as scv::cycles is now clocksource based */
scv->cs_id = cs->id;
return true;
}
@@ -1485,11 +1487,11 @@ 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
* system counter from the device driver
* @get_time_fn: Callback to get simultaneous device time and system counter
* from the device driver
* @ctx: Context passed to get_time_fn()
* @history_begin: Historical reference point used to interpolate system
* time when counter provided by the driver is before the current interval
* @history_begin: Historical reference point used to interpolate system time when
* the counter value provided by the driver is before the current interval
* @xtstamp: Receives simultaneously captured system and device time
*
* Reads a timestamp from a device and correlates it to system time
@@ -1502,14 +1504,12 @@ int get_device_system_crosststamp(int (*get_time_fn)
struct system_time_snapshot *history_begin,
struct system_device_crosststamp *xtstamp)
{
struct system_counterval_t system_counterval = {};
u64 syscnt_cycles, cycles, now, interval_start;
struct timekeeper *tk = &tk_core.timekeeper;
u64 cycles, now, interval_start;
unsigned int clock_was_set_seq = 0;
unsigned int seq, clock_was_set_seq = 0;
ktime_t base_real, base_raw;
u64 nsec_real, nsec_raw;
u8 cs_was_changed_seq;
unsigned int seq;
bool do_interp;
int ret;
@@ -1519,19 +1519,20 @@ int get_device_system_crosststamp(int (*get_time_fn)
* Try to synchronously capture device time and a system
* counter value calling back into the device driver
*/
ret = get_time_fn(&xtstamp->device, &system_counterval, ctx);
ret = get_time_fn(&xtstamp->device, &xtstamp->sys_counter, ctx);
if (ret)
return ret;
/*
* Verify that the clocksource ID associated with the captured
* system counter value is the same as for the currently
* installed timekeeper clocksource
* installed timekeeper clocksource and convert to it.
*/
if (system_counterval.cs_id == CSID_GENERIC ||
!convert_base_to_cs(&system_counterval))
if (xtstamp->sys_counter.cs_id == CSID_GENERIC ||
!convert_base_to_cs(&xtstamp->sys_counter))
return -ENODEV;
cycles = system_counterval.cycles;
cycles = syscnt_cycles = xtstamp->sys_counter.cycles;
/*
* Check whether the system counter value provided by the
@@ -1573,24 +1574,19 @@ int get_device_system_crosststamp(int (*get_time_fn)
* clocksource change
*/
if (!history_begin ||
!timestamp_in_interval(history_begin->cycles,
cycles, system_counterval.cycles) ||
!timestamp_in_interval(history_begin->cycles, cycles, syscnt_cycles) ||
history_begin->cs_was_changed_seq != cs_was_changed_seq)
return -EINVAL;
partial_history_cycles = cycles - system_counterval.cycles;
total_history_cycles = cycles - history_begin->cycles;
discontinuity =
history_begin->clock_was_set_seq != clock_was_set_seq;
ret = adjust_historical_crosststamp(history_begin,
partial_history_cycles,
total_history_cycles,
discontinuity, xtstamp);
if (ret)
return ret;
partial_history_cycles = cycles - syscnt_cycles;
total_history_cycles = cycles - history_begin->cycles;
discontinuity = history_begin->clock_was_set_seq != clock_was_set_seq;
ret = adjust_historical_crosststamp(history_begin, partial_history_cycles,
total_history_cycles, discontinuity, xtstamp);
}
return 0;
return ret;
}
EXPORT_SYMBOL_GPL(get_device_system_crosststamp);