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Subject: RE: [PATCH] usb: fsl_udc: errata - postpone freeing current dTD
From: Christoph Fritz <chf.fritz@googlemail.com>
To: Chen Peter-B29397 <B29397@freescale.com>
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Date: Mon, 21 May 2012 08:53:41 +0200
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Cc: Oliver Neukum <oneukum@suse.de>, Kukjin Kim <kgene.kim@samsung.com>,
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 Christian Hemp <c.hemp@phytec.de>, Russell King <linux@arm.linux.org.uk>,
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Hi Chen,

On Mon, 2012-05-21 at 01:05 +0000, Chen Peter-B29397 wrote:
> 
>  
> > 
> > USB controller may access a wrong address for the dTD (endpoint transfer
> > descriptor) and then hang. This happens a lot when doing tests with
> > g_ether module and iperf, a tool for measuring maximum TCP and UDP
> > bandwidth.
> > 
> > This hardware bug is explained in detail by errata number 2858 for i.MX23:
> > http://cache.freescale.com/files/dsp/doc/errata/IMX23CE.pdf
> > 
> 
> Does this patch fix your problem?

yes, it does! :-)

> > +#if defined CONFIG_ARCH_MX51 || defined CONFIG_SOC_IMX35
> > +#define POSTPONE_FREE_LAST_DTD
> > +#else
> > +#undef POSTPONE_FREE_LAST_DTD
> > +#endif
> > +
> All i.mx SoC has this problem, if PowerPC also has this problem, you can 
> delete #if defined. Else, you can define it for all i.mx SoC 
> (CONFIG_ARCH_MXC | CONFIG_ARCH_MXS)

I was unsure about this too. I can only test imx35. And mx51 was defined
in your tree. So these two should be defined anyway.

Marvell doesn't use any defines in mv_udc_core for their fix, so I would
be fine without ifdefs too. Any objections? Please see next mail with
patch v2.


Thanks,
 -- Christoph