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Message-ID: <20250513145138.212062332@linutronix.de>
Date: Tue, 13 May 2025 17:13:44 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: netdev@...r.kernel.org,
Richard Cochran <richardcochran@...il.com>,
Christopher Hall <christopher.s.hall@...el.com>,
David Zage <david.zage@...el.com>,
John Stultz <jstultz@...gle.com>,
Frederic Weisbecker <frederic@...nel.org>,
Anna-Maria Behnsen <anna-maria@...utronix.de>,
Miroslav Lichvar <mlichvar@...hat.com>,
Werner Abt <werner.abt@...nberg-usa.com>,
David Woodhouse <dwmw2@...radead.org>,
Stephen Boyd <sboyd@...nel.org>,
Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
Kurt Kanzenbach <kurt@...utronix.de>,
Nam Cao <namcao@...utronix.de>,
Alex Gieringer <gieri@...utronix.de>
Subject: [patch 26/26] timekeeping: Provide interface to control independent
PTP clocks
Independent PTP 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>
---
Documentation/ABI/stable/sysfs-kernel-time-ptp | 6 +
kernel/time/timekeeping.c | 125 +++++++++++++++++++++++++
2 files changed, 131 insertions(+)
--- /dev/null
+++ b/Documentation/ABI/stable/sysfs-kernel-time-ptp
@@ -0,0 +1,6 @@
+What: /sys/kernel/time/ptp/<ID>/enable
+Date: May 2025
+Contact: Thomas Gleixner <tglx@...utronix.de>
+Description:
+ Controls the enablement of independent PTP clock
+ timekeepers.
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -14,6 +14,7 @@
#include <linux/sched/loadavg.h>
#include <linux/sched/clock.h>
#include <linux/syscore_ops.h>
+#include <linux/sysfs.h>
#include <linux/clocksource.h>
#include <linux/jiffies.h>
#include <linux/time.h>
@@ -2900,6 +2901,130 @@ const struct k_clock clock_ptp = {
.clock_adj = ptp_clock_adj,
};
+static void ptp_clock_enable(unsigned int id)
+{
+ struct tk_read_base *tkr_raw = &tk_core.timekeeper.tkr_raw;
+ struct tk_data *tkd = ptp_get_tk_data(id);
+ struct timekeeper *tks = &tkd->shadow_timekeeper;
+
+ /* Prevent the core timekeeper from changing. */
+ guard(raw_spinlock_irq)(&tk_core.lock);
+
+ /*
+ * Setup the PTP clock assuming that the raw core timekeeper clock
+ * frequency conversion is close enough. PTP userspace has to
+ * adjust for the deviation via clock_adjtime(2).
+ */
+ guard(raw_spinlock_nested)(&tkd->lock);
+
+ /* Remove leftovers of a previous registration */
+ memset(tks, 0, sizeof(*tks));
+ /* Restore the timekeeper id */
+ tks->id = tkd->timekeeper.id;
+ /* Setup the timekeeper based on the current system clocksource */
+ tk_setup_internals(tks, tkr_raw->clock);
+
+ /* Mark it valid and set it live */
+ tks->clock_valid = true;
+ timekeeping_update_from_shadow(tkd, TK_UPDATE_ALL);
+}
+
+static void ptp_clock_disable(unsigned int id)
+{
+ struct tk_data *tkd = ptp_get_tk_data(id);
+
+ guard(raw_spinlock_irq)(&tkd->lock);
+ tkd->shadow_timekeeper.clock_valid = false;
+ timekeeping_update_from_shadow(tkd, TK_UPDATE_ALL);
+}
+
+static DEFINE_MUTEX(ptp_clock_mutex);
+
+static ssize_t ptp_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)(&ptp_clock_mutex);
+ if (enable == test_bit(id, &ptp_timekeepers))
+ return count;
+
+ if (enable) {
+ ptp_clock_enable(CLOCK_PTP + id);
+ set_bit(id, &ptp_timekeepers);
+ } else {
+ ptp_clock_disable(CLOCK_PTP + id);
+ clear_bit(id, &ptp_timekeepers);
+ }
+ return count;
+}
+
+static ssize_t ptp_clock_enable_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
+{
+ unsigned long active = READ_ONCE(ptp_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 ptp_clock_enable_attr = __ATTR_RW(ptp_clock_enable);
+
+static struct attribute *ptp_clock_enable_attrs[] = {
+ &ptp_clock_enable_attr.attr,
+ NULL,
+};
+
+static const struct attribute_group ptp_clock_enable_attr_group = {
+ .attrs = ptp_clock_enable_attrs,
+};
+
+static int __init tk_ptp_sysfs_init(void)
+{
+ struct kobject *ptpo, *tko = kobject_create_and_add("time", kernel_kobj);
+
+ if (!tko) {
+ pr_warn("Unable to create /sys/kernel/time/. POSIX PTP clocks disabled.\n");
+ return -ENOMEM;
+ }
+
+ ptpo = kobject_create_and_add("ptp_clocks", tko);
+ if (!ptpo) {
+ pr_warn("Unable to create /sys/kernel/time/ptp_clocks. POSIX PTP clocks disabled.\n");
+ kobject_put(tko);
+ return -ENOMEM;
+ }
+
+ for (int i = TIMEKEEPER_PTP; i <= TIMEKEEPER_PTP_LAST; i++) {
+ char id[2] = { [0] = '0' + (i - TIMEKEEPER_PTP), };
+ struct kobject *clk = kobject_create_and_add(id, ptpo);
+
+ if (!clk) {
+ pr_warn("Unable to create /sys/kernel/time/ptp_clocks/%d\n",
+ i - TIMEKEEPER_PTP);
+ return -ENOMEM;
+ }
+
+ int ret = sysfs_create_group(clk, &ptp_clock_enable_attr_group);
+
+ if (ret) {
+ pr_warn("Unable to create /sys/kernel/time/ptp_clocks/%d/enable\n",
+ i - TIMEKEEPER_PTP);
+ return ret;
+ }
+ }
+ return 0;
+}
+late_initcall(tk_ptp_sysfs_init);
+
static __init void tk_ptp_setup(void)
{
for (int i = TIMEKEEPER_PTP; i <= TIMEKEEPER_PTP_LAST; i++)
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