linux-kernel - Re: Query related to shutting down NVMe during system suspend

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Message-ID: <2616042.mvXUDI8C0e@kreacher>
Date:   Tue, 01 Feb 2022 18:17:09 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Vidya Sagar <vidyas@...dia.com>, Keith Busch <kbusch@...nel.org>
Cc:     rafael.j.wysocki@...el.com, keith.busch@...el.com, hch@....de,
        bhelgaas@...gle.com, mmaddireddy@...dia.com, kthota@...dia.com,
        sagar.tv@...il.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: Query related to shutting down NVMe during system suspend

On Tuesday, February 1, 2022 5:30:54 PM CET Keith Busch wrote:
> On Tue, Feb 01, 2022 at 09:52:28PM +0530, Vidya Sagar wrote:
> > Hi Rafael & Christoph,
> > My query is regarding the comment and the code that follows after it at
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/nvme/host/pci.c?h=v5.17-rc2#n3243
> > What I understood from it is that, there is an underlying assumption
> > that the power to the devices is not removed during the suspend call.
> > In the case of device-tree based platforms like Tegra194, power is
> > indeed removed to the devices during suspend-resume process. Hence, the
> > NVMe devices need to be taken through the shutdown path irrespective of
> > whether the ASPM states are enabled or not.
> > I would like to hear from you the best method to follow to achieve this.
> 
> Since platform makers can't converge on how to let a driver know what
> it's supposed to do, I suggest we default to the simple shutdown suspend
> all the time. We can add a module parameter to let a user request nvme
> power management if they really want it. No matter what we do here,
> someone is going to complain, but at least simple shutdown is safe...

Agreed.