Merge tag 'timers-ptp-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull clocksource updates from Thomas Gleixner:
 "Updates for timekeeping and PTP core.

  The cross-timestamp mechanism which allows to correlate hardware
  clocks uses clocksource pointers for describing the correlation.

  That's suboptimal as drivers need to obtain the pointer, which
  requires needless exports and exposing internals. This can all be
  completely avoided by assigning clocksource IDs and using them for
  describing the correlated clock source.

  So this adds clocksource IDs to all clocksources in the tree which can
  be exposed to this mechanism and removes the pointer and now needless
  exports.

  A related improvement for the core and the correlation handling has
  not made it this time, but is expected to get ready for the next
  round"

* tag 'timers-ptp-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  kvmclock: Unexport kvmclock clocksource
  treewide: Remove system_counterval_t.cs, which is never read
  timekeeping: Evaluate system_counterval_t.cs_id instead of .cs
  ptp/kvm, arm_arch_timer: Set system_counterval_t.cs_id to constant
  x86/kvm, ptp/kvm: Add clocksource ID, set system_counterval_t.cs_id
  x86/tsc: Add clocksource ID, set system_counterval_t.cs_id
  timekeeping: Add clocksource ID to struct system_counterval_t
  x86/tsc: Correct kernel-doc notation

3 files changed, 11 insertions, 6 deletions

diff --git a/include/linux/clocksource_ids.h b/include/linux/clocksource_ids.h
index 16775d7d8f8d..a4fa3436940c 100644
--- a/include/linux/clocksource_ids.h
+++ b/include/linux/clocksource_ids.h
@@ -6,6 +6,9 @@
 enum clocksource_ids {
 	CSID_GENERIC		= 0,
 	CSID_ARM_ARCH_COUNTER,
+	CSID_X86_TSC_EARLY,
+	CSID_X86_TSC,
+	CSID_X86_KVM_CLK,
 	CSID_MAX,
 };
 
diff --git a/include/linux/ptp_kvm.h b/include/linux/ptp_kvm.h
index 746fd67c3480..e8c74fa3f455 100644
--- a/include/linux/ptp_kvm.h
+++ b/include/linux/ptp_kvm.h
@@ -8,15 +8,15 @@
 #ifndef _PTP_KVM_H_
 #define _PTP_KVM_H_
 
+#include <linux/clocksource_ids.h>
 #include <linux/types.h>
 
 struct timespec64;
-struct clocksource;
 
 int kvm_arch_ptp_init(void);
 void kvm_arch_ptp_exit(void);
 int kvm_arch_ptp_get_clock(struct timespec64 *ts);
 int kvm_arch_ptp_get_crosststamp(u64 *cycle,
-		struct timespec64 *tspec, struct clocksource **cs);
+		struct timespec64 *tspec, enum clocksource_ids *cs_id);
 
 #endif /* _PTP_KVM_H_ */
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index 7c43e98cf211..7e50cbd97f86 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -268,15 +268,17 @@ 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. Used by
+ *		timekeeping code to verify comparability of two cycle values.
+ *		The default ID, CSID_GENERIC, does not identify a specific
+ *		clocksource.
  */
 struct system_counterval_t {
 	u64			cycles;
-	struct clocksource	*cs;
+	enum clocksource_ids	cs_id;
 };
 
 /*