RE: [PATCH 2/6] usb: gadget: mv_udc: disable HW zlt for ep0

[Neil Zhang]

> -----Original Message-----
> From: Peter Chen [mailto:Peter.Chen@xxxxxxxxxxxxx]
> Sent: 2014年2月25日 13:15
> To: Neil Zhang
> Cc: balbi@xxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; linux-usb@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx
> Subject: RE: [PATCH 2/6] usb: gadget: mv_udc: disable HW zlt for ep0
> 
> 
> 
> 
> > > On Mon, Feb 24, 2014 at 04:03:12PM +0800, Neil Zhang wrote:
> > > > Hardware zlt will try to send the zero length packet automatically
> > > > when the data transferd is multiple times of max packet, this will
> > > > cause issues on Windows.
> > > > So let's disable HW zlt by default.
> > >
> > > Would you have description that what kinds of issue on Windows if
> > > zlt is is selected?
> > >
> >
> > Enumeration will fail.
> >
> 
> What causes enumeration fail, why it does not occur before?
> 
A unexpected zero packet cause enumeration fail.
It's not easy that the descriptor is actually 1024 bytes, so not easy to be found.

> Peter

Best Regards,
Neil Zhang

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