[PATCH v5 1/3] PCI: host-common: Fix early bus-walk exit in d3cold_possible()

[Krishna Chaitanya Chundru]

__pci_host_common_d3cold_possible() returns -EOPNOTSUPP for the first
downstream device it finds outside PCI_D3hot, and pci_walk_bus() aborts
the walk as soon as its callback returns nonzero. Any device enumerated
after the disqualifying one -- including a wakeup-enabled, PME-from-D3cold
capable endpoint -- is then never visited, so pme_capable can come back
false even though such a device exists on the bus.

Since pci_host_common_d3cold_possible() already returns false whenever
any device disqualifies D3cold, aborting the walk buys nothing for the
plain suspend path: the overall bool result is unaffected. But it
silently drops pme_capable detection for any device ordered after the
disqualifying one.

This matters for the upcoming shutdown path in particular: unlike plain
suspend, shutdown forces the link into L2/D3cold regardless of whether
pci_host_common_d3cold_possible() itself allows it (see the following
"force_d3cold" changes), so at shutdown time it's common for an
endpoint to still be in D0 and disqualify D3cold while a later,
PME-capable device is never visited. dw_pcie_suspend_noirq() still
uses "pme_capable" to set pci->pp.skip_pwrctrl_off, so an inaccurate
result here can cause Vaux/wakeup support to be dropped for a device
that actually supports PME from D3cold.

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@xxxxxxxxxxxxxxxx>
---
 drivers/pci/controller/pci-host-common.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/pci/controller/pci-host-common.c b/drivers/pci/controller/pci-host-common.c
index a23907a875e5..78bc4c8c9656 100644
--- a/drivers/pci/controller/pci-host-common.c
+++ b/drivers/pci/controller/pci-host-common.c
@@ -274,22 +274,19 @@ static int __pci_host_common_d3cold_possible(struct pci_dev *pdev,
 	if (!pdev->dev.driver && !pci_is_enabled(pdev))
 		return 0;
 
-	if (pdev->current_state != PCI_D3hot)
-		goto exit;
+	if (pdev->current_state != PCI_D3hot) {
+		*flags &= ~PCI_HOST_D3COLD_ALLOWED;
+		return 0;
+	}
 
 	if (device_may_wakeup(&pdev->dev)) {
-		if (!pci_pme_capable(pdev, PCI_D3cold))
-			goto exit;
-		else
+		if (pci_pme_capable(pdev, PCI_D3cold))
 			*flags |= PCI_HOST_PME_D3COLD_CAPABLE;
+		else
+			*flags &= ~PCI_HOST_D3COLD_ALLOWED;
 	}
 
 	return 0;
-
-exit:
-	*flags &= ~PCI_HOST_D3COLD_ALLOWED;
-
-	return -EOPNOTSUPP;
 }
 
 /**

-- 
2.34.1