igb: use packet buffer sizes from RXPBS register

This patch changes the configuration for 82576 so that it uses the actual
value of the 82576 rx packet buffer size instead of just assuming the
value.
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/igb/e1000_82575.h

@@ -228,6 +228,8 @@ struct e1000_adv_tx_context_desc {
 
 #define ALL_QUEUES   0xFFFF
 
+/* RX packet buffer size defines */
+#define E1000_RXPBS_SIZE_MASK_82576  0x0000007F
 void igb_vmdq_set_loopback_pf(struct e1000_hw *, bool);
 void igb_vmdq_set_replication_pf(struct e1000_hw *, bool);
 

drivers/net/igb/e1000_regs.h

@@ -102,7 +102,9 @@
 #define E1000_ETQF(_n)  (0x05CB0 + (4 * (_n))) /* EType Queue Fltr */
 
 #define E1000_RQDPC(_n) (0x0C030 + ((_n) * 0x40))
+
 /* Split and Replication RX Control - RW */
+#define E1000_RXPBS    0x02404  /* Rx Packet Buffer Size - RW */
 /*
  * Convenience macros
  *

drivers/net/igb/igb_main.c

@@ -1215,7 +1215,8 @@ void igb_reset(struct igb_adapter *adapter)
 	 */
 	switch (mac->type) {
 	case e1000_82576:
-		pba = E1000_PBA_64K;
+		pba = rd32(E1000_RXPBS);
+		pba &= E1000_RXPBS_SIZE_MASK_82576;
 		break;
 	case e1000_82575:
 	default: