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8aba056a4e
This patch introduces a new debugfs entry to read current Package cstate residency counters. A similar variant of this patch was discussed earlier "https://patchwork.kernel.org/patch/9908563/" but didn't make it into mainline for various reasons. Current version only adds debugfs entry which is quite useful for S0ix debug but excludes the exported API that was there in initial version. Though there are tools like turbostat and socwatch which can also show this info but sometimes its more practical to have it here as it's hard to switch between various tools for S0ix debug when pmc_core driver is the primary debug tool. Internal and external customers have requested for this patch to be included in the PMC driver on many occasions and Google Chrome OS team has already included it in their builds. This becomes handy when requesting logs from external customers who may not always have above mentioned tools in their integrated kernel builds. Package cstate residency MSRs provide useful debug information about system idle states. In idle states system must enter deeper Package cstates. Package cstates depend not only on Core cstates but also on various IP block's power gating status and LTR values. For Intel Core SoCs Package C10 entry is a must for deeper sleep states such as S0ix. "Suspend-to-idle" should ideally take this path: PC0 -> PC10 -> S0ix. For S0ix debug, its logical to check for Package C10 residency first if for some reason system fails to enter S0ix. Please refer to this link for MSR details: https://software.intel.com/sites/default/files/managed/22/0d/335592-sdm-vol-4.pdf Usage: cat /sys/kernel/debug/pmc_core/package_cstate_show Package C2 : 0xec2e21735f Package C3 : 0xc30113ba4 Package C6 : 0x9ef4be15c5 Package C7 : 0x1e011904 Package C8 : 0x3c5653cfe5a Package C9 : 0x0 Package C10 : 0x16fff4289 Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: "David E. Box" <david.e.box@intel.com> Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Cc: Anshuman Gupta <anshuman.gupta@intel.com> Cc: Len Brown <len.brown@intel.com> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-and-tested-by: Anshuman Gupta <anshuman.gupta@intel.com> Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@linux.intel.com> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org> |
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