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

[Anshuman Gupta]

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);
 	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