RE: [Regression] Commit "nvme/pci: Use host managed power state for suspend" has problems

[Mario.Limonciello]

> -----Original Message-----
> From: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
> Sent: Thursday, July 25, 2019 1:20 PM
> To: Rafael J. Wysocki
> Cc: Limonciello, Mario; Rafael J. Wysocki; Keith Busch; Christoph Hellwig; Sagi
> Grimberg; linux-nvme; Linux PM; Linux Kernel Mailing List; Rajat Jain
> Subject: Re: [Regression] Commit "nvme/pci: Use host managed power state for
> suspend" has problems
> 
> 
> [EXTERNAL EMAIL]
> 
> at 01:03, Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
> 
> > On Thu, Jul 25, 2019 at 6:24 PM <Mario.Limonciello@xxxxxxxx> wrote:
> >> +Rajat
> >>
> >>> -----Original Message-----
> >>> From: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
> >>> Sent: Thursday, July 25, 2019 9:03 AM
> >>> To: Rafael J. Wysocki
> >>> Cc: Keith Busch; Christoph Hellwig; Sagi Grimberg; linux-
> >>> nvme@xxxxxxxxxxxxxxxxxxx; Limonciello, Mario; Linux PM; LKML
> >>> Subject: Re: [Regression] Commit "nvme/pci: Use host managed power
> >>> state for
> >>> suspend" has problems
> >>>
> >>>
> >>> [EXTERNAL EMAIL]
> >>>
> >>> Hi Rafael,
> >>>
> >>> at 17:51, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
> >>>
> >>>> Hi Keith,
> >>>>
> >>>> Unfortunately,
> >>>>
> >>>> commit d916b1be94b6dc8d293abed2451f3062f6af7551
> >>>> Author: Keith Busch <keith.busch@xxxxxxxxx>
> >>>> Date:   Thu May 23 09:27:35 2019 -0600
> >>>>
> >>>>     nvme-pci: use host managed power state for suspend
> >>>>
> >>>> doesn't universally improve things.  In fact, in some cases it makes
> >>>> things worse.
> >>>>
> >>>> For example, on the Dell XPS13 9380 I have here it prevents the
> >>>> processor
> >>>> package
> >>>> from reaching idle states deeper than PC2 in suspend-to-idle (which, of
> >>>> course, also
> >>>> prevents the SoC from reaching any kind of S0ix).
> >>>>
> >>>> That can be readily explained too.  Namely, with the commit above the
> >>>> NVMe device
> >>>> stays in D0 over suspend/resume, so the root port it is connected to
> >>>> also
> >>>> has to stay in
> >>>> D0 and that "blocks" package C-states deeper than PC2.
> >>>>
> >>>> In order for the root port to be able to go to D3, the device connected
> >>>> to it also needs
> >>>> to go into D3, so it looks like (at least on this particular machine,
> >>>> but
> >>>> maybe in
> >>>> general), both D3 and the NVMe-specific PM are needed.
> >>
> >> Well this is really unfortunate to hear.  I recall that with some disks
> >> we were
> >> seeing problems where NVME specific PM wasn't working when the disk was
> >> in D3.
> >>
> >> On your specific disk, it would be good to know if just removing the
> >> pci_save_state(pdev)
> >> call helps.
> >
> > Yes, it does help.
> >
> >> If so, :
> >> * that might be a better option to add as a parameter.
> >> * maybe we should double check all the disks one more time with that
> >> tweak.
> >
> > At this point it seems so.
> >
> >>>> I'm not sure what to do here, because evidently there are systems where
> >>>> that commit
> >>>> helps.  I was thinking about adding a module option allowing the user to
> >>>> override the
> >>>> default behavior which in turn should be compatible with 5.2 and earlier
> >>>> kernels.
> >>>
> >>> I just briefly tested s2i on XPS 9370, and the power meter shows a
> >>> 0.8~0.9W
> >>> power consumption so at least I donât see the issue on XPS 9370.
> >>
> >> To me that confirms NVME is down, but it still seems higher than I would
> >> have
> >> expected.  We should be more typically in the order of ~0.3W I think.
> 
>  From what Iâve observed, ~0.8W s2idle is already better than Windows (~1W).
> 0.3W is what I see during S5.

Oh thanks for confirming, I'm probably mixing up with another system.

> 
> >
> > It may go to PC10, but not reach S0ix.
> >
> > Anyway, I run the s2idle tests under turbostat which then tells me
> > what has happened more precisely.
> 
> The XPS 9370 at my hand does reach to s0ix during s2idle:
> # cat /sys/kernel/debug/pmc_core/slp_s0_residency_usec
> 15998400
> 
> So I think keep the root port in D0 is not the culprit here.
> Maybe something is wrong on the ASPM settings?
> 
> Kai-Heng

I have a 9380 on hand and I'm also showing slps0 residency with the SSD in it
and this series (Hynix BC501).