4 files changed, 30 insertions, 3 deletions

diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h
index d4ebf5679f1f..0b6e1040f9e7 100644
--- a/arch/arm/include/asm/arch_timer.h
+++ b/arch/arm/include/asm/arch_timer.h
@@ -106,6 +106,7 @@ static inline u32 arch_timer_get_cntkctl(void)
 static inline void arch_timer_set_cntkctl(u32 cntkctl)
 {
 	asm volatile("mcr p15, 0, %0, c14, c1, 0" : : "r" (cntkctl));
+	isb();
 }
 
 #endif
diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
index a652ce0a5cb2..bdedd8f748d1 100644
--- a/arch/arm64/include/asm/arch_timer.h
+++ b/arch/arm64/include/asm/arch_timer.h
@@ -144,6 +144,7 @@ static inline u32 arch_timer_get_cntkctl(void)
 static inline void arch_timer_set_cntkctl(u32 cntkctl)
 {
 	write_sysreg(cntkctl, cntkctl_el1);
+	isb();
 }
 
 static inline u64 arch_counter_get_cntpct(void)
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index fd4b7f684bd0..13e6baa13a89 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -77,6 +77,7 @@ static bool arch_timer_mem_use_virtual;
 static bool arch_counter_suspend_stop;
 static bool vdso_default = true;
 
+static cpumask_t evtstrm_available = CPU_MASK_NONE;
 static bool evtstrm_enable = IS_ENABLED(CONFIG_ARM_ARCH_TIMER_EVTSTREAM);
 
 static int __init early_evtstrm_cfg(char *buf)
@@ -740,6 +741,7 @@ static void arch_timer_evtstrm_enable(int divider)
 #ifdef CONFIG_COMPAT
 	compat_elf_hwcap |= COMPAT_HWCAP_EVTSTRM;
 #endif
+	cpumask_set_cpu(smp_processor_id(), &evtstrm_available);
 }
 
 static void arch_timer_configure_evtstream(void)
@@ -864,6 +866,16 @@ u32 arch_timer_get_rate(void)
 	return arch_timer_rate;
 }
 
+bool arch_timer_evtstrm_available(void)
+{
+	/*
+	 * We might get called from a preemptible context. This is fine
+	 * because availability of the event stream should be always the same
+	 * for a preemptible context and context where we might resume a task.
+	 */
+	return cpumask_test_cpu(raw_smp_processor_id(), &evtstrm_available);
+}
+
 static u64 arch_counter_get_cntvct_mem(void)
 {
 	u32 vct_lo, vct_hi, tmp_hi;
@@ -929,6 +941,8 @@ static int arch_timer_dying_cpu(unsigned int cpu)
 {
 	struct clock_event_device *clk = this_cpu_ptr(arch_timer_evt);
 
+	cpumask_clear_cpu(smp_processor_id(), &evtstrm_available);
+
 	arch_timer_stop(clk);
 	return 0;
 }
@@ -938,10 +952,16 @@ static DEFINE_PER_CPU(unsigned long, saved_cntkctl);
 static int arch_timer_cpu_pm_notify(struct notifier_block *self,
 				    unsigned long action, void *hcpu)
 {
-	if (action == CPU_PM_ENTER)
+	if (action == CPU_PM_ENTER) {
 		__this_cpu_write(saved_cntkctl, arch_timer_get_cntkctl());
-	else if (action == CPU_PM_ENTER_FAILED || action == CPU_PM_EXIT)
+
+		cpumask_clear_cpu(smp_processor_id(), &evtstrm_available);
+	} else if (action == CPU_PM_ENTER_FAILED || action == CPU_PM_EXIT) {
 		arch_timer_set_cntkctl(__this_cpu_read(saved_cntkctl));
+
+		if (elf_hwcap & HWCAP_EVTSTRM)
+			cpumask_set_cpu(smp_processor_id(), &evtstrm_available);
+	}
 	return NOTIFY_OK;
 }
 
@@ -1017,7 +1037,6 @@ static int __init arch_timer_register(void)
 	if (err)
 		goto out_unreg_notify;
 
-
 	/* Register and immediately configure the timer on the boot CPU */
 	err = cpuhp_setup_state(CPUHP_AP_ARM_ARCH_TIMER_STARTING,
 				"clockevents/arm/arch_timer:starting",
diff --git a/include/clocksource/arm_arch_timer.h b/include/clocksource/arm_arch_timer.h
index cc805b72994a..4e28283e2ec6 100644
--- a/include/clocksource/arm_arch_timer.h
+++ b/include/clocksource/arm_arch_timer.h
@@ -93,6 +93,7 @@ struct arch_timer_mem {
 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);
 
 #else
 
@@ -106,6 +107,11 @@ static inline u64 arch_timer_read_counter(void)
 	return 0;
 }
 
+static inline bool arch_timer_evtstrm_available(void)
+{
+	return false;
+}
+
 #endif
 
 #endif