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

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Message-ID: <0bd9fdc1-99d4-1c59-7343-3708b331b2b5@nvidia.com>
Date:   Tue, 1 Feb 2022 22:28:44 +0530
From:   Vidya Sagar <vidyas@...dia.com>
To:     Keith Busch <kbusch@...nel.org>
CC:     <rafael.j.wysocki@...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

Thanks for the super quick reply and I couldn't agree more.

On 2/1/2022 10:00 PM, Keith Busch wrote:
> External email: Use caution opening links or attachments
> 
> 
> 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...
>