linux-kernel - [PATCH v3] PCI: loongson: skip scanning unavailable child device

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Date:   Fri,  4 Nov 2022 18:53:40 +0800
From:   Liu Peibao <liupeibao@...ngson.cn>
To:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>
Cc:     Huacai Chen <chenhuacai@...ngson.cn>,
        Jianmin Lv <lvjianmin@...ngson.cn>,
        Yinbo Zhu <zhuyinbo@...ngson.cn>,
        Liu Peibao <liupeibao@...ngson.cn>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3] PCI: loongson: skip scanning unavailable child device

The PCI Controller of 2k1000 could not mask devices by
setting vender id or device id in configuration space header
as invalid values. When there are pins shareble between
the platform device and PCI device, if the platform device
is preferred, we should not scan this PCI device. In the
above scene, add `status = "disabled"` property in DT node
of this PCI device.

Signed-off-by: Liu Peibao <liupeibao@...ngson.cn>
---
V2 -> V3: 1. use list_for_each_entry() for more clearly.
          2. fix wrong use of sizeof().
V1 -> V2: use existing property "status" instead of adding new property.


 drivers/pci/controller/pci-loongson.c | 55 +++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
index 05c50408f13b..c7dd88eac885 100644
--- a/drivers/pci/controller/pci-loongson.c
+++ b/drivers/pci/controller/pci-loongson.c
@@ -40,11 +40,21 @@ struct loongson_pci_data {
 	struct pci_ops *ops;
 };
 
+#ifdef CONFIG_OF
+struct mask_entry {
+	struct list_head entry;
+	unsigned int devfn;
+};
+#endif
+
 struct loongson_pci {
 	void __iomem *cfg0_base;
 	void __iomem *cfg1_base;
 	struct platform_device *pdev;
 	const struct loongson_pci_data *data;
+#ifdef CONFIG_OF
+	struct list_head masklist;
+#endif
 };
 
 /* Fixup wrong class code in PCIe bridges */
@@ -194,6 +204,18 @@ static void __iomem *pci_loongson_map_bus(struct pci_bus *bus,
 			return NULL;
 	}
 
+#ifdef CONFIG_OF
+	/* Don't access devices in masklist */
+	if (pci_is_root_bus(bus)) {
+		struct mask_entry *entry;
+
+		list_for_each_entry(entry, &priv->masklist, entry) {
+			if (devfn == entry->devfn)
+				return NULL;
+		}
+	}
+#endif
+
 	/* CFG0 can only access standard space */
 	if (where < PCI_CFG_SPACE_SIZE && priv->cfg0_base)
 		return cfg0_map(priv, bus, devfn, where);
@@ -206,6 +228,36 @@ static void __iomem *pci_loongson_map_bus(struct pci_bus *bus,
 }
 
 #ifdef CONFIG_OF
+static int setup_masklist(struct loongson_pci *priv)
+{
+	struct device *dev = &priv->pdev->dev;
+	struct device_node *dn, *parent = dev->of_node;
+	struct mask_entry *entry;
+	int devfn;
+
+	INIT_LIST_HEAD(&priv->masklist);
+
+	for_each_child_of_node(parent, dn) {
+		/*
+		 * if device is not available, add this to masklist
+		 * to avoid scanning it.
+		 */
+		if (!of_device_is_available(dn)) {
+			devfn = of_pci_get_devfn(dn);
+			if (devfn < 0)
+				continue;
+
+			entry = devm_kzalloc(dev, sizeof(*entry), GFP_KERNEL);
+			if (!entry)
+				return -ENOMEM;
+
+			entry->devfn = devfn;
+			list_add_tail(&entry->entry, &priv->masklist);
+		}
+	}
+
+	return 0;
+}
 
 static int loongson_map_irq(const struct pci_dev *dev, u8 slot, u8 pin)
 {
@@ -305,6 +357,9 @@ static int loongson_pci_probe(struct platform_device *pdev)
 		}
 	}
 
+	if (setup_masklist(priv))
+		return -ENOMEM;
+
 	bridge->sysdata = priv;
 	bridge->ops = priv->data->ops;
 	bridge->map_irq = loongson_map_irq;
-- 
2.20.1