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Message-ID: <175129591680.406.14184432653481182434.tip-bot2@tip-bot2>
Date: Mon, 30 Jun 2025 15:05:16 -0000
From: "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>, John Stultz <jstultz@...gle.com>,
x86@...nel.org, linux-kernel@...r.kernel.org
Subject:
[tip: timers/ptp] timekeeping: Provide interface to control auxiliary clocks
The following commit has been merged into the timers/ptp branch of tip:
Commit-ID: 7b95663a3d96b39b40f169dba5faef3e20163c5c
Gitweb: https://git.kernel.org/tip/7b95663a3d96b39b40f169dba5faef3e20163c5c
Author: Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Wed, 25 Jun 2025 20:38:49 +02:00
Committer: Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Fri, 27 Jun 2025 20:13:13 +02:00
timekeeping: Provide interface to control auxiliary clocks
Auxiliary clocks are disabled by default and attempts to access them
fail.
Provide an interface to enable/disable them at run-time.
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: John Stultz <jstultz@...gle.com>
Link: https://lore.kernel.org/all/20250625183758.444626478@linutronix.de
---
Documentation/ABI/stable/sysfs-kernel-time-aux-clocks | 5 +-
kernel/time/timekeeping.c | 116 +++++++++-
2 files changed, 121 insertions(+)
create mode 100644 Documentation/ABI/stable/sysfs-kernel-time-aux-clocks
diff --git a/Documentation/ABI/stable/sysfs-kernel-time-aux-clocks b/Documentation/ABI/stable/sysfs-kernel-time-aux-clocks
new file mode 100644
index 0000000..825508f
--- /dev/null
+++ b/Documentation/ABI/stable/sysfs-kernel-time-aux-clocks
@@ -0,0 +1,5 @@
+What: /sys/kernel/time/aux_clocks/<ID>/enable
+Date: May 2025
+Contact: Thomas Gleixner <tglx@...utronix.de>
+Description:
+ Controls the enablement of auxiliary clock timekeepers.
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 568ba1f..6a61887 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -6,6 +6,7 @@
#include <linux/timekeeper_internal.h>
#include <linux/module.h>
#include <linux/interrupt.h>
+#include <linux/kobject.h>
#include <linux/percpu.h>
#include <linux/init.h>
#include <linux/mm.h>
@@ -2916,6 +2917,121 @@ const struct k_clock clock_aux = {
.clock_adj = aux_clock_adj,
};
+static void aux_clock_enable(clockid_t id)
+{
+ struct tk_read_base *tkr_raw = &tk_core.timekeeper.tkr_raw;
+ struct tk_data *aux_tkd = aux_get_tk_data(id);
+ struct timekeeper *aux_tks = &aux_tkd->shadow_timekeeper;
+
+ /* Prevent the core timekeeper from changing. */
+ guard(raw_spinlock_irq)(&tk_core.lock);
+
+ /*
+ * Setup the auxiliary clock assuming that the raw core timekeeper
+ * clock frequency conversion is close enough. Userspace has to
+ * adjust for the deviation via clock_adjtime(2).
+ */
+ guard(raw_spinlock_nested)(&aux_tkd->lock);
+
+ /* Remove leftovers of a previous registration */
+ memset(aux_tks, 0, sizeof(*aux_tks));
+ /* Restore the timekeeper id */
+ aux_tks->id = aux_tkd->timekeeper.id;
+ /* Setup the timekeeper based on the current system clocksource */
+ tk_setup_internals(aux_tks, tkr_raw->clock);
+
+ /* Mark it valid and set it live */
+ aux_tks->clock_valid = true;
+ timekeeping_update_from_shadow(aux_tkd, TK_UPDATE_ALL);
+}
+
+static void aux_clock_disable(clockid_t id)
+{
+ struct tk_data *aux_tkd = aux_get_tk_data(id);
+
+ guard(raw_spinlock_irq)(&aux_tkd->lock);
+ aux_tkd->shadow_timekeeper.clock_valid = false;
+ timekeeping_update_from_shadow(aux_tkd, TK_UPDATE_ALL);
+}
+
+static DEFINE_MUTEX(aux_clock_mutex);
+
+static ssize_t aux_clock_enable_store(struct kobject *kobj, struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ /* Lazy atoi() as name is "0..7" */
+ int id = kobj->name[0] & 0x7;
+ bool enable;
+
+ if (!capable(CAP_SYS_TIME))
+ return -EPERM;
+
+ if (kstrtobool(buf, &enable) < 0)
+ return -EINVAL;
+
+ guard(mutex)(&aux_clock_mutex);
+ if (enable == test_bit(id, &aux_timekeepers))
+ return count;
+
+ if (enable) {
+ aux_clock_enable(CLOCK_AUX + id);
+ set_bit(id, &aux_timekeepers);
+ } else {
+ aux_clock_disable(CLOCK_AUX + id);
+ clear_bit(id, &aux_timekeepers);
+ }
+ return count;
+}
+
+static ssize_t aux_clock_enable_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
+{
+ unsigned long active = READ_ONCE(aux_timekeepers);
+ /* Lazy atoi() as name is "0..7" */
+ int id = kobj->name[0] & 0x7;
+
+ return sysfs_emit(buf, "%d\n", test_bit(id, &active));
+}
+
+static struct kobj_attribute aux_clock_enable_attr = __ATTR_RW(aux_clock_enable);
+
+static struct attribute *aux_clock_enable_attrs[] = {
+ &aux_clock_enable_attr.attr,
+ NULL
+};
+
+static const struct attribute_group aux_clock_enable_attr_group = {
+ .attrs = aux_clock_enable_attrs,
+};
+
+static int __init tk_aux_sysfs_init(void)
+{
+ struct kobject *auxo, *tko = kobject_create_and_add("time", kernel_kobj);
+
+ if (!tko)
+ return -ENOMEM;
+
+ auxo = kobject_create_and_add("aux_clocks", tko);
+ if (!auxo) {
+ kobject_put(tko);
+ return -ENOMEM;
+ }
+
+ for (int i = 0; i <= MAX_AUX_CLOCKS; i++) {
+ char id[2] = { [0] = '0' + i, };
+ struct kobject *clk = kobject_create_and_add(id, auxo);
+
+ if (!clk)
+ return -ENOMEM;
+
+ int ret = sysfs_create_group(clk, &aux_clock_enable_attr_group);
+
+ if (ret)
+ return ret;
+ }
+ return 0;
+}
+late_initcall(tk_aux_sysfs_init);
+
static __init void tk_aux_setup(void)
{
for (int i = TIMEKEEPER_AUX_FIRST; i <= TIMEKEEPER_AUX_LAST; i++)
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