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

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Date:   Wed, 31 Jul 2019 16:19:56 -0600
From:   Keith Busch <kbusch@...nel.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Mario Limonciello <Mario.Limonciello@...l.com>,
        Kai-Heng Feng <kai.heng.feng@...onical.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

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, in which
case we do need to reintroduce the HMB handling.