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 --- Tested on P1010 and P4080 with 82572 and 82574 cards.

Changes in v2 - Fixed subject line and commit message

drivers/net/e1000.c | 10 ++++++++++ drivers/net/e1000.h | 1 + 2 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/drivers/net/e1000.c b/drivers/net/e1000.c index 98145bc..1f3c2b0 100644 --- a/drivers/net/e1000.c +++ b/drivers/net/e1000.c @@ -1703,6 +1703,16 @@ 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 720d8c6..cdb0e36 100644 --- a/drivers/net/e1000.h +++ b/drivers/net/e1000.h @@ -1518,6 +1518,7 @@ 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 */