PCI: Add PCIE_LNKCAP2_SLS2SPEED() macro

Add PCIE_LNKCAP2_SLS2SPEED macro for transforming raw Link Capabilities 2
values to the pci_bus_speed. This is next to PCIE_SPEED2MBS_ENC() to make
it easier to update both places when adding support for new speeds.

Link: https://lore.kernel.org/r/1581937984-40353-10-git-send-email-yangyicong@hisilicon.com
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 421587b..e79cccb 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5784,19 +5784,10 @@
 	 * where only 2.5 GT/s and 5.0 GT/s speeds were defined.
 	 */
 	pcie_capability_read_dword(dev, PCI_EXP_LNKCAP2, &lnkcap2);
-	if (lnkcap2) { /* PCIe r3.0-compliant */
-		if (lnkcap2 & PCI_EXP_LNKCAP2_SLS_32_0GB)
-			return PCIE_SPEED_32_0GT;
-		else if (lnkcap2 & PCI_EXP_LNKCAP2_SLS_16_0GB)
-			return PCIE_SPEED_16_0GT;
-		else if (lnkcap2 & PCI_EXP_LNKCAP2_SLS_8_0GB)
-			return PCIE_SPEED_8_0GT;
-		else if (lnkcap2 & PCI_EXP_LNKCAP2_SLS_5_0GB)
-			return PCIE_SPEED_5_0GT;
-		else if (lnkcap2 & PCI_EXP_LNKCAP2_SLS_2_5GB)
-			return PCIE_SPEED_2_5GT;
-		return PCI_SPEED_UNKNOWN;
-	}
+
+	/* PCIe r3.0-compliant */
+	if (lnkcap2)
+		return PCIE_LNKCAP2_SLS2SPEED(lnkcap2);
 
 	pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnkcap);
 	if ((lnkcap & PCI_EXP_LNKCAP_SLS) == PCI_EXP_LNKCAP_SLS_5_0GB)
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 01f5d7f..75d027e 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -292,6 +292,15 @@
 struct pci_bus *pci_bus_get(struct pci_bus *bus);
 void pci_bus_put(struct pci_bus *bus);
 
+/* PCIe link information from Link Capabilities 2 */
+#define PCIE_LNKCAP2_SLS2SPEED(lnkcap2) \
+	((lnkcap2) & PCI_EXP_LNKCAP2_SLS_32_0GB ? PCIE_SPEED_32_0GT : \
+	 (lnkcap2) & PCI_EXP_LNKCAP2_SLS_16_0GB ? PCIE_SPEED_16_0GT : \
+	 (lnkcap2) & PCI_EXP_LNKCAP2_SLS_8_0GB ? PCIE_SPEED_8_0GT : \
+	 (lnkcap2) & PCI_EXP_LNKCAP2_SLS_5_0GB ? PCIE_SPEED_5_0GT : \
+	 (lnkcap2) & PCI_EXP_LNKCAP2_SLS_2_5GB ? PCIE_SPEED_2_5GT : \
+	 PCI_SPEED_UNKNOWN)
+
 /* PCIe speed to Mb/s reduced by encoding overhead */
 #define PCIE_SPEED2MBS_ENC(speed) \
 	((speed) == PCIE_SPEED_32_0GT ? 32000*128/130 : \