From mboxrd@z Thu Jan  1 00:00:00 1970
From: hch@lst.de (Christoph Hellwig)
Date: Mon, 13 May 2019 16:54:15 +0200
Subject: [PATCH] nvme/pci: Use host managed power state for suspend
In-Reply-To: <b12ff66f8c224e4199ff1b90ed6bc393@AUSX13MPC105.AMER.DELL.COM>
References: <20190510212937.11661-1-keith.busch@intel.com>
 <0080aaff18e5445dabca509d4113eca8@AUSX13MPC105.AMER.DELL.COM>
 <955722d8fc16425dbba0698c4806f8fd@AUSX13MPC105.AMER.DELL.COM>
 <20190513143741.GA25500@lst.de>
 <b12ff66f8c224e4199ff1b90ed6bc393@AUSX13MPC105.AMER.DELL.COM>
Message-ID: <20190513145415.GA25774@lst.de>

On Mon, May 13, 2019@02:43:43PM +0000, Mario.Limonciello@dell.com wrote:
> Well I've got a thought, quoting the NVME spec:
> "After a successful completion of a Set Features command for this feature, the controller shall be in the
> Power State specified. If enabled, autonomous power state transitions continue to occur from the new state."
> 
> If APST is enabled on this disk, what is to stop an autonomous  reverse
> transition from queue activity on the way down?

Nothing.  But once the system is suspending we should not see I/O.

If we see I/O the queue freezing in the original patch Kai Heng and the
previous one from Keith is probably required, although I suspect it
just papers over problems higher up in the queue.  If we don't see I/O
the device is just behaving oddly.