linux-kernel - Re: [PATCH] nvme-pci: Use non-operational power state instead of D3 on Suspend-to-Idle

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Date:   Thu, 9 May 2019 15:16:09 -0600
From:   Keith Busch <kbusch@...nel.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Mario Limonciello <Mario.Limonciello@...l.com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Linux PM <linux-pm@...r.kernel.org>,
        Rafael Wysocki <rafael.j.wysocki@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-nvme <linux-nvme@...ts.infradead.org>,
        Keith Busch <keith.busch@...el.com>
Subject: Re: [PATCH] nvme-pci: Use non-operational power state instead of D3
 on Suspend-to-Idle

On Thu, May 09, 2019 at 10:54:04PM +0200, Rafael J. Wysocki wrote:
> On Thu, May 9, 2019 at 9:33 PM Keith Busch <kbusch@...nel.org> wrote:
> >  #include <linux/io-64-nonatomic-lo-hi.h>
> > @@ -2851,6 +2852,8 @@ static int nvme_suspend(struct device *dev)
> >         struct pci_dev *pdev = to_pci_dev(dev);
> >         struct nvme_dev *ndev = pci_get_drvdata(pdev);
> >
> > +       if (!pm_suspend_via_firmware())
> > +               return nvme_set_power(&ndev->ctrl, ndev->ctrl.npss);
> 
> You probably want to call pci_save_state(pdev) in the branch above to
> prevent pci_pm_suspend_noirq() from calling pci_prepare_to_sleep()
> going forward, so I would write this routine as
> 
> if (pm_suspend_via_firmware()) {
>         nvme_dev_disable(ndev, true);
>         return 0;
> }
> 
> pci_save_state(pdev)
> return nvme_set_power(&ndev->ctrl, ndev->ctrl.npss);

Ah, good point. I'll make sure that's added and will wait to see hear if
there's any other feedback.

I am trying to test the paths by faking out PS capabilities, and have
a question on how to force each:

Running "rtcwake -m freeze ...", that takes the !pm_suspend_via_firmware()
path as I expected.

But trying to test the original path, I thought using "-m mem" would
have been a suspend via firmware, but that is still returning false.

Is that expected? I've only tried this on one platform so far, so might
just be this particular one is missing a firmware capability.