[PATCH] power: sequencing: pwrseq-pcie-m2: Support PCIe switch topologies

[Wei Deng <wei.deng@oss.qualcomm.com>]

The PCI parent OF node check in pwrseq_pcie_m2_notify() and
pwrseq_pcie_m2_create_serdev() only looks at the immediate parent of the
PCI endpoint device. This fails when a PCIe switch inserts one or more
intermediate bridges between the root port and the endpoint.

For example, on lemans-evk with IFP Mezzanine board, the Toshiba TC9562
PCIe switch creates two bridge devices (upstream and downstream ports)
without OF nodes, so the WCN6855 BT device appears at depth 3 and its
immediate parent has of_node=NULL.

Add a helper pwrseq_pcie_m2_pci_parent_matches() that walks the PCI
parent chain upward until it finds a device whose OF node matches the
expected connector port node, or reaches a non-PCI device. Replace both
single-level checks with this helper to handle arbitrary PCIe switch
depths.

Signed-off-by: Wei Deng <wei.deng@oss.qualcomm.com>
---
 drivers/power/sequencing/pwrseq-pcie-m2.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/power/sequencing/pwrseq-pcie-m2.c b/drivers/power/sequencing/pwrseq-pcie-m2.c
index de9848a9a9f1..82ba309ba5f3 100644
--- a/drivers/power/sequencing/pwrseq-pcie-m2.c
+++ b/drivers/power/sequencing/pwrseq-pcie-m2.c
@@ -376,6 +376,21 @@ static void pwrseq_pcie_m2_remove_serdev(struct pwrseq_pcie_m2_ctx *ctx,
 	mutex_unlock(&ctx->list_lock);
 }
 
+static bool pwrseq_pcie_m2_pci_parent_matches(struct pci_dev *pdev,
+					       struct device_node *pci_parent)
+{
+	struct device *dev = pdev->dev.parent;
+
+	while (dev) {
+		if (dev->of_node == pci_parent)
+			return true;
+		if (!dev_is_pci(dev))
+			break;
+		dev = dev->parent;
+	}
+	return false;
+}
+
 static int pwrseq_pcie_m2_notify(struct notifier_block *nb, unsigned long action,
 			      void *data)
 {
@@ -390,7 +405,7 @@ static int pwrseq_pcie_m2_notify(struct notifier_block *nb, unsigned long action
 	 */
 	struct device_node *pci_parent __free(device_node) =
 			of_graph_get_remote_node(dev_of_node(ctx->dev), 0, 0);
-	if (!pci_parent || (pci_parent != pdev->dev.parent->of_node))
+	if (!pci_parent || !pwrseq_pcie_m2_pci_parent_matches(pdev, pci_parent))
 		return NOTIFY_DONE;
 
 	switch (action) {
@@ -464,7 +479,7 @@ static int pwrseq_pcie_m2_create_serdev(struct pwrseq_pcie_m2_ctx *ctx)
 
 	/* Create serdev for existing PCI devices if required */
 	for_each_pci_dev(pdev) {
-		if (!pdev->dev.parent || pci_parent != pdev->dev.parent->of_node)
+		if (!pwrseq_pcie_m2_pci_parent_matches(pdev, pci_parent))
 			continue;
 
 		if (!pci_match_id(pwrseq_m2_pci_ids, pdev))
-- 
2.34.1