[PATCH v3 1/8] clocksource/drivers/arm_arch_timer: Add read_sched_clock_is_arch_counter() predicate

[Marc Zyngier <maz@kernel.org>]

The PMUv3 driver really wants to know whether sched_clock() is
backed by the architected timer. However, updates to the timer driver
have broken the check, as there is more than a single accessor
for the counters, depending on the level of brokenness of the HW.

Add a predicate that checks for those accessors, and update the PMUv3
driver to DTRT.

Fixes: 24ee7607b286b ("arm64/arch_timer: Provide noinstr sched_clock_read() functions")
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
---
 drivers/clocksource/arm_arch_timer.c | 10 ++++++++++
 drivers/perf/arm_pmuv3.c             |  2 +-
 include/clocksource/arm_arch_timer.h |  8 +++++++-
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 4adf756423de9..c02e97f9b7af5 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -951,6 +951,16 @@ static void __init arch_counter_register(void)
 	sched_clock_register(scr, width, arch_timer_rate);
 }
 
+bool read_sched_clock_is_arch_counter(const struct clock_read_data *crd)
+{
+	u64 (*rd)(void) = crd->read_sched_clock;
+
+	return (rd == raw_counter_get_cntvct_stable	||
+		rd == raw_counter_get_cntpct_stable	||
+		rd == arch_counter_get_cntvct		||
+		rd == arch_counter_get_cntpct);
+}
+
 static void arch_timer_stop(struct clock_event_device *clk)
 {
 	pr_debug("disable IRQ%d cpu #%d\n", clk->irq, smp_processor_id());
diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
index 8014ff766cff5..ed880145d41b3 100644
--- a/drivers/perf/arm_pmuv3.c
+++ b/drivers/perf/arm_pmuv3.c
@@ -1624,7 +1624,7 @@ void arch_perf_update_userpage(struct perf_event *event,
 	do {
 		rd = sched_clock_read_begin(&seq);
 
-		if (rd->read_sched_clock != arch_timer_read_counter)
+		if (!read_sched_clock_is_arch_counter(rd))
 			return;
 
 		userpg->time_mult = rd->mult;
diff --git a/include/clocksource/arm_arch_timer.h b/include/clocksource/arm_arch_timer.h
index 2eda895f19f54..84cdbaffcfb5e 100644
--- a/include/clocksource/arm_arch_timer.h
+++ b/include/clocksource/arm_arch_timer.h
@@ -84,13 +84,15 @@ struct arch_timer_mem {
 	struct arch_timer_mem_frame frame[ARCH_TIMER_MEM_MAX_FRAMES];
 };
 
+struct clock_read_data;
+
 #ifdef CONFIG_ARM_ARCH_TIMER
 
 extern u32 arch_timer_get_rate(void);
 extern u64 (*arch_timer_read_counter)(void);
 extern struct arch_timer_kvm_info *arch_timer_get_kvm_info(void);
 extern bool arch_timer_evtstrm_available(void);
-
+extern bool read_sched_clock_is_arch_counter(const struct clock_read_data *);
 #else
 
 static inline u32 arch_timer_get_rate(void)
@@ -108,6 +110,10 @@ static inline bool arch_timer_evtstrm_available(void)
 	return false;
 }
 
+static bool read_sched_clock_is_arch_counter(const struct clock_read_data *crd)
+{
+	return false;
+}
 #endif
 
 #endif
-- 
2.47.3