** Information type changed from Proprietary to Public
** Also affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Bionic)
Importance: Undecided
Status: New
** Changed in: linux (Ubuntu Bionic)
Status: New => Triaged
** Changed in: linux (Ubuntu Bionic)
Importance: Undecided => Medium
** Changed in: linux (Ubuntu Bionic)
Assignee: (unassigned) => Canonical Kernel Team (canonical-kernel-team)
** Tags added: kernel
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https://bugs.launchpad.net/bugs/1744638
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 <[email protected]>
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
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