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From:   <Mario.Limonciello@dell.com>
To:     <kbusch@kernel.org>
CC:     <keith.busch@intel.com>, <hch@lst.de>, <sagi@grimberg.me>,
        <linux-nvme@lists.infradead.org>, <rafael@kernel.org>,
        <linux-kernel@vger.kernel.org>, <linux-pm@vger.kernel.org>,
        <kai.heng.feng@canonical.com>
Subject: RE: [PATCH] nvme/pci: Use host managed power state for suspend
Thread-Topic: [PATCH] nvme/pci: Use host managed power state for suspend
Thread-Index: AQHVB3g9crBQ5iluoUuygL0xp1WIm6ZlFnpAgAQIfyCAAFjOAP//rwFA
Date:   Mon, 13 May 2019 14:54:49 +0000
Message-ID: <7ab8274ef1ce46fcae54a50abc76ae4a@AUSX13MPC105.AMER.DELL.COM>
References: <20190510212937.11661-1-keith.busch@intel.com>
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> -----Original Message-----
> From: Keith Busch <kbusch@kernel.org>
> Sent: Monday, May 13, 2019 9:38 AM
> To: Limonciello, Mario
> Cc: keith.busch@intel.com; hch@lst.de; sagi@grimberg.me; linux-
> nvme@lists.infradead.org; rafael@kernel.org; linux-kernel@vger.kernel.org=
; linux-
> pm@vger.kernel.org; kai.heng.feng@canonical.com
> Subject: Re: [PATCH] nvme/pci: Use host managed power state for suspend
>=20
>=20
> [EXTERNAL EMAIL]
>=20
> On Mon, May 13, 2019 at 02:24:41PM +0000, Mario.Limonciello@dell.com wrot=
e:
> > This was not a disk with HMB, but with regard to the HMB I believe it n=
eeds to be
> > removed during s0ix so that there isn't any mistake that SSD thinks it =
can access
> HMB
> > memory in s0ix.
>=20
> Is that really the case, though? Where may I find that DMA is not
> allowed in this state? I just want an authoritative reference to attach
> to the behavior.

The Intel DMA controller suspend callbacks in drivers/dma/idma64.c look to =
me to
turn off the controller.

And NVME spec made it sound to me that while in a low power state it should=
n't
be available if the memory isn't available.

NVME spec in 8.9:

"Host software should request that the controller release the
assigned ranges prior to a shutdown event, a Runtime D3 event, or any other=
 event
that requires host software to reclaim the assigned ranges."