linux-kernel - Re: [PATCH][RFT] PCI: Use pci_update_current_state() in pci_enable_device

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Date:   Mon, 12 Jul 2021 17:30:04 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Michael <phyre@...ers.com>
Cc:     Maximilian Luz <luzmaximilian@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PCI <linux-pci@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: Re: [PATCH][RFT] PCI: Use pci_update_current_state() in pci_enable_device_flags()

On Fri, Jul 9, 2021 at 1:21 PM Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Thu, Jul 8, 2021 at 10:34 PM Maximilian Luz <luzmaximilian@...il.com> wrote:
> >
> > On 7/8/21 3:25 PM, Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > >
> > > Updating the current_state field of struct pci_dev the way it is done
> > > in pci_enable_device_flags() before calling do_pci_enable_device() may
> > > not work.  For example, if the given PCI device depends on an ACPI
> > > power resource whose _STA method initially returns 0 ("off"), but the
> > > config space of the PCI device is accessible and the power state
> > > retrieved from the PCI_PM_CTRL register is D0, the current_state
> > > field in the struct pci_dev representing that device will get out of
> > > sync with the power.state of its ACPI companion object and that will
> > > lead to power management issues going forward.
> > >
> > > To avoid such issues, make pci_enable_device_flags() call
> > > pci_update_current_state() which takes ACPI device power management
> > > into account, if present, to retrieve the current power state of the
> > > device.
> > >
> > > Link: https://lore.kernel.org/lkml/20210314000439.3138941-1-luzmaximilian@gmail.com/
> > > Reported-by: Maximilian Luz <luzmaximilian@...il.com>
> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > ---
> > >
> > > Hi Maximilian,
> > >
> > > Because commit 4514d991d992 ("PCI: PM: Do not read power state in
> > > pci_enable_device_flags()"), the issue addressed by it is back, so
> > > we need an alternative way to address it.
> > >
> > > Can you please check if this patch makes that issue go away?
> >
> > Hi,
> >
> > just tested this on v5.13 and it works, thanks! Feel free to add
> >
> > Tested-by: Maximilian Luz <luzmaximilian@...il.com>

Michael, Salvatore, since this alternative to commit 4514d991d992
works for Maximilian, I'm going to queue it up for 5.15 (barring any
objections from Bjorn), so I would appreciate it if you could test it
and let me know whether or not there were any problems with it.

The patch can be downloaded from
https://patchwork.kernel.org/project/linux-pm/patch/4327888.LvFx2qVVIh@kreacher

Thanks!