linux-kernel - Re: [PATCH 2/2] PCI: Disable Precision Time Measurement during suspend

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Date:   Thu, 19 Nov 2020 11:38:46 -0800
From:   "David E. Box" <david.e.box@...ux.intel.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Len Brown <len.brown@...el.com>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] PCI: Disable Precision Time Measurement during
 suspend

On Thu, 2020-11-19 at 19:13 +0100, Rafael J. Wysocki wrote:
> On Thu, Nov 19, 2020 at 6:45 PM David E. Box
> <david.e.box@...ux.intel.com> wrote:
> > On Thu, 2020-11-19 at 13:01 +0100, Rafael J. Wysocki wrote:
> > > On Thu, Nov 19, 2020 at 1:17 AM David E. Box
> > > <david.e.box@...ux.intel.com> wrote:

...

> > > > 
> > > > +        */
> > > > +       if (pm_suspend_target_state == PM_SUSPEND_TO_IDLE &&
> > > 
> > > AFAICS the target sleep state doesn't matter here, so I'd skip
> > > the
> > > check above, but otherwise it LGTM.
> > 
> > The target sleep state doesn't matter so much but that it's
> > suspending
> > does. pci_save_state() is called during probe for the root ports
> > (and
> > many other pci devices - I'm curious as to why).
> 
> I tend to forget about this, sorry.
> 
> > So without this check the capability gets disabled on boot.
> > 
> 
> So instead of calling this from here, why don't we invoke the code
> below from pci_prepare_to_sleep() and pci_finish_runtime_suspend(),
> before enabling wakeup (and it needs to be re-done on failures, eg.
> by
> restoring the cap from the saved copy)?

Ok.