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