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Date:   Wed, 9 Feb 2022 12:26:39 -0800
From:   Keith Busch <kbusch@kernel.org>
To:     Vidya Sagar <vidyas@nvidia.com>
Cc:     rafael.j.wysocki@intel.com, keith.busch@intel.com, hch@lst.de,
        bhelgaas@google.com, mmaddireddy@nvidia.com, kthota@nvidia.com,
        sagar.tv@gmail.com, linux-pci@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: Query related to shutting down NVMe during system suspend
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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.

Christoph prefers to append quirks for platforms that need full device
shutdown on s2idle instead of changing the driver default.

We use dmi matching for our current platform quirk list. I do not know
what the equivalent is for device-tree based platforms. Do you know?