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

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Message-ID: <20220201163054.GA2838889@dhcp-10-100-145-180.wdc.com>
Date:   Tue, 1 Feb 2022 08:30:54 -0800
From:   Keith Busch <kbusch@...nel.org>
To:     Vidya Sagar <vidyas@...dia.com>
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 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...