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Date: Wed, 9 May 2012 07:38:27 +0200
From: Christoph Fritz <chf.fritz@googlemail.com>
To: Chen Peter-B29397 <B29397@freescale.com>, Chao Xie <cxie4@marvell.com>
Subject: Re: [RFC] [PATCH] usb: gadget: fix dtd dma confusion
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Hi Peter,

 thanks you for your help.

On Wed, May 09, 2012 at 02:11:56AM +0000, Chen Peter-B29397 wrote:
> 
>  
> > >
> > > after a while of testing and searching I can come up with a patch
> > > that fixes g_ether <-> iperf for fsl_udc on ARM i.MX35.
> > >
> > > The sad part is that this kind of fix is already implemented for
> > > marvell mv_udc driver since last year but still _not_ in the ~15
> > > other *udc.c drivers.
> > >
>  
> It is a controller limitation (bug?) for chipidea controller when using
> dtd list to handle multi-dtds situation. The controller will read dtd's
> next pointer after this dtd's active bit has already been cleared.
> 
> Freescale has an errata for this problem's description and solution.
> http://cache.freescale.com/files/dsp/doc/errata/IMX23CE.pdf
> See 2858

I'm hacking here an i.MX35 not an i.MX23. So I already had a look at its
errata sheet http://cache.freescale.com/files/dsp/doc/errata/IMX35CE.pdf
but didn't find a similar "limitation" as you now pointed out by errata
number 2858 for i.MX23.

What about the fix for mv_udc, shouldn't they have a similar
"limitation"? How do you explain?
Or maybe someone from Marvell has an answer?


Thanks,
 -- Christoph