dm648 about SGMII to SGMII mode

I  use a customer board in my project.I use dm648 DSP.we do not use PHY instead  we use Broadcom switch chip 53115. The DSP is  used in SGMII to SGMII mode.But I found the rate of  Ethernet can only get about 24Mbps,it's too slow. I use  version  1.92 NDK.I have changed something in NDK what I found in wiki.Bellow：

http://processors.wiki.ti.com/wiki/index.php?title=Network_Developers_Kit_FAQ#Q:_How_to_properly_use_the_SMA_connectors_on_my_DM648EVM_board.3F

Q: How to properly use the SMA connectors on my DM648EVM board?

If you intend to use the SMA connectors without a PHY then you must perform the two modifications below:

• In the file <evmdm648init.c> lines 102-103, enable the SMA connectors by setting the two variables below to true:

use_SMA_on_port0 = TRUE;
use_SMA_on_port1 = TRUE;

This is the same as setting the parameter CPSW3G_INITPARAM_SPEED0 to 9999u in the device driver include file <cspw3g_init_cfg.h> line 160.

• In the device driver source file <cpsw3g_core.c> line 500, prevent the flag pi->TxOn to be reset by commenting out its line:

pi->TxOn = 0;

I want to know where must I  change in order to get  faster rate of Ethernet.   Thanks!