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Date: Thu, 5 Oct 2017 21:39:07 +0300 From: Andy Shevchenko <andy.shevchenko@...il.com> To: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>, "Zheng, Lv" <lv.zheng@...el.com>, Len Brown <lenb@...nel.org>, "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v2] ACPI / LPIT: Add Low Power Idle Table (LPIT) support On Thu, Oct 5, 2017 at 9:16 PM, Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com> wrote: > Added functionality to read LPIT table, which provides: > > - Sysfs interface to read residency counters via > /sys/devices/system/cpu/cpuidle/low_power_idle_cpu_residency_us > /sys/devices/system/cpu/cpuidle/low_power_idle_system_residency_us > > Here the count "low_power_idle_cpu_residency_us" shows the time spent > by CPU package in low power state. This is read via MSR interface, which > points to MSR for PKG C10. > > Here the count "low_power_idle_system_residency_us" show the count the > system was in low power state. This is read via MMIO interface. This > is mapped to SLP_S0 residency on modern Intel systems. This residency > is achieved only when CPU is in PKG C10 and all functional blocks are > in low power state. > > It is possible that none of the above counters present or anyone of the > counter present or all counters present. > > For example: On my Kabylake system both of the above counters present. > After suspend to idle these counts updated and prints: > 6916179 > 6998564 > > This counter can be read by tools like turbostat to display. Or it can > be used to debug, if modern systems are reaching desired low power state. > > - Provides an interface to read residency counter memory address > This address can be used to get the base address of PMC memory mapped IO. > This is utilized by intel_pmc_core driver to print more debug information. > + switch (residency_info_mem.gaddr.bit_width) { > + case 8: > + count = readb(residency_info_mem.iomem_addr); > + break; > + case 16: > + count = readw(residency_info_mem.iomem_addr); > + break; > + case 32: > + count = readl(residency_info_mem.iomem_addr); > + break; > + case 64: > + count = readq(residency_info_mem.iomem_addr); > + break; > + default: > + return -EINVAL; > + } I saw something very similar already under drivers/acpi. Can we utilize it (split a helper out of it and re-use)? -- With Best Regards, Andy Shevchenko
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