arch/arm64/kernel/watchdog_hld.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/nmi.h>
   3 #include <linux/cpufreq.h>
   4 #include <linux/perf/arm_pmu.h>
   5
   6 /*
   7  * Safe maximum CPU frequency in case a particular platform doesn't implement
   8  * cpufreq driver. Although, architecture doesn't put any restrictions on
   9  * maximum frequency but 5 GHz seems to be safe maximum given the available
  10  * Arm CPUs in the market which are clocked much less than 5 GHz. On the other
  11  * hand, we can't make it much higher as it would lead to a large hard-lockup
  12  * detection timeout on parts which are running slower (eg. 1GHz on
  13  * Developerbox) and doesn't possess a cpufreq driver.
  14  */
  15 #define SAFE_MAX_CPU_FREQ       5000000000UL // 5 GHz
  16 u64 hw_nmi_get_sample_period(int watchdog_thresh)
  17 {
  18         unsigned int cpu = smp_processor_id();
  19         unsigned long max_cpu_freq;
  20
  21         max_cpu_freq = cpufreq_get_hw_max_freq(cpu) * 1000UL;
  22         if (!max_cpu_freq)
  23                 max_cpu_freq = SAFE_MAX_CPU_FREQ;
  24
  25         return (u64)max_cpu_freq * watchdog_thresh;
  26 }
  27
  28 bool __init arch_perf_nmi_is_available(void)
  29 {
  30         /*
  31          * hardlockup_detector_perf_init() will success even if Pseudo-NMI turns off,
  32          * however, the pmu interrupts will act like a normal interrupt instead of
  33          * NMI and the hardlockup detector would be broken.
  34          */
  35         return arm_pmu_irq_is_nmi();
  36 }