linux-kernel - [PATCH v1 3/6] x86/tsc: Check if the current clock source is related to ART(Always Running Timer)

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Message-Id: <20231017052457.25287-4-lakshmi.sowjanya.d@intel.com>
Date:   Tue, 17 Oct 2023 10:54:54 +0530
From:   lakshmi.sowjanya.d@...el.com
To:     tglx@...utronix.de, jstultz@...gle.com, giometti@...eenne.com,
        corbet@....net, linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, linux-doc@...r.kernel.org,
        andriy.shevchenko@...ux.intel.com, eddie.dong@...el.com,
        christopher.s.hall@...el.com, pandith.n@...el.com,
        mallikarjunappa.sangannavar@...el.com, thejesh.reddy.t.r@...el.com,
        lakshmi.sowjanya.d@...el.com
Subject: [PATCH v1 3/6] x86/tsc: Check if the current clock source is related to ART(Always Running Timer)

From: Lakshmi Sowjanya D <lakshmi.sowjanya.d@...el.com>

Add interface 'is_current_clocksource_art_related()' in tsc.c to check
if the current clock source is ART related.
Add helper function 'is_current_clocksource(clock)' in timekeeping.c to
check if the provided clock matches the current clock source.

Co-developed-by: Christopher Hall <christopher.s.hall@...el.com>
Signed-off-by: Christopher Hall <christopher.s.hall@...el.com>
Signed-off-by: Lakshmi Sowjanya D <lakshmi.sowjanya.d@...el.com>
---
 arch/x86/include/asm/tsc.h  |  1 +
 arch/x86/kernel/tsc.c       | 12 ++++++++++++
 include/linux/timekeeping.h |  2 ++
 kernel/time/timekeeping.c   | 15 +++++++++++++++
 4 files changed, 30 insertions(+)

diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index f5cff8d4f61e..cdfe34e55cf3 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -32,6 +32,7 @@ static inline cycles_t get_cycles(void)
 extern int convert_tsc_to_art(const struct system_counterval_t *tsc, u64 *art);
 extern struct system_counterval_t convert_art_to_tsc(u64 art);
 extern struct system_counterval_t convert_art_ns_to_tsc(u64 art_ns);
+extern bool is_current_clocksource_art_related(void);
 
 extern void tsc_early_init(void);
 extern void tsc_init(void);
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 92b800015d8f..2d6b1b5b5b3e 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -16,6 +16,7 @@
 #include <linux/timex.h>
 #include <linux/static_key.h>
 #include <linux/static_call.h>
+#include <linux/timekeeping.h>
 
 #include <asm/hpet.h>
 #include <asm/timer.h>
@@ -1295,6 +1296,17 @@ int unsynchronized_tsc(void)
 	return 0;
 }
 
+/*
+ * Checks if the current clocksource is ART related clocksource
+ *
+ * Return: 1 on success, 0 on failure.
+ */
+bool is_current_clocksource_art_related(void)
+{
+	return is_current_clocksource(art_related_clocksource);
+}
+EXPORT_SYMBOL_GPL(is_current_clocksource_art_related);
+
 /*
  * Converts input TSC to the corresponding ART value using conversion
  * factors discovered by detect_art().
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index e5eb6699d691..9bf7970b3b2f 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -292,6 +292,8 @@ extern int get_device_system_crosststamp(
 extern int ktime_convert_real_to_system_counter(ktime_t sys_realtime,
 						struct system_counterval_t *ret);
 
+extern bool is_current_clocksource(struct clocksource *clock);
+
 /*
  * Simultaneously snapshot realtime and monotonic raw clocks
  */
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index ff6a4c7387ee..986089d36ba5 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1357,6 +1357,21 @@ int ktime_convert_real_to_system_counter(ktime_t sys_realtime,
 }
 EXPORT_SYMBOL_GPL(ktime_convert_real_to_system_counter);
 
+/**
+ * is_current_clocksource - Checks if the supplied clock source matches with the
+ * MONOTONIC clock.
+ *
+ * @clock: pointer to the clocksource to be checked
+ *
+ * Return: true if the clocks match, false otherwise.
+ */
+bool is_current_clocksource(struct clocksource *clock)
+{
+	struct tk_read_base *tkr = &tk_core.timekeeper.tkr_mono;
+	return clock == READ_ONCE(tkr->clock);
+}
+EXPORT_SYMBOL_GPL(is_current_clocksource);
+
 /**
  * do_settimeofday64 - Sets the time of day.
  * @ts:     pointer to the timespec64 variable containing the new time
-- 
2.17.1