From: Lecopzer Chen <lecopzer.chen@xxxxxxxxxxxx> 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. Co-developed-by: Sumit Garg <sumit.garg@xxxxxxxxxx> Signed-off-by: Sumit Garg <sumit.garg@xxxxxxxxxx> Co-developed-by: Pingfan Liu <kernelfans@xxxxxxxxx> Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx> Signed-off-by: Lecopzer Chen <lecopzer.chen@xxxxxxxxxxxx> Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx> --- I yanked this patch from the mailing lists [1] into my series just to make it easier to avoid conflicts between my series and the one adding the arm64 perf hardlockup detector, in case someone wanted to test them both together. The only change I made here was to remove an extra blank line that checkpatch complained about. As mentioned in the cover letter, I'm not really expecting this patch to land together with the patches for the buddy detector. I included it with my series simply for convenience of testing both series together. NOTE: the previous patch posted by Lecopzer pointed to Sumit's patch [2] in the commit text but provided no context. I moved it to this "after the cut" note. [1] https://lore.kernel.org/r/20220903093415.15850-6-lecopzer.chen@xxxxxxxxxxxx/ [2] http://lore.kernel.org/linux-arm-kernel/1610712101-14929-1-git-send-email-sumit.garg@xxxxxxxxxx Changes in v4: - Pulled ("add hw_nmi_get_sample_period for ...") into my series for v4. arch/arm64/kernel/Makefile | 1 + arch/arm64/kernel/watchdog_hld.c | 24 ++++++++++++++++++++++++ 2 files changed, 25 insertions(+) create mode 100644 arch/arm64/kernel/watchdog_hld.c diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index ceba6792f5b3..f8e2645406a4 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -46,6 +46,7 @@ obj-$(CONFIG_MODULES) += module.o obj-$(CONFIG_ARM64_MODULE_PLTS) += module-plts.o obj-$(CONFIG_PERF_EVENTS) += perf_regs.o perf_callchain.o obj-$(CONFIG_HW_PERF_EVENTS) += perf_event.o +obj-$(CONFIG_HARDLOCKUP_DETECTOR_PERF) += watchdog_hld.o obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o obj-$(CONFIG_CPU_PM) += sleep.o suspend.o obj-$(CONFIG_CPU_IDLE) += cpuidle.o diff --git a/arch/arm64/kernel/watchdog_hld.c b/arch/arm64/kernel/watchdog_hld.c new file mode 100644 index 000000000000..2401eb1b7e55 --- /dev/null +++ b/arch/arm64/kernel/watchdog_hld.c @@ -0,0 +1,24 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <linux/cpufreq.h> + +/* + * Safe maximum CPU frequency 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. + */ +#define SAFE_MAX_CPU_FREQ 5000000000UL // 5 GHz +u64 hw_nmi_get_sample_period(int watchdog_thresh) +{ + unsigned int cpu = smp_processor_id(); + unsigned long max_cpu_freq; + + max_cpu_freq = cpufreq_get_hw_max_freq(cpu) * 1000UL; + if (!max_cpu_freq) + max_cpu_freq = SAFE_MAX_CPU_FREQ; + + return (u64)max_cpu_freq * watchdog_thresh; +} -- 2.40.1.521.gf1e218fcd8-goog
