Hi. I hope this is the right forum to raise this... For a while I have noticed that my CPU (i9-9880H in a Lenovo X1 Extreme Gen2) never enters any sleep mode below pc2. (Confirmed with powertop and /sys/kernel/debug/pmc_core/package_cstate_show) Interestingly the CPU *can* reachers deeper C states *after* a resume from sleep (either S0ix or S3, i.e. freeze or mem). This article finally pointed me in the right direction: https://01.org/blogs/qwang59/2020/linux-s0ix-troubleshooting Somehow SOUTHPORT_A is requesting a max latency of 1 us. There are no external devices attached. This is before a resume: $ cat /sys/kernel/debug/pmc_core/ltr_show SOUTHPORT_A LTR: RAW: 0x88018c01 Non-Snoop(ns): 1024 Snoop(ns): 32768 <------- SOUTHPORT_B LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 SATA LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 GIGABIT_ETHERNET LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 XHCI LTR: RAW: 0x13ff Non-Snoop(ns): 0 Snoop(ns): 0 Reserved LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 ME LTR: RAW: 0x8000800 Non-Snoop(ns): 0 Snoop(ns): 0 EVA LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 SOUTHPORT_C LTR: RAW: 0x9f409f4 Non-Snoop(ns): 0 Snoop(ns): 0 HD_AUDIO LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 CNV LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 LPSS LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 SOUTHPORT_D LTR: RAW: 0x8c548c54 Non-Snoop(ns): 2752512 Snoop(ns): 2752512 SOUTHPORT_E LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 CAMERA LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 ESPI LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 SCC LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 ISH LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 UFSX2 LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 EMMC LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 WIGIG LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 CURRENT_PLATFORM LTR: RAW: 0x40201 Non-Snoop(ns): 0 Snoop(ns): 0 AGGREGATED_SYSTEM LTR: RAW: 0x7fbfdfe Non-Snoop(ns): 0 Snoop(ns): 0 Notice the 1000ns max latency requirement for SOUTHPORT_A. Ignoring SOUTHPORT_A via /sys/kernel/debug/pmc_core/ltr_ignore subsequently allows the CPU to reach deep sleep states. After a resume it looks like suddenly SOUTHPORT_C is active and with a less tight latency requirement: $ cat /sys/kernel/debug/pmc_core/ltr_show SOUTHPORT_A LTR: RAW: 0x8010c01 Non-Snoop(ns): 0 Snoop(ns): 0 <-------- SOUTHPORT_B LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 SATA LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 GIGABIT_ETHERNET LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 XHCI LTR: RAW: 0x13ff Non-Snoop(ns): 0 Snoop(ns): 0 Reserved LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 ME LTR: RAW: 0x8000800 Non-Snoop(ns): 0 Snoop(ns): 0 EVA LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 SOUTHPORT_C LTR: RAW: 0x88468846 Non-Snoop(ns): 71680 Snoop(ns): 71680 <--------- HD_AUDIO LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 CNV LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 LPSS LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 SOUTHPORT_D LTR: RAW: 0x8c548c54 Non-Snoop(ns): 2752512 Snoop(ns): 2752512 SOUTHPORT_E LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 CAMERA LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 ESPI LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 SCC LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 ISH LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 UFSX2 LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 EMMC LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 WIGIG LTR: RAW: 0x0 Non-Snoop(ns): 0 Snoop(ns): 0 CURRENT_PLATFORM LTR: RAW: 0x40201 Non-Snoop(ns): 0 Snoop(ns): 0 AGGREGATED_SYSTEM LTR: RAW: 0x904824 Non-Snoop(ns): 0 Snoop(ns): 0 Does anybody know what's going on or how to debug this further? As stated above, I was able to work around this problem by ignoring SOUTHPORT_A via /sys/kernel/debug/pmc_core/ltr_ignore. There has to be a better way, and I'm sure I'm not the only one running into this. Thanks. -- Lars
