arm64: add hw_nmi_get_sample_period for preparation of lockup detector

Set safe maximum CPU frequency to 5 GHz in case a particular platform doesn't implement cpufreq driver. Although, architecture doesn't put any restrictions on maximum frequency but 5 GHz seems to be safe maximum given the available Arm CPUs in the market which are clocked much less than 5 GHz. On the other hand, we can't make it much higher as it would lead to a large hard-lockup detection timeout on parts which are running slower (eg. 1GHz on Developerbox) and doesn't possess a cpufreq driver.

Lecopzer Chen committed 3 years ago

Commit 94946f91 parent 930d8f82 files · +25 −0Browse files

Unified · Split

2 files

arch/arm64/kernel/Makefile +1 −0
arch/arm64/kernel/watchdog_hld.c +24 −0

arch/arm64/kernel/Makefile+1−0

@@ -45,6 +45,7 @@ obj-$(CONFIG_FUNCTION_TRACER) += ftrace.o entry-ftrace.o · 44 unmodified lines
45	45	obj-$(CONFIG_MODULES) += module.o
46	46	obj-$(CONFIG_ARM64_MODULE_PLTS) += module-plts.o
47	47	obj-$(CONFIG_PERF_EVENTS) += perf_regs.o perf_callchain.o
	48	+obj-$(CONFIG_HARDLOCKUP_DETECTOR_PERF) += watchdog_hld.o
48	49	obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
49	50	obj-$(CONFIG_CPU_PM) += sleep.o suspend.o
50	51	obj-$(CONFIG_CPU_IDLE) += cpuidle.o

arch/arm64/kernel/watchdog_hld.c+24−0

@@ -0,0 +1,24 @@
	1	+// SPDX-License-Identifier: GPL-2.0
	2	+#include <linux/cpufreq.h>
	3	+
	4	+/*
	5	+ * Safe maximum CPU frequency in case a particular platform doesn't implement
	6	+ * cpufreq driver. Although, architecture doesn't put any restrictions on
	7	+ * maximum frequency but 5 GHz seems to be safe maximum given the available
	8	+ * Arm CPUs in the market which are clocked much less than 5 GHz. On the other
	9	+ * hand, we can't make it much higher as it would lead to a large hard-lockup
	10	+ * detection timeout on parts which are running slower (eg. 1GHz on
	11	+ * Developerbox) and doesn't possess a cpufreq driver.
	12	+ */
	13	+#define SAFE_MAX_CPU_FREQ 5000000000UL // 5 GHz
	14	+u64 hw_nmi_get_sample_period(int watchdog_thresh)
	15	+{
	16	+ unsigned int cpu = smp_processor_id();
	17	+ unsigned long max_cpu_freq;
	18	+
	19	+ max_cpu_freq = cpufreq_get_hw_max_freq(cpu) * 1000UL;
	20	+ if (!max_cpu_freq)
	21	+ max_cpu_freq = SAFE_MAX_CPU_FREQ;
	22	+
	23	+ return (u64)max_cpu_freq * watchdog_thresh;
	24	+}