tg3: Fix 5719 internal FIFO overflow problem

Under load, there an internal FIFO can overflow on the 5719.  The fix is
to scale back the PCIe maximum read request size based on the current
link speed and width.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
index 2624d71..226e60d 100644
--- a/drivers/net/tg3.c
+++ b/drivers/net/tg3.c
@@ -6985,7 +6985,7 @@
 
 	if (GET_ASIC_REV(tp->pci_chip_rev_id) != ASIC_REV_5785) {
 		if (tp->tg3_flags2 & TG3_FLG2_PCI_EXPRESS)
-			pcie_set_readrq(tp->pdev, 4096);
+			pcie_set_readrq(tp->pdev, tp->pcie_readrq);
 		else {
 			pci_write_config_byte(tp->pdev, PCI_CACHE_LINE_SIZE,
 					      tp->pci_cacheline_sz);
@@ -7179,7 +7179,7 @@
 				      tp->pcie_cap + PCI_EXP_DEVCTL,
 				      val16);
 
-		pcie_set_readrq(tp->pdev, 4096);
+		pcie_set_readrq(tp->pdev, tp->pcie_readrq);
 
 		/* Clear error status */
 		pci_write_config_word(tp->pdev,
@@ -13366,7 +13366,45 @@
 
 		tp->tg3_flags2 |= TG3_FLG2_PCI_EXPRESS;
 
-		pcie_set_readrq(tp->pdev, 4096);
+		tp->pcie_readrq = 4096;
+		if (GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5719) {
+			u16 word;
+
+			pci_read_config_word(tp->pdev,
+					     tp->pcie_cap + PCI_EXP_LNKSTA,
+					     &word);
+			switch (word & PCI_EXP_LNKSTA_CLS) {
+			case PCI_EXP_LNKSTA_CLS_2_5GB:
+				word &= PCI_EXP_LNKSTA_NLW;
+				word >>= PCI_EXP_LNKSTA_NLW_SHIFT;
+				switch (word) {
+				case 2:
+					tp->pcie_readrq = 2048;
+					break;
+				case 4:
+					tp->pcie_readrq = 1024;
+					break;
+				}
+				break;
+
+			case PCI_EXP_LNKSTA_CLS_5_0GB:
+				word &= PCI_EXP_LNKSTA_NLW;
+				word >>= PCI_EXP_LNKSTA_NLW_SHIFT;
+				switch (word) {
+				case 1:
+					tp->pcie_readrq = 2048;
+					break;
+				case 2:
+					tp->pcie_readrq = 1024;
+					break;
+				case 4:
+					tp->pcie_readrq = 512;
+					break;
+				}
+			}
+		}
+
+		pcie_set_readrq(tp->pdev, tp->pcie_readrq);
 
 		pci_read_config_word(tp->pdev,
 				     tp->pcie_cap + PCI_EXP_LNKCTL,