From: Jianyong Wu <jianyong.wu@arm.com>
To: netdev@vger.kernel.org, yangbo.lu@nxp.com,
john.stultz@linaro.org, tglx@linutronix.de, pbonzini@redhat.com,
sean.j.christopherson@intel.com, maz@kernel.org,
richardcochran@gmail.com, Mark.Rutland@arm.com,
Will.Deacon@arm.com, suzuki.poulose@arm.com
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Steve.Capper@arm.com, Kaly.Xin@arm.com, justin.he@arm.com,
jianyong.wu@arm.com, nd@arm.com,
linux-arm-kernel@lists.infradead.org
Subject: [RFC PATCH v3 3/6] timekeeping: Expose API allowing retrival of current clocksource and counter value
Date: Wed, 18 Sep 2019 04:07:13 -0400 [thread overview]
Message-ID: <20190918080716.64242-4-jianyong.wu@arm.com> (raw)
In-Reply-To: <20190918080716.64242-1-jianyong.wu@arm.com>
From Marc Zyngier <maz@kernel.org>
A number of PTP drivers (such as ptp-kvm) are assuming what the
current clock source is, which could lead to interesting effects on
systems where the clocksource can change depending on external events.
For this purpose, add a new API that retrives both the current
monotonic clock as well as its counter value.
From Jianyong Wu: export this API then modules can use it.
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
---
include/linux/timekeeping.h | 3 +++
kernel/time/timekeeping.c | 13 +++++++++++++
2 files changed, 16 insertions(+)
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index a8ab0f143ac4..a5389adaa8bc 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -247,6 +247,9 @@ extern int get_device_system_crosststamp(
struct system_time_snapshot *history,
struct system_device_crosststamp *xtstamp);
+/* Obtain current monotonic clock and its counter value */
+extern void get_current_counterval(struct system_counterval_t *sc);
+
/*
* Simultaneously snapshot realtime and monotonic raw clocks
*/
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 44b726bab4bd..07a0969625b1 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1098,6 +1098,19 @@ static bool cycle_between(u64 before, u64 test, u64 after)
return false;
}
+/**
+ * get_current_counterval - Snapshot the current clocksource and counter value
+ * @sc: Pointer to a struct containing the current clocksource and its value
+ */
+void get_current_counterval(struct system_counterval_t *sc)
+{
+ struct timekeeper *tk = &tk_core.timekeeper;
+
+ sc->cs = READ_ONCE(tk->tkr_mono.clock);
+ sc->cycles = sc->cs->read(sc->cs);
+}
+EXPORT_SYMBOL_GPL(get_current_counterval);
+
/**
* get_device_system_crosststamp - Synchronously capture system/device timestamp
* @get_time_fn: Callback to get simultaneous device time and
--
2.17.1
next prev parent reply other threads:[~2019-09-18 8:07 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-18 8:07 [RFC PATCH v3 0/6] Enable ptp_kvm for arm64 Jianyong Wu
2019-09-18 8:07 ` [RFC PATCH v3 1/6] psci: Export psci_ops.conduit symbol as modules will use it Jianyong Wu
2019-09-18 8:07 ` [RFC PATCH v3 2/6] ptp: Reorganize ptp_kvm modules to make it arch-independent Jianyong Wu
2019-09-18 8:07 ` Jianyong Wu [this message]
2019-09-18 8:29 ` [RFC PATCH v3 3/6] timekeeping: Expose API allowing retrival of current clocksource and counter value Paolo Bonzini
2019-09-18 8:07 ` [RFC PATCH v3 4/6] psci: Add hvc call service for ptp_kvm Jianyong Wu
2019-09-18 8:25 ` Paolo Bonzini
2019-09-18 9:57 ` Jianyong Wu (Arm Technology China)
2019-09-18 10:23 ` Paolo Bonzini
2019-09-19 9:46 ` Jianyong Wu (Arm Technology China)
2019-09-19 11:07 ` Paolo Bonzini
2019-09-19 11:39 ` Marc Zyngier
2019-09-19 12:13 ` Paolo Bonzini
2019-09-23 3:19 ` Jianyong Wu (Arm Technology China)
2019-10-09 5:21 ` Jianyong Wu (Arm Technology China)
2019-10-09 6:36 ` Paolo Bonzini
2019-10-09 8:18 ` Jianyong Wu (Arm Technology China)
2019-10-09 9:13 ` Paolo Bonzini
2019-10-09 16:05 ` John Stultz
2019-10-09 20:56 ` Paolo Bonzini
2019-10-14 5:50 ` Jianyong Wu (Arm Technology China)
2019-10-14 6:58 ` Paolo Bonzini
2019-09-23 4:57 ` Jianyong Wu (Arm Technology China)
2019-09-24 14:20 ` Paolo Bonzini
2019-09-25 10:27 ` Jianyong Wu (Arm Technology China)
2019-09-18 8:07 ` [RFC PATCH v3 5/6] ptp: arm64: Enable ptp_kvm for arm64 Jianyong Wu
2019-09-18 8:07 ` [RFC PATCH v3 6/6] kvm: arm64: Add capability check extension for ptp_kvm Jianyong Wu
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