tg3: Fix read DMA FIFO overruns on recent devices

Earlier versions of tg3 devices had a problem where the read DMA FIFO
could be overrun in certain edge conditions.  The fix was to limit the
number of rx BDs the hardware would fetch at a time.  For later devices
(5761, 5784 and later ASIC revs), there is a hardware fix that must be
enabled to fix the same problem.  This patch adds that hardware fix.

There is a gap in the ASIC revision lineage where neither fix is
applied.  This is intentional as these ASIC revisions are not afflicted
by the bug.

Reviewed-by: Benjamin Li <benli@broadcom.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/tg3.c

@@ -8015,6 +8015,16 @@ static int tg3_reset_hw(struct tg3 *tp, int reset_phy)
 	    GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_57780)
 		rdmac_mode |= RDMAC_MODE_IPV6_LSO_EN;
 
+	if (GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5761 ||
+	    GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5784 ||
+	    GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5785 ||
+	    GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_57780 ||
+	    (tp->tg3_flags3 & TG3_FLG3_5717_PLUS)) {
+		val = tr32(TG3_RDMA_RSRVCTRL_REG);
+		tw32(TG3_RDMA_RSRVCTRL_REG,
+		     val | TG3_RDMA_RSRVCTRL_FIFO_OFLW_FIX);
+	}
+
 	/* Receive/send statistics. */
 	if (tp->tg3_flags2 & TG3_FLG2_5750_PLUS) {
 		val = tr32(RCVLPC_STATS_ENABLE);

drivers/net/tg3.h

@@ -1302,7 +1302,11 @@
 #define  RDMAC_STATUS_FIFOURUN		 0x00000080
 #define  RDMAC_STATUS_FIFOOREAD		 0x00000100
 #define  RDMAC_STATUS_LNGREAD		 0x00000200
-/* 0x4808 --> 0x4c00 unused */
+/* 0x4808 --> 0x4900 unused */
+
+#define TG3_RDMA_RSRVCTRL_REG		0x00004900
+#define TG3_RDMA_RSRVCTRL_FIFO_OFLW_FIX	 0x00000004
+/* 0x4904 --> 0x4c00 unused */
 
 /* Write DMA control registers */
 #define WDMAC_MODE			0x00004c00