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e1000e: slow performance between two 82579 connected via 10Mbit hub

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Two 82579 LOMs connected via a 10Mb hub experience extraordinarily low
performance.  This is because 82579 is excessively aggressive on transmit
at 10Mb half-duplex and will not provide sufficient time for the link
partner to transmit.  When the link partner is also 82579, the result is a
lot of collisions (and corresponding re-transmits) that cause the poor
performance. To work-around this issue, significantly increase the IPG in
the MAC to allow enough gap for the link partner to transmit and reduce the
Rx latency in the analog PHY to 0 to reduce the number of collisions.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
This commit is contained in:
Bruce Allan 2013-03-06 09:02:36 +00:00 committed by Jeff Kirsher
parent bb034512da
commit 772d05c51c
3 changed files with 30 additions and 0 deletions
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1
drivers/net/ethernet/intel/e1000e/defines.h
View File

@ -236,6 +236,7 @@
#define E1000_STATUS_FUNC_SHIFT 2
#define E1000_STATUS_FUNC_1 0x00000004 /* Function 1 */
#define E1000_STATUS_TXOFF 0x00000010 /* transmission paused */
#define E1000_STATUS_SPEED_MASK 0x000000C0
#define E1000_STATUS_SPEED_10 0x00000000 /* Speed 10Mb/s */
#define E1000_STATUS_SPEED_100 0x00000040 /* Speed 100Mb/s */
#define E1000_STATUS_SPEED_1000 0x00000080 /* Speed 1000Mb/s */

28
drivers/net/ethernet/intel/e1000e/ich8lan.c
View File

@ -871,6 +871,34 @@ static s32 e1000_check_for_copper_link_ich8lan(struct e1000_hw *hw)
return ret_val;
}
/* When connected at 10Mbps half-duplex, 82579 parts are excessively
* aggressive resulting in many collisions. To avoid this, increase
* the IPG and reduce Rx latency in the PHY.
*/
if ((hw->mac.type == e1000_pch2lan) && link) {
u32 reg;
reg = er32(STATUS);
if (!(reg & (E1000_STATUS_FD | E1000_STATUS_SPEED_MASK))) {
reg = er32(TIPG);
reg &= ~E1000_TIPG_IPGT_MASK;
reg |= 0xFF;
ew32(TIPG, reg);
/* Reduce Rx latency in analog PHY */
ret_val = hw->phy.ops.acquire(hw);
if (ret_val)
return ret_val;
ret_val =
e1000_write_emi_reg_locked(hw, I82579_RX_CONFIG, 0);
hw->phy.ops.release(hw);
if (ret_val)
return ret_val;
}
}
/* Work-around I218 hang issue */
if ((hw->adapter->pdev->device == E1000_DEV_ID_PCH_LPTLP_I218_LM) ||
(hw->adapter->pdev->device == E1000_DEV_ID_PCH_LPTLP_I218_V)) {

1
drivers/net/ethernet/intel/e1000e/ich8lan.h
View File

@ -211,6 +211,7 @@
#define I82579_MSE_THRESHOLD 0x084F /* 82579 Mean Square Error Threshold */
#define I82577_MSE_THRESHOLD 0x0887 /* 82577 Mean Square Error Threshold */
#define I82579_MSE_LINK_DOWN 0x2411 /* MSE count before dropping link */
#define I82579_RX_CONFIG 0x3412 /* Receive configuration */
#define I82579_EEE_PCS_STATUS 0x182D /* IEEE MMD Register 3.1 >> 8 */
#define I82579_EEE_CAPABILITY 0x0410 /* IEEE MMD Register 3.20 */
#define I82579_EEE_ADVERTISEMENT 0x040E /* IEEE MMD Register 7.60 */