@@ -267,13 +267,13 @@ struct system_device_crosststamp {
};
/**
- * struct system_counterval_t - system counter value with the pointer to the
+ * struct system_counterval_t - system counter value with the ID of the
* corresponding clocksource
* @cycles: System counter value
- * @cs: Clocksource corresponding to system counter value. Used by
- * timekeeping code to verify comparibility of two cycle values
- * @cs_id: Clocksource ID corresponding to system counter value. To be
- * used instead of cs in the future.
+ * @cs: Clocksource corresponding to system counter value. Timekeeping
+ * code now evaluates cs_id instead.
+ * @cs_id: Clocksource ID corresponding to system counter value. Used by
+ * timekeeping code to verify comparability of two cycle values.
* The default ID, CSID_GENERIC, does not identify a specific
* clocksource.
*/
@@ -1232,11 +1232,12 @@ int get_device_system_crosststamp(int (*get_time_fn)
return ret;
/*
- * Verify that the clocksource associated with the captured
- * system counter value is the same as the currently installed
- * timekeeper clocksource
+ * Verify that the clocksource ID associated with the captured
+ * system counter value is the same as for the currently
+ * installed timekeeper clocksource
*/
- if (tk->tkr_mono.clock != system_counterval.cs)
+ if (system_counterval.cs_id == CSID_GENERIC ||
+ tk->tkr_mono.clock->id != system_counterval.cs_id)
return -ENODEV;
cycles = system_counterval.cycles;
Clocksource pointers can be problematic to obtain for drivers which are not clocksource drivers themselves. In particular, the RFC virtio_rtc driver [1] would require a new helper function to obtain a pointer to the Arm Generic Timer clocksource. The ptp_kvm driver also required a similar workaround. Address this by evaluating the clocksource ID, rather than the clocksource pointer, of struct system_counterval_t. By this, setting the clocksource pointer becomes unneeded, and it will be dropped from struct system_counterval_t in the future. By this, get_device_system_crosststamp() callers (such as virtio_rtc and ptp_kvm) will no longer need to supply clocksource pointers. This change should not alter any behavior, as the struct system_counterval_t clocksource ID is already being set wherever the clocksource pointer is set. get_device_system_crosststamp() will now fail if the clocksource has id CSID_GENERIC, but all currently relevant clocksources have a custom clocksource id. [1] https://lore.kernel.org/lkml/20230818012014.212155-1-peter.hilber@opensynergy.com/ Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com> --- Notes: v2: - Refer to clocksource IDs as such in comments (Thomas Gleixner). - Update comments which were still referring to clocksource pointers. include/linux/timekeeping.h | 10 +++++----- kernel/time/timekeeping.c | 9 +++++---- 2 files changed, 10 insertions(+), 9 deletions(-)