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

[Rafael J. Wysocki]

On Thu, Aug 1, 2019 at 9:05 PM <Mario.Limonciello@xxxxxxxx> wrote:
>
> > -----Original Message-----
> > From: Rafael J. Wysocki <rafael@xxxxxxxxxx>
> > Sent: Thursday, August 1, 2019 12:30 PM
> > To: Kai-Heng Feng; Keith Busch; Limonciello, Mario
> > Cc: 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]
> >
> > On Thu, Aug 1, 2019 at 11:06 AM Kai-Heng Feng
> > <kai.heng.feng@xxxxxxxxxxxxx> wrote:
> > >
> > > at 06:33, Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
> > >
> > > > On Thu, Aug 1, 2019 at 12:22 AM Keith Busch <kbusch@xxxxxxxxxx> wrote:
> > > >> On Wed, Jul 31, 2019 at 11:25:51PM +0200, Rafael J. Wysocki wrote:
> > > >>> A couple of remarks if you will.
> > > >>>
> > > >>> First, we don't know which case is the majority at this point.  For
> > > >>> now, there is one example of each, but it may very well turn out that
> > > >>> the SK Hynix BC501 above needs to be quirked.
> > > >>>
> > > >>> Second, the reference here really is 5.2, so if there are any systems
> > > >>> that are not better off with 5.3-rc than they were with 5.2, well, we
> > > >>> have not made progress.  However, if there are systems that are worse
> > > >>> off with 5.3, that's bad.  In the face of the latest findings the only
> > > >>> way to avoid that is to be backwards compatible with 5.2 and that's
> > > >>> where my patch is going.  That cannot be achieved by quirking all
> > > >>> cases that are reported as "bad", because there still may be
> > > >>> unreported ones.
> > > >>
> > > >> I have to agree. I think your proposal may allow PCI D3cold,
> > > >
> > > > Yes, it may.
> > >
> > > Somehow the 9380 with Toshiba NVMe never hits SLP_S0 with or without
> > > Rafaelâs patch.
> > > But the ârealâ s2idle power consumption does improve with the patch.
> >
> > Do you mean this patch:
> >
> > https://lore.kernel.org/linux-pm/70D536BE-8DC7-4CA2-84A9-
> > AFB067BA520E@xxxxxxxxxxxxx/T/#m456aa5c69973a3b68f2cdd4713a1ce83be5145
> > 8f
> >
> > or the $subject one without the above?
> >
> > > Can we use a DMI based quirk for this platform? It seems like a platform
> > > specific issue.
> >
> > We seem to see too many "platform-specific issues" here. :-)
> >
> > To me, the status quo (ie. what we have in 5.3-rc2) is not defensible.
> > Something needs to be done to improve the situation.
>
> Rafael, would it be possible to try popping out PC401 from the 9380 and into a 9360 to
> confirm there actually being a platform impact or not?

Not really, sorry.

> I was hoping to have something useful from Hynix by now before responding, but oh well.
>
> In terms of what is the majority, I do know that between folks at Dell, Google, Compal,
> Wistron, Canonical, Micron, Hynix, Toshiba, LiteOn, and Western Digital we tested a wide
> variety of SSDs with this patch series.  I would like to think that they are representative of
> what's being manufactured into machines now.

Well, what about drives already in the field?  My concern is mostly
about those ones.

> Notably the LiteOn CL1 was tested with the HMB flushing support and
> and Hynix PC401 was tested with older firmware though.
>
> >
> > > >
> > > >> In which case we do need to reintroduce the HMB handling.
> > > >
> > > > Right.
> > >
> > > The patch alone doesnât break HMB Toshiba NVMe I tested. But I think itâs
> > > still safer to do proper HMB handling.
> >
> > Well, so can anyone please propose something specific?  Like an
> > alternative patch?
>
> This was proposed a few days ago:
> http://lists.infradead.org/pipermail/linux-nvme/2019-July/026056.html
>
> However we're still not sure why it is needed, and it will take some time to get
> a proper failure analysis from LiteOn  regarding the CL1.

Thanks for the update, but IMO we still need to do something before
final 5.3 while the investigation continues.

Honestly, at this point I would vote for going back to the 5.2
behavior at least by default and only running the new code on the
drives known to require it (because they will block PC10 otherwise).

Possibly (ideally) with an option for users who can't get beyond PC3
to test whether or not the new code helps them.