[PATCH] nvme-pci: Avoid to go into d3cold if device can't use npss.

[Christoph Hellwig]

On Wed, May 26, 2021 at 10:21:59PM +0800, Kai-Heng Feng wrote:
> To be fair, resuming the NVMe from D3hot is much slower than keep it
> at D0, which gives us a faster s2idle resume time. And now AMD also
> requires s2idle on their latest laptops.

We'd much prefer to use it, but due to the broken platforms we can't
unfortunately.

> And it's more like NVMe controllers don't respect PCI D3hot.

What do you mean with that?

> Because the NVMe continues to work after s2idle and the symbol is
> rather subtle, so I suspect this is not platform or vendor specific.
> Is it possible to disable DMA for HMB NVMe on suspend?

Not in shipping products.  The NVMe technical working group is working
on a way to do that, but it will take a while until that shows up in
products.