Subject: [PATCH] PCI: Add link_disable in /sysfs for pcie device

Found PCIe cards from one vendor, will not respond to scan from bridge,
if we change bus number setting in bridge device.

Have to do link disable/enable on the pcie root port.

So try to expose link disable bit of pcie link control register. We can use
 echo 1 > /sys/..../link_disable
 echo 0 > /sys/..../link_disable
to bring the pcie device back to respond to scan.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 drivers/pci/pcie-sysfs.c |   33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

Index: linux-2.6/drivers/pci/pcie-sysfs.c
===================================================================
--- linux-2.6.orig/drivers/pci/pcie-sysfs.c
+++ linux-2.6/drivers/pci/pcie-sysfs.c
@@ -1,7 +1,35 @@
 #include <linux/kernel.h>
 #include <linux/pci.h>
 
+static ssize_t
+pcie_link_disable_show(struct device *dev, struct device_attribute *attr,
+			char *buf)
+{
+	struct pci_dev *pdev = to_pci_dev(dev);
+
+	return sprintf(buf, "%u\n", pcie_link_disable_get(pdev));
+}
+static ssize_t
+pcie_link_disable_store(struct device *dev, struct device_attribute *attr,
+			const char *buf, size_t count)
+{
+	struct pci_dev *pdev = to_pci_dev(dev);
+	unsigned long val;
+
+	if (kstrtoul(buf, 0, &val) < 0)
+		return -EINVAL;
+
+	pcie_link_disable_set(pdev, val);
+
+	return count;
+}
+
+static struct device_attribute pcie_link_disable_attr =
+		__ATTR(pcie_link_disable, 0644,
+		       pcie_link_disable_show, pcie_link_disable_store);
+
 static struct attribute *pci_dev_pcie_dev_attrs[] = {
+	&pcie_link_disable_attr.attr,
 	NULL,
 };
 
@@ -14,6 +42,11 @@ static umode_t pci_dev_pcie_attrs_are_vi
 	if (!pci_is_pcie(pdev))
 		return 0;
 
+	if (a == &pcie_link_disable_attr.attr)
+		if ((pci_pcie_type(pdev) != PCI_EXP_TYPE_ROOT_PORT) &&
+		    (pci_pcie_type(pdev) != PCI_EXP_TYPE_DOWNSTREAM))
+			return 0;
+
 	return a->mode;
 }