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Title: [Bug] [CNL] mei: LTR holds platform at Pkg C2, cannot enter deeper Pkg C states Status in intel: New Status in linux package in Ubuntu: Triaged Status in linux source package in Bionic: Triaged Bug description: Description: Platform: CNL-Y8 LPDDR4 PI (merged rail) RVP with BIOS 108 BIOS configuration: https://wiki.ith.intel.com/pages/viewpage.action?pageId=865050787 At least as far back as the 2017-10-25 Intel Next merge, platform will not go deeper than Pkg C2 when system is idle. Upon further debug, using the pmc_core driver to ignore LTR "6", or bit 6 of LTR_IGN, can allow the system can enter Pkg C8. If I'm not mistaken, according to CSpec bit 6 of LTR_IGN will ignore LTR_ME, which is in the MEI driver's domain. Reproduce by: Boot to text console with latest Intel Next kernel (2017-10-30 as of writing) Run turbostat See residency no deeper than Pkg C2 Expected: At idle, system shows nonzero Pkg C8 residency, or deeper. Actual: At idle, system only shows nonzero Pkg C2 residency. Two work-arounds: echo 6 > /sys/kernel/debug/pmc_core/ltr_ignore Run powertop --auto-tune Criteria for closure: Idle system can enter Pkg C8 (or deeper) without having to explicitly "ignore" LTR 6 or otherwise have to manually enable runtime power management for MEI device(s). Commit ids: Upstream commit, planned to be merged into 4.16 commit cc365dcf0e56271bedf3de95f88922abe248e951 Author: Tomas Winkler <tomas.wink...@intel.com> Date: Tue Jan 2 12:01:41 2018 +0200 mei: me: allow runtime pm for platform with D0i3 Target Kernel: 4.16 Target Release: 18.04 To manage notifications about this bug go to: https://bugs.launchpad.net/intel/+bug/1744638/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
