e1000e : Correct Rx Threshold granularity

In e1000e driver, Rx descriptor queue is used such that hardware can add only
one descriptor at a time. So the WTHRESH granularity in RXDCTL should be set
to single descriptor. This would ensure that every time controller fills a Rx
descriptor, it is flushed to host memory. Earlier this granularity was in
cache line units i.e 2 descriptors. This leads to controller always waiting
for 2 descriptors before flushing them out. But since not more than one Rx BD
is actually available , the accumulation condition never gets hit.

Signed-off-by: Ruchika Gupta <ruchika.gupta@freescale.com>
Signed-off-by: Vakul Garg <vakul@freescale.com>
Acked-by: Roy Zang <tie-fei.zang@freescale.com>

diff --git a/drivers/net/e1000.c b/drivers/net/e1000.c
index 2d4da4b386dd98caa822a3ecfa8417e396a0fc96..8ba98b27d52283be000f0896f838ca5e13eba591 100644 (file)
--- a/drivers/net/e1000.c
+++ b/drivers/net/e1000.c
@@ -1688,6 +1688,16 @@ e1000_init_hw(struct eth_device *nic)
                E1000_WRITE_REG(hw, TXDCTL, ctrl);
        }
 
+       /* Set the receive descriptor write back policy */
+
+       if (hw->mac_type >= e1000_82571) {
+               ctrl = E1000_READ_REG(hw, RXDCTL);
+               ctrl =
+                   (ctrl & ~E1000_RXDCTL_WTHRESH) |
+                   E1000_RXDCTL_FULL_RX_DESC_WB;
+               E1000_WRITE_REG(hw, RXDCTL, ctrl);
+       }
+
        switch (hw->mac_type) {
        default:
                break;

diff --git a/drivers/net/e1000.h b/drivers/net/e1000.h
index fd1d8f8717f2c90dc5b45cd869b52edfe6a224f9..1bbae5085ac9dac0fbf431c1c4bb8f231e50e9c1 100644 (file)
--- a/drivers/net/e1000.h
+++ b/drivers/net/e1000.h
@@ -1551,6 +1551,7 @@ struct e1000_hw {
 #define E1000_RXDCTL_HTHRESH 0x00003F00        /* RXDCTL Host Threshold */
 #define E1000_RXDCTL_WTHRESH 0x003F0000        /* RXDCTL Writeback Threshold */
 #define E1000_RXDCTL_GRAN    0x01000000        /* RXDCTL Granularity */
+#define E1000_RXDCTL_FULL_RX_DESC_WB 0x01010000        /* GRAN=1, WTHRESH=1 */
 
 /* Transmit Descriptor Control */
 #define E1000_TXDCTL_PTHRESH 0x0000003F        /* TXDCTL Prefetch Threshold */