You have to identify problem caused by 
SDIO host controller or wifi driver.

If driver is working well in x86 with Roch SDIO, that means wifi driver is ok. 

You have to find out
1. SDIO interface if using Interrupt or PIO
2. 1 bit or 4 bit
3. TI BSP SDIO controller 

--- On Wed, 6/13/12, Andreas Kemnade <andreas@kemnade.info> wrote:

From: Andreas Kemnade <andreas@kemnade.info>
Subject: Re: poor performance with W2CBW003 (Marvell 8686)
To: "hong zhang" <redacted>
Cc: "Dan Williams" <redacted>, linux-wireless@vger.kernel.org, dsd@laptop.org, libertas-dev@lists.infradead.org
Date: Wednesday, June 13, 2012, 12:42 PM
Hi,

On Wed, 13 Jun 2012 10:06:54 -0700 (PDT)
hong zhang [off-list ref]
wrote:

quoted

quoted

4 bit is supported.
The hardware does not impose unresolvable

limitations, the

quoted

quoted

2.6.32 kernel
gives high performance. But since that kernel is

not

quoted

quoted

mainstream, it is
very hard to find out which patch gives the

slowdown. git

quoted

quoted

bisect
is not very useful in that situation.
SD memory card reading speed is always ok (on

another of the

quoted

quoted

integrated
sd host controllers).

Have you tested receive throughput? Any difference

between TX and Rx throughput? 

quoted

I tested both.
No significant difference with 3.x.

Greetings
Andreas Kemnade