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

[Mika Westerberg <mika.westerberg@linux.intel.com>]

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@kernel.org 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@kernel.org>
> > 
> > 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?

>                             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@google.com?part=1