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

[Bjorn Helgaas]

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;
                            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