[Intel-xe] [PATCH] drm/xe/pm: WARN_ON() on unbounded pcie parent bridge device

[Gupta, Anshuman]

> -----Original Message-----
> From: Vivi, Rodrigo <rodrigo.vivi at intel.com>
> Sent: Monday, May 8, 2023 10:45 PM
> To: Gupta, Anshuman <anshuman.gupta at intel.com>
> Cc: intel-xe at lists.freedesktop.org
> Subject: Re: [Intel-xe] [PATCH] drm/xe/pm: WARN_ON() on unbounded pcie
> parent bridge device
> 
> On Mon, May 08, 2023 at 02:47:34PM +0530, Anshuman Gupta wrote:
> > Intel Discrete GFX cards gfx may have multiple PCIe endpoints, they
> > connects to root port via pcie upstream switch port(USP) and virtual
> > pcie switch port(VSP), sometimes VSP pcie devices doesn't bind to
> > pcieport driver. Without pcieport driver pcie PM comes without any
> > warranty and with unbounded VSP gfx card won't transition to low power
> > pcie device and link state therefore assert drm_WARN_ON() on
> unbounded
> > VSP.
> >
> > Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > Signed-off-by: Anshuman Gupta <anshuman.gupta at intel.com>
> > ---
> >  drivers/gpu/drm/xe/xe_pci.c | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/xe/xe_pci.c b/drivers/gpu/drm/xe/xe_pci.c
> > index 19ead642442e..dc0d5cb4950b 100644
> > --- a/drivers/gpu/drm/xe/xe_pci.c
> > +++ b/drivers/gpu/drm/xe/xe_pci.c
> > @@ -667,12 +667,24 @@ static void xe_pci_shutdown(struct pci_dev
> *pdev)
> >  	xe_device_shutdown(pdev_to_xe_device(pdev));
> >  }
> >
> > +static void xe_assert_on_unbounded_bridge(struct pci_dev *pdev) {
> > +	struct pci_dev *bridge = pci_upstream_bridge(pdev);
> > +	struct xe_device *xe = pdev_to_xe_device(pdev);
> > +
> > +	if (!bridge)
> > +		return;
> > +
> > +	drm_WARN_ON(&xe->drm, !bridge->driver); }
> > +
> >  #ifdef CONFIG_PM_SLEEP
> >  static int xe_pci_suspend(struct device *dev)  {
> >  	struct pci_dev *pdev = to_pci_dev(dev);
> >  	int err;
> >
> > +	xe_assert_on_unbounded_bridge(pdev);
> 
> besides warning, shouldn't we block the suspend at all?
> returning from this point...
If that is desired then, we shall check this in xe probe and initializes the PM OPS with NULL rather then failing suspend ?
Br,
Anshuman Gupta. 
> 
> >  	err = xe_pm_suspend(pdev_to_xe_device(pdev));
> >  	if (err)
> >  		return err;
> > @@ -718,6 +730,7 @@ static int xe_pci_runtime_suspend(struct device
> *dev)
> >  	struct xe_device *xe = pdev_to_xe_device(pdev);
> >  	int err;
> >
> > +	xe_assert_on_unbounded_bridge(pdev);
> >  	err = xe_pm_runtime_suspend(xe);
> >  	if (err)
> >  		return err;
> > --
> > 2.38.0
> >