Re: [PATCH v1] PCI: Wait for device readiness after D3hot -> D0uninitialized transition

[Rafael J. Wysocki]

On Fri, May 15, 2026 at 1:41 PM Mika Westerberg
<mika.westerberg@xxxxxxxxxxxxxxx> wrote:
>
> On Thu, May 14, 2026 at 04:38:11PM -0500, Bjorn Helgaas wrote:
> > On Thu, May 14, 2026 at 08:06:25PM +0000, sashiko-bot@xxxxxxxxxx wrote:
> > > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> > > - [High] Ignored return value of `pci_dev_wait()` masks hardware readiness timeouts
> > > --
> > >
> > > commit 606c3a6294de4df52ee7dc27a7792cef6c8f72c4
> > > Author: Bjorn Helgaas <helgaas@xxxxxxxxxx>
> > >
> > > PCI: Wait for device readiness after D3hot -> D0uninitialized transition
> > >
> > > This commit adds a call to pci_dev_wait() after transitioning a device from
> > > D3hot to D0uninitialized. This ensures the device is ready to accept config
> > > accesses, especially for devices with No_Soft_Reset == 0.
> > >
> > > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > > > index 8f7cfcc000901..9d0fc9fbb76a0 100644
> > > > --- a/drivers/pci/pci.c
> > > > +++ b/drivers/pci/pci.c
> > > [ ... ]
> > > > @@ -1341,10 +1351,14 @@ int pci_power_up(struct pci_dev *dev)
> > > >   pci_write_config_word(dev, dev->pm_cap + PCI_PM_CTRL, 0);
> > > >
> > > >   /* Mandatory transition delays; see PCI PM 1.2. */
> > > > - if (state == PCI_D3hot)
> > > > + if (state == PCI_D3hot) {
> > > >           pci_dev_d3_sleep(dev);
> > > > - else if (state == PCI_D2)
> > > > +         if (!(pmcsr & PCI_PM_CTRL_NO_SOFT_RESET))
> > > > +                 pci_dev_wait(dev, "power up D3hot->D0uninitialized",
> > > > +                              PCIE_RESET_READY_POLL_MS);
> > >
> > > Is it safe to ignore the return value of pci_dev_wait() here?
> > >
> > > If the device times out or disconnects, pci_dev_wait() returns -ENOTTY. By
> > > ignoring this error, pci_power_up() continues, unconditionally sets
> > > dev->current_state = PCI_D0, and can return success (1 for need_restore).
> > >
> > > If pci_power_up() returns success, will callers like pci_back_from_sleep()
> > > execute pci_restore_state() against an unresponsive device, which could
> > > potentially trigger PCIe Master Aborts, AER events, or system crashes?
> > >
> > > Should pci_power_up() propagate the error from pci_dev_wait() to prevent
> > > this?
> >
> > Good point.  I think it should look like this instead:
> >
> >     if (state == PCI_D3hot) {
> >             pci_dev_d3_sleep(dev);
> >             if (!(pmcsr & PCI_PM_CTRL_NO_SOFT_RESET)) {
> >                     ret = pci_dev_wait(dev, "power up D3hot->D0uninitialized",
> >                                        PCIE_RESET_READY_POLL_MS);
> >                     if (ret) {
> >                             pci_err(dev, "Not ready after soft reset\n");
> >                             dev->current_state = PCI_D3cold;
>
> I wonder if PCI_POWER_ERROR makes sense here?

Not really, PCI_POWER_ERROR is mostly used by things like
"target_state" to indicate that nothing has been selected.

> >                             return -EIO;
> >                     }
> >             }
> >     } else if (state == PCI_D2) {
> >             udelay(PCI_PM_D2_DELAY);
> >     }
> >
> > > > + } else if (state == PCI_D2) {
> > > >           udelay(PCI_PM_D2_DELAY);
> > > > + }
> > > >
> > > >  end:
> > > >   dev->current_state = PCI_D0;
> > >
> > > --
> > > Sashiko AI review · https://sashiko.dev/#/patchset/20260514153124.404060-1-bhelgaas@xxxxxxxxxx?part=1