linux-kernel - Re: [PATCH] nvme-pci: Shutdown the device if D3Cold is allowed by the user

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Message-ID: <CAJZ5v0jfaNjgjNAQPa3QPNdU8BCoocsbo4Vfo5obTxcyTKOUWw@mail.gmail.com>
Date: Mon, 16 Dec 2024 20:43:23 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Keith Busch <kbusch@...nel.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, 
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, Christoph Hellwig <hch@....de>, 
	Ulf Hansson <ulf.hansson@...aro.org>, "Rafael J. Wysocki" <rjw@...ysocki.net>, 
	Bjorn Helgaas <helgaas@...nel.org>, axboe@...nel.dk, sagi@...mberg.me, 
	linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-pci@...r.kernel.org, andersson@...nel.org, konradybcio@...nel.org, 
	Len Brown <len.brown@...el.com>, linux-pm@...r.kernel.org
Subject: Re: [PATCH] nvme-pci: Shutdown the device if D3Cold is allowed by the user

On Mon, Dec 16, 2024 at 8:40 PM Keith Busch <kbusch@...nel.org> wrote:
>
> On Mon, Dec 16, 2024 at 08:34:24PM +0100, Rafael J. Wysocki wrote:
> > However, there is an additional concern that putting an NVMe device
> > into D3cold every time during system suspend on Android might cause it
> > to wear out more quickly.
> >
> > Is there anything else?
>
> I recall a previous reason for this behavior was because the resume
> latency was significantly faster if we don't prepare the device for D3,
> and the nvme protocol specific power states for some platforms was
> sufficiently low enough. Apparently this choice hasn't been universally
> optimal.

Thanks for chiming in!

I'm recalling some other reasons too (mentioned in one of my previous
messages), but overall this is a driver design choice, it is not done
to adhere to some general rule.