[PATCH] PCI: qcom: Handle mixed PERST#/PHY DT configuration

[Qiang Yu]

The driver currently supports two PERST# and PHY DT configuration. In one
case, PHY, PERST#, are described in the RC node. In the other case, they
are described in the RP node.

A mixed setup is not supported. One common example is PHY on the RP node
while PERST# remains on the RC node. In that case the driver goes through
the RP parse path, does not find PERST# on RP, and does not report an
error because PERST# is optional. Probe can then succeed silently while
PERST# is left uncontrolled, and PCIe endpoints fails to work later. This
silent probe success makes debugging difficult.

Handle this mixed case in the RP parse path by checking whether PERST# is
present on RC and, if so, using the RC PERST# GPIO for RP ports while
keeping RP parsing for PHY. Emit a warning to indicate mixed DT content so
it can be fixed.

This keeps mixed systems functional and makes the configuration issue
visible instead of failing later at endpoint bring-up.

Suggested-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxxxxxxxx>
Signed-off-by: Qiang Yu <qiang.yu@xxxxxxxxxxxxxxxx>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index 9fdfc88ac151..8235961d692f 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -282,6 +282,7 @@ struct qcom_pcie {
 	const struct qcom_pcie_cfg *cfg;
 	struct dentry *debugfs;
 	struct list_head ports;
+	struct gpio_desc *reset;
 	bool suspended;
 	bool use_pm_opp;
 };
@@ -1703,6 +1704,11 @@ static int qcom_pcie_parse_perst(struct qcom_pcie *pcie,
 	struct gpio_desc *reset;
 	int ret;
 
+	if (pcie->reset) {
+		reset = pcie->reset;
+		goto skip_perst_parsing;
+	}
+
 	if (!of_find_property(np, "reset-gpios", NULL))
 		goto parse_child_node;
 
@@ -1721,6 +1727,7 @@ static int qcom_pcie_parse_perst(struct qcom_pcie *pcie,
 		return PTR_ERR(reset);
 	}
 
+skip_perst_parsing:
 	perst = devm_kzalloc(dev, sizeof(*perst), GFP_KERNEL);
 	if (!perst)
 		return -ENOMEM;
@@ -1778,6 +1785,14 @@ static int qcom_pcie_parse_ports(struct qcom_pcie *pcie)
 	struct device *dev = pcie->pci->dev;
 	int ret = -ENODEV;
 
+	if (of_find_property(dev->of_node, "perst-gpios", NULL)) {
+		pcie->reset = devm_gpiod_get_optional(dev, "perst", GPIOD_OUT_HIGH);
+		if (IS_ERR(pcie->reset))
+			return PTR_ERR(pcie->reset);
+
+		dev_warn(dev, "Reusing PERST# from Root Complex node. DT needs to be fixed!\n");
+	}
+
 	for_each_available_child_of_node_scoped(dev->of_node, of_port) {
 		if (!of_node_is_type(of_port, "pci"))
 			continue;

---
base-commit: 33a76fc3c3e61386524479b99f35423bd3d9a895
change-id: 20260508-mix_perst_phy_dts-b741b840833b

Best regards,
--  
Qiang Yu <qiang.yu@xxxxxxxxxxxxxxxx>