RE: [RFC] gadget ethernet dma align fix

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> -----Original Message-----
> From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb-
> owner@xxxxxxxxxxxxxxx] On Behalf Of Gupta, Ajay Kumar
> Sent: Tuesday, January 12, 2010 7:05 PM
> To: Pandita, Vikram; Matthieu CASTET
> Cc: matthieu castet; linux-usb@xxxxxxxxxxxxxxx; Alan Stern
> Subject: RE: [RFC] gadget ethernet dma align fix
> 
> 
> 
> > -----Original Message-----
> > From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb-
> > owner@xxxxxxxxxxxxxxx] On Behalf Of Pandita, Vikram
> > Sent: Saturday, January 09, 2010 4:21 AM
> > To: Matthieu CASTET
> > Cc: matthieu castet; linux-usb@xxxxxxxxxxxxxxx; Alan Stern
> > Subject: RE: [RFC] gadget ethernet dma align fix
> >
> >
> >
> > >-----Original Message-----
> > >From: Matthieu CASTET [mailto:matthieu.castet@xxxxxxxxxx]
> > >Sent: Friday, January 08, 2010 10:15 AM
> > >To: Pandita, Vikram
> > >Cc: matthieu castet; linux-usb@xxxxxxxxxxxxxxx; Alan Stern
> > >Subject: Re: [RFC] gadget ethernet dma align fix
> > >
> > >Hi,
> > >
> > >Pandita, Vikram a écrit :
> > >> Matthieu
> > >>
> > >>> -----Original Message-----
> > >>> From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb-
> > owner@xxxxxxxxxxxxxxx] On Behalf Of
> > >matthieu
> > >>> castet
> > >>> Sent: Wednesday, December 23, 2009 2:11 PM
> > >>> To: linux-usb@xxxxxxxxxxxxxxx
> > >>> Cc: Alan Stern
> > >>> Subject: [RFC] gadget ethernet dma align fix
> > >>>
> > >>> Hi,
> > >>>
> > >>> I attach a patch that should allow to use gadget ethernet with
> driver
> > >>> not supporting dma on unaligned address.
> > >>>
> > >>> This is untested on real hardware.
> > >>
> > >> Gave a first round of test on real hardware.
> > >>
> > >> 1) patch did not compile
> > >> 	a) missing ;
> > >> 	b) a typecast was needed like: ((unsigned long)skb->data & 3)
> > >> 	c) WARN_ON() getting hit multiple times, thereby generating un-
> > managable amount of logs: so
> > >disable WARN_ON()
> > >That's not normal. We drop all these packets. That should explain why
> > >"Ping from device side hangs" is not working.
> > >
> > >What's the value of skb_headroom in this case.
> > >May be the check should be
> > >if ( (skb_headroom(skb) < ((unsigned long)skb->data & 3) ))
> >
> > Yes that's the check that was needed.
> > So now I have working v3 of the patch(attached) with:
> > 	a) added more comments
> > 	b) tx alignment added a gadget_dma32() check
> >
> > This works perfectly fine for ping from both sides (host/device).
> 
> I also tested it on OMAP3730 EVM (based on 3630) and observed that
> Basic ping works (64 byte) but ping for packet size 2K fails.
> 
> I tried flood ping and that also is failing.

This failure was with Linux host (driver in CDC mode) buy I can see
Successful ping with Windows XP pc for packets size upto 65500.

-Ajay
> 
> -Ajay
> >
> > Maybe we finally have a solution.
> > Can we get a round of review on usb list?
> >
> > Regards,
> > Vikram
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