[PATCH 10/18] PCI: Export pcie_get_speed() using the code from sysfs PCI link speed show function

[Dave Jiang <dave.jiang@xxxxxxxxx>]

Move the logic in current_link_speed_show() to a common function and export
that functiuon as pcie_get_speed() to allow other drivers to to retrieve
the current negotiated link speed.

Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>
---
 drivers/pci/pci-sysfs.c |   12 ++----------
 drivers/pci/pci.c       |   20 ++++++++++++++++++++
 include/linux/pci.h     |    1 +
 3 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index dd0d9d9bc509..0217bb5ca8fa 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -205,17 +205,9 @@ static ssize_t current_link_speed_show(struct device *dev,
 				       struct device_attribute *attr, char *buf)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);
-	u16 linkstat;
-	int err;
-	enum pci_bus_speed speed;
-
-	err = pcie_capability_read_word(pci_dev, PCI_EXP_LNKSTA, &linkstat);
-	if (err)
-		return -EINVAL;
 
-	speed = pcie_link_speed[linkstat & PCI_EXP_LNKSTA_CLS];
-
-	return sysfs_emit(buf, "%s\n", pci_speed_string(speed));
+	return sysfs_emit(buf, "%s\n",
+			  pci_speed_string(pcie_get_speed(pci_dev)));
 }
 static DEVICE_ATTR_RO(current_link_speed);
 
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index fba95486caaf..d0131b5623b1 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6215,6 +6215,26 @@ enum pcie_link_width pcie_get_width_cap(struct pci_dev *dev)
 }
 EXPORT_SYMBOL(pcie_get_width_cap);
 
+/**
+ * pcie_get_speed - query for the PCI device's current link speed
+ * @dev: PCI device to query
+ *
+ * Query the PCI device current link speed.
+ */
+enum pci_bus_speed pcie_get_speed(struct pci_dev *dev)
+{
+	u16 linkstat, cls;
+	int err;
+
+	err = pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &linkstat);
+	if (err)
+		return PCI_SPEED_UNKNOWN;
+
+	cls = FIELD_GET(PCI_EXP_LNKSTA_CLS, linkstat);
+	return pcie_link_speed[cls];
+}
+EXPORT_SYMBOL(pcie_get_speed);
+
 /**
  * pcie_bandwidth_capable - calculate a PCI device's link bandwidth capability
  * @dev: PCI device
diff --git a/include/linux/pci.h b/include/linux/pci.h
index adffd65e84b4..6a065986ff8f 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -303,6 +303,7 @@ enum pci_bus_speed {
 	PCI_SPEED_UNKNOWN		= 0xff,
 };
 
+enum pci_bus_speed pcie_get_speed(struct pci_dev *dev);
 enum pci_bus_speed pcie_get_speed_cap(struct pci_dev *dev);
 enum pcie_link_width pcie_get_width_cap(struct pci_dev *dev);