[net-next 02/12] e1000e: slow performance between two 82579 connected via 10Mbit hub
From: Jeff Kirsher <hidden>
Date: 2013-03-28 09:00:21
Subsystem:
intel ethernet drivers, networking drivers, the rest · Maintainers:
Tony Nguyen, Przemek Kitszel, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Bruce Allan <redacted> 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 <redacted> Tested-by: Jeff Pieper <redacted> Signed-off-by: Jeff Kirsher <redacted> --- drivers/net/ethernet/intel/e1000e/defines.h | 1 + drivers/net/ethernet/intel/e1000e/ich8lan.c | 28 ++++++++++++++++++++++++++++ drivers/net/ethernet/intel/e1000e/ich8lan.h | 1 + 3 files changed, 30 insertions(+)
diff --git a/drivers/net/ethernet/intel/e1000e/defines.h b/drivers/net/ethernet/intel/e1000e/defines.h
index a6aeb19..351c94a 100644
--- a/drivers/net/ethernet/intel/e1000e/defines.h
+++ b/drivers/net/ethernet/intel/e1000e/defines.h@@ -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 */
diff --git a/drivers/net/ethernet/intel/e1000e/ich8lan.c b/drivers/net/ethernet/intel/e1000e/ich8lan.c
index 1cdec5f..4f2f0f6 100644
--- a/drivers/net/ethernet/intel/e1000e/ich8lan.c
+++ b/drivers/net/ethernet/intel/e1000e/ich8lan.c@@ -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)) {
diff --git a/drivers/net/ethernet/intel/e1000e/ich8lan.h b/drivers/net/ethernet/intel/e1000e/ich8lan.h
index 8bf4655..00ba6c9 100644
--- a/drivers/net/ethernet/intel/e1000e/ich8lan.h
+++ b/drivers/net/ethernet/intel/e1000e/ich8lan.h@@ -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 */
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1.7.11.7