RE: [PATCH] nvme/pci: Use host managed power state for suspend

[Mario.Limonciello]

> -----Original Message-----
> From: Keith Busch <kbusch@xxxxxxxxxx>
> Sent: Monday, May 13, 2019 9:38 AM
> To: Limonciello, Mario
> Cc: keith.busch@xxxxxxxxx; hch@xxxxxx; sagi@xxxxxxxxxxx; linux-
> nvme@xxxxxxxxxxxxxxxxxxx; rafael@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-
> pm@xxxxxxxxxxxxxxx; kai.heng.feng@xxxxxxxxxxxxx
> Subject: Re: [PATCH] nvme/pci: Use host managed power state for suspend
> 
> 
> [EXTERNAL EMAIL]
> 
> On Mon, May 13, 2019 at 02:24:41PM +0000, Mario.Limonciello@xxxxxxxx wrote:
> > This was not a disk with HMB, but with regard to the HMB I believe it needs to be
> > removed during s0ix so that there isn't any mistake that SSD thinks it can access
> HMB
> > memory in s0ix.
> 
> 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 shouldn'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."