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

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Date:   Thu, 1 Aug 2019 17:05:54 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Keith Busch <kbusch@...nel.org>,
        Mario Limonciello <Mario.Limonciello@...l.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Keith Busch <keith.busch@...el.com>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        linux-nvme <linux-nvme@...ts.infradead.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rajat Jain <rajatja@...gle.com>
Subject: Re: [Regression] Commit "nvme/pci: Use host managed power state for
 suspend" has problems

at 06:33, Rafael J. Wysocki <rafael@...nel.org> wrote:

> On Thu, Aug 1, 2019 at 12:22 AM Keith Busch <kbusch@...nel.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.

Can we use a DMI based quirk for this platform? It seems like a platform  
specific issue.

>
>> 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.

Kai-Heng