linux-kernel - Re: [PATCH 2/2] PCI/PTM: fix in pci_disable

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Date:   Thu, 7 Jul 2022 20:32:13 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Rajvi Jingar <rajvi.jingar@...ux.intel.com>
Cc:     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 2/2] PCI/PTM: fix in pci_disable_ptm()

On Thu, Jul 7, 2022 at 8:27 PM Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Thu, Jul 7, 2022 at 7:22 PM Rajvi Jingar
> <rajvi.jingar@...ux.intel.com> wrote:
> >
> > Set ptm_enabled from 'struct pci_dev' to 0 in pci_ptm_disable() to
>
> I would set "Clear" here instead of "Set", but moreover ->

s/set/say/ sorry.

> > save the disabled PTM state for the device.
> >
> > Fixes: a697f072f5da ("PCI: Disable PTM during suspend to save power")
> > Signed-off-by: Rajvi Jingar <rajvi.jingar@...ux.intel.com>
> > ---
> >  drivers/pci/pcie/ptm.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c
> > index 368a254e3124..746e29779c27 100644
> > --- a/drivers/pci/pcie/ptm.c
> > +++ b/drivers/pci/pcie/ptm.c
> > @@ -44,6 +44,7 @@ void pci_disable_ptm(struct pci_dev *dev)
> >         pci_read_config_word(dev, ptm + PCI_PTM_CTRL, &ctrl);
> >         ctrl &= ~(PCI_PTM_CTRL_ENABLE | PCI_PTM_CTRL_ROOT);
> >         pci_write_config_word(dev, ptm + PCI_PTM_CTRL, ctrl);
> > +       dev->ptm_enabled = 0;
>
> -> I don't think that this is going to work without setting
> dev->ptm_enabled in pci_restore_ptm_state() if the restored state
> turns out to be "enabled".

And arguably, this function doesn't need to do anything if
dev->ptm_enabled is 0 already and this is the only check it needs to
do, because dev->ptm_enabled will only be set for PCIe devices that
have PTM.

> >  }
> >
> >  void pci_save_ptm_state(struct pci_dev *dev)
> > --