e1000: add PCI-E capability detection code

Add code to display the detected PCI-E bus width.
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>

drivers/net/e1000/e1000_hw.c

@@ -6556,6 +6556,8 @@ e1000_tbi_adjust_stats(struct e1000_hw *hw,
 void
 e1000_get_bus_info(struct e1000_hw *hw)
 {
+    int32_t ret_val;
+    uint16_t pci_ex_link_status;
     uint32_t status;
 
     switch (hw->mac_type) {
@@ -6565,18 +6567,25 @@ e1000_get_bus_info(struct e1000_hw *hw)
         hw->bus_speed = e1000_bus_speed_unknown;
         hw->bus_width = e1000_bus_width_unknown;
         break;
+    case e1000_82571:
     case e1000_82572:
     case e1000_82573:
+    case e1000_80003es2lan:
         hw->bus_type = e1000_bus_type_pci_express;
         hw->bus_speed = e1000_bus_speed_2500;
-        hw->bus_width = e1000_bus_width_pciex_1;
+        ret_val = e1000_read_pcie_cap_reg(hw,
+                                      PCI_EX_LINK_STATUS,
+                                      &pci_ex_link_status);
+        if (ret_val)
+            hw->bus_width = e1000_bus_width_unknown;
+        else
+            hw->bus_width = (pci_ex_link_status & PCI_EX_LINK_WIDTH_MASK) >>
+                          PCI_EX_LINK_WIDTH_SHIFT;
         break;
-    case e1000_82571:
     case e1000_ich8lan:
-    case e1000_80003es2lan:
         hw->bus_type = e1000_bus_type_pci_express;
         hw->bus_speed = e1000_bus_speed_2500;
-        hw->bus_width = e1000_bus_width_pciex_4;
+        hw->bus_width = e1000_bus_width_pciex_1;
         break;
     default:
         status = E1000_READ_REG(hw, STATUS);

drivers/net/e1000/e1000_hw.h

@@ -418,6 +418,7 @@ void e1000_pci_set_mwi(struct e1000_hw *hw);
 void e1000_pci_clear_mwi(struct e1000_hw *hw);
 void e1000_read_pci_cfg(struct e1000_hw *hw, uint32_t reg, uint16_t * value);
 void e1000_write_pci_cfg(struct e1000_hw *hw, uint32_t reg, uint16_t * value);
+int32_t e1000_read_pcie_cap_reg(struct e1000_hw *hw, uint32_t reg, uint16_t *value);
 /* Port I/O is only supported on 82544 and newer */
 void e1000_io_write(struct e1000_hw *hw, unsigned long port, uint32_t value);
 int32_t e1000_disable_pciex_master(struct e1000_hw *hw);
@@ -2220,6 +2221,11 @@ struct e1000_host_command_info {
 #define E1000_FACTPS_LAN_FUNC_SEL                   0x40000000
 #define E1000_FACTPS_PM_STATE_CHANGED               0x80000000
 
+/* PCI-Ex Config Space */
+#define PCI_EX_LINK_STATUS           0x12
+#define PCI_EX_LINK_WIDTH_MASK       0x3F0
+#define PCI_EX_LINK_WIDTH_SHIFT      4
+
 /* EEPROM Commands - Microwire */
 #define EEPROM_READ_OPCODE_MICROWIRE  0x6  /* EEPROM read opcode */
 #define EEPROM_WRITE_OPCODE_MICROWIRE 0x5  /* EEPROM write opcode */

drivers/net/e1000/e1000_main.c

@@ -4473,6 +4473,22 @@ e1000_write_pci_cfg(struct e1000_hw *hw, uint32_t reg, uint16_t *value)
 	pci_write_config_word(adapter->pdev, reg, *value);
 }
 
+int32_t
+e1000_read_pcie_cap_reg(struct e1000_hw *hw, uint32_t reg, uint16_t *value)
+{
+    struct e1000_adapter *adapter = hw->back;
+    uint16_t cap_offset;
+
+    cap_offset = pci_find_capability(adapter->pdev, PCI_CAP_ID_EXP);
+    if (!cap_offset)
+        return -E1000_ERR_CONFIG;
+
+    pci_read_config_word(adapter->pdev, cap_offset + reg, value);
+
+    return E1000_SUCCESS;
+}
+
+
 void
 e1000_io_write(struct e1000_hw *hw, unsigned long port, uint32_t value)
 {