[Intel-wired-lan] Deep package C-states cannot be reached on e1000e after resume from suspend

[Vitaly Lifshits]

Hello Yatoslav,

On 8/5/2020 03:42, Yaroslav Isakov wrote:
> Hello! I've found that my laptop (T460s) cannot reach Package C-states
> deeper than PC2. After some research, I've found that unplugging cable
> from my laptop and plugging it back fixes that, until the laptop is
> suspended. After resume, this problem returns, but unplugging and
> plugging fix it again.
> I'm using kernel 5.8.0, but I've seen the same behavior on previous
> kernel as well.
> 
> Here is a lspci -n -vv excerpt:
> 00:1f.6 0200: 8086:156f (rev 21)
>      Subsystem: 17aa:2233
>      Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop-
> ParErr- Stepping- SERR- FastB2B- DisINTx+
>      Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort-
> <TAbort- <MAbort- >SERR- <PERR- INTx-
>      Latency: 0
>      Interrupt: pin A routed to IRQ 129
>      Region 0: Memory at e1100000 (32-bit, non-prefetchable) [size=128K]
>      Capabilities: [c8] Power Management version 3
>          Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA
> PME(D0+,D1-,D2-,D3hot+,D3cold+)
>          Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=1 PME-
>      Capabilities: [d0] MSI: Enable+ Count=1/1 Maskable- 64bit+
>          Address: 00000000fee002f8  Data: 0000
>      Capabilities: [e0] PCI Advanced Features
>          AFCap: TP+ FLR+
>          AFCtrl: FLR-
>          AFStatus: TP-
>      Kernel driver in use: e1000e
>      Kernel modules: e1000e
> 
> /sys/bus/pci/devices/0000:00:1f.6/power/control = on (I've changed it
> to auto, but no change in behavoir)
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> 

In order to be able to reach the lowest power state with connected cable 
you need to set pmc to ignore ltr from the GBE.

You can do it by executing:
echo 3 > /sys/kernel/debug/pmc_core/ltr_ignore