[PATCH 4/4] PCI: Add link_disable in /sysfs for pcie device

[Dirk Gouders]

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

diff --git a/drivers/pci/pcie-sysfs.c b/drivers/pci/pcie-sysfs.c
index b65e065..d4f6d4f 100644
--- a/drivers/pci/pcie-sysfs.c
+++ b/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_visible(struct kobject *kobj,
        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;
 }
 
-- 
2.1.0


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