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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
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@@ -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 */