[PATCH] sky2: receive queue watermark tweak

This patch makes the receive performance on some systems go from
714MB/s to 941MB/s. It adjusts the watermark of the receive queue
to be lower, thereby avoiding excess hardware flow control. This is
most important on the systems which have little/no additional buffering.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

2 files changed, 9 insertions, 3 deletions

diff --git a/drivers/net/sky2.c b/drivers/net/sky2.c
index b9f7eb5453f1..a8e096393a41 100644
--- a/drivers/net/sky2.c
+++ b/drivers/net/sky2.c
@@ -1062,11 +1062,16 @@ static int sky2_rx_start(struct sky2_port *sky2)
         sky2->rx_put = sky2->rx_next = 0;
         sky2_qset(hw, rxq);
 
+        /* On PCI express lowering the watermark gives better performance */
+        if (pci_find_capability(hw->pdev, PCI_CAP_ID_EXP))
+                sky2_write32(hw, Q_ADDR(rxq, Q_WM), BMU_WM_PEX);
+
+        /* These chips have no ram buffer?
+         * MAC Rx RAM Read is controlled by hardware */
         if (hw->chip_id == CHIP_ID_YUKON_EC_U &&
-            (hw->chip_rev == CHIP_REV_YU_EC_U_A1 || hw->chip_rev == CHIP_REV_YU_EC_U_B0)) {
-                /* MAC Rx RAM Read is controlled by hardware */
+            (hw->chip_rev == CHIP_REV_YU_EC_U_A1
+             || hw->chip_rev == CHIP_REV_YU_EC_U_B0))
                 sky2_write32(hw, Q_ADDR(rxq, Q_F), F_M_RX_RAM_DIS);
-        }
 
         sky2_prefetch_init(hw, rxq, sky2->rx_le_map, RX_LE_SIZE - 1);
 
diff --git a/drivers/net/sky2.h b/drivers/net/sky2.h
index 7760545edbf2..a63f6057b2ea 100644
--- a/drivers/net/sky2.h
+++ b/drivers/net/sky2.h
@@ -680,6 +680,7 @@ enum {
                           BMU_FIFO_ENA | BMU_OP_ON,
 
         BMU_WM_DEFAULT = 0x600,
+        BMU_WM_PEX     = 0x80,
 };
 
 /* Tx BMU Control / Status Registers (Yukon-2) */