linux-kernel - [PATCH 2/3] PCI: apple: Probe all GPIOs for availability first

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Message-Id: <20220502093832.32778-3-marcan@marcan.st>
Date:   Mon,  2 May 2022 18:38:31 +0900
From:   Hector Martin <marcan@...can.st>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Hector Martin <marcan@...can.st>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Sven Peter <sven@...npeter.dev>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: [PATCH 2/3] PCI: apple: Probe all GPIOs for availability first

If we're probing the PCI controller and some GPIOs are not available and
cause a probe defer, we can end up leaving some ports initialized and
not others and making a mess.

Check for PERST# GPIOs for all ports first, and just return
-EPROBE_DEFER if any are not ready yet, without bringing anything up.

Fixes: 1e33888fbe44 ("PCI: apple: Add initial hardware bring-up")
Cc: stable@...r.kernel.org
Signed-off-by: Hector Martin <marcan@...can.st>
---
 drivers/pci/controller/pcie-apple.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/pci/controller/pcie-apple.c b/drivers/pci/controller/pcie-apple.c
index e0c06c0ee731..e3aa2d461739 100644
--- a/drivers/pci/controller/pcie-apple.c
+++ b/drivers/pci/controller/pcie-apple.c
@@ -507,6 +507,20 @@ static u32 apple_pcie_rid2sid_write(struct apple_pcie_port *port,
 	return readl_relaxed(port->base + PORT_RID2SID(idx));
 }
 
+static int apple_pcie_probe_port(struct device_node *np)
+{
+	struct gpio_desc *gd;
+
+	gd = gpiod_get_from_of_node(np, "reset-gpios", 0,
+				    GPIOD_OUT_LOW, "PERST#");
+	if (IS_ERR(gd)) {
+		return PTR_ERR(gd);
+	}
+
+	gpiod_put(gd);
+	return 0;
+}
+
 static int apple_pcie_setup_port(struct apple_pcie *pcie,
 				 struct device_node *np)
 {
@@ -797,8 +811,18 @@ static int apple_pcie_init(struct pci_config_window *cfg)
 
 static int apple_pcie_probe(struct platform_device *pdev)
 {
+	struct device *dev = &pdev->dev;
+	struct device_node *of_port;
 	int ret;
 
+	/* Check for probe dependencies for all ports first */
+	for_each_child_of_node(dev->of_node, of_port) {
+		ret = apple_pcie_probe_port(of_port);
+		of_node_put(of_port);
+		if (ret)
+			return dev_err_probe(dev, ret, "Port %pOF probe fail\n", of_port);
+	}
+
 	ret = bus_register_notifier(&pci_bus_type, &apple_pcie_nb);
 	if (ret)
 		return ret;
-- 
2.35.1