e1000e: workaround hw errata

There is a hardware errata in some revisions of the 82574 that needs
to be worked around in the driver by setting a register bit at init.

If this bit is not set A0 versions of the 82574 can generate
tx hangs.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 6 insertions, 1 deletions

diff --git a/drivers/net/e1000e/82571.c b/drivers/net/e1000e/82571.c
index cf43ee743b3c..0890162953e9 100644
--- a/drivers/net/e1000e/82571.c
+++ b/drivers/net/e1000e/82571.c
@@ -981,11 +981,15 @@ static void e1000_initialize_hw_bits_82571(struct e1000_hw *hw)
                 ew32(PBA_ECC, reg);
         }
 
-        /* PCI-Ex Control Register */
+        /* PCI-Ex Control Registers */
         if (hw->mac.type == e1000_82574) {
                 reg = er32(GCR);
                 reg |= (1 << 22);
                 ew32(GCR, reg);
+
+                reg = er32(GCR2);
+                reg |= 1;
+                ew32(GCR2, reg);
         }
 
         return;
diff --git a/drivers/net/e1000e/hw.h b/drivers/net/e1000e/hw.h
index f25e961c6b3b..2d4ce0492df0 100644
--- a/drivers/net/e1000e/hw.h
+++ b/drivers/net/e1000e/hw.h
@@ -206,6 +206,7 @@ enum e1e_registers {
         E1000_MANC2H    = 0x05860, /* Management Control To Host - RW */
         E1000_SW_FW_SYNC = 0x05B5C, /* Software-Firmware Synchronization - RW */
         E1000_GCR       = 0x05B00, /* PCI-Ex Control */
+        E1000_GCR2      = 0x05B64, /* PCI-Ex Control #2 */
         E1000_FACTPS    = 0x05B30, /* Function Active and Power State to MNG */
         E1000_SWSM      = 0x05B50, /* SW Semaphore */
         E1000_FWSM      = 0x05B54, /* FW Semaphore */