[PATCH 2/2] arm64/watchdog_hld: Add a cpufreq notifier for update watchdog thresh

[Yicong Yang]

From: Yicong Yang <yangyicong at hisilicon.com>

arm64 depends on the cpufreq driver to gain the maximum cpu frequency
to convert the watchdog_thresh to perf event period. cpufreq drivers
like cppc_cpufreq will be initialized lately after the initializing of
the hard lockup detector so just use a safe cpufreq which will be
inaccurency. Use a cpufreq notifier to adjust the event's period to
a more accurate one.

Signed-off-by: Yicong Yang <yangyicong at hisilicon.com>
---
 arch/arm64/kernel/watchdog_hld.c | 34 ++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/arch/arm64/kernel/watchdog_hld.c b/arch/arm64/kernel/watchdog_hld.c
index dcd25322127c..719ae39e8bc0 100644
--- a/arch/arm64/kernel/watchdog_hld.c
+++ b/arch/arm64/kernel/watchdog_hld.c
@@ -34,3 +34,37 @@ bool __init arch_perf_nmi_is_available(void)
 	 */
 	return arm_pmu_irq_is_nmi();
 }
+
+static int watchdog_freq_notifier_callback(struct notifier_block *nb,
+					   unsigned long val, void *data)
+{
+	struct cpufreq_policy *policy = data;
+	unsigned long max_cpu_freq;
+	u64 new_period;
+	int cpu;
+
+	if (val != CPUFREQ_CREATE_POLICY)
+		return 0;
+
+	for_each_cpu(cpu, policy->cpus) {
+		max_cpu_freq = cpufreq_get_hw_max_freq(cpu) * 1000UL;
+		if (!max_cpu_freq)
+			continue;
+
+		new_period = watchdog_thresh * max_cpu_freq;
+		hardlockup_detector_perf_adjust_period(cpu, new_period);
+	}
+
+	return 0;
+}
+
+static struct notifier_block watchdog_freq_notifier = {
+	.notifier_call = watchdog_freq_notifier_callback,
+};
+
+static int __init init_watchdog_freq_notifier(void)
+{
+	return cpufreq_register_notifier(&watchdog_freq_notifier,
+					 CPUFREQ_POLICY_NOTIFIER);
+}
+core_initcall(init_watchdog_freq_notifier);
-- 
2.24.0