linux-kernel - Re: [PATCH v5 2/2] PCI/PM: Fix pci_pm_suspend

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Date:   Thu, 12 May 2022 13:35:40 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Rajvi Jingar <rajvi.jingar@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        David Box <david.e.box@...ux.intel.com>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v5 2/2] PCI/PM: Fix pci_pm_suspend_noirq() to disable PTM

On Thu, May 12, 2022 at 07:52:36PM +0200, Rafael J. Wysocki wrote:
> On Thu, May 12, 2022 at 7:42 PM Bjorn Helgaas <helgaas@...nel.org> wrote:
> > On Thu, May 12, 2022 at 03:49:18PM +0200, Rafael J. Wysocki wrote:

> > > Something like this should suffice IMV:
> > >
> > > if (!dev_state_saved || pci_dev->current_state != PCI_D3cold)
> > >
> > >         pci_disable_ptm(pci_dev);
> >
> > It makes sense to me that we needn't disable PTM if the device is in
> > D3cold.  But the "!dev_state_saved" condition depends on what the
> > driver did.  Why is that important?  Why should we not do the
> > following?
> >
> >   if (pci_dev->current_state != PCI_D3cold)
> >     pci_disable_ptm(pci_dev);
> 
> We can do this too.  I thought we could skip the power state check if
> dev_state_saved was unset, because then we would know that the power
> state was not D3cold.  It probably isn't worth the hassle though.

Ah, thanks.  IMHO it's easier to analyze for correctness if we only
check the power state.

Bjorn