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

Kai-Heng Feng
2019-08-02T10:56:01Z

at 06:26, Rafael J. Wysocki <rafael@kernel.org> wrote:

> On Thu, Aug 1, 2019 at 9:05 PM <Mario.Limonciello@dell.com> wrote:
>>> -----Original Message-----
>>> From: Rafael J. Wysocki <rafael@kernel.org>
>>> 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@canonical.com> wrote:
>>>> at 06:33, Rafael J. Wysocki <rafael@kernel.org> wrote:
>>>>
>>>>> On Thu, Aug 1, 2019 at 12:22 AM Keith Busch <kbusch@kernel.org> 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
>>>> Rafael’s patch.
>>>> But the “real” s2idle power consumption does improve with the patch.
>>>
>>> Do you mean this patch:
>>>
>>> https://lore.kernel.org/linux-pm/70D536BE-8DC7-4CA2-84A9-
>>> AFB067BA520E@canonical.com/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 doesn’t break HMB Toshiba NVMe I tested. But I think
>>>> it’s
>>>> 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.

I just found out that the XPS 9380 at my hand never reaches SLP_S0 but only
PC10.
This happens with or without putting the device to D3.

Kai-Heng