Re: MPC5200 ethernet communication stops unexpected

["David Kanceruk" <david.kanceruk@gmail.com>]

Hello Hans,

     There sure seems to be strange behavior in the BestComm unit. Our
problem was always with the first byte or the 63rd byte on a buffer of
102 bytes.

     Did you use a value of (1<<16) for the BSDIS bit? We also do a
ioremap when setting a pointer to the xlb.

Dave

On 5/15/07, Hans Thielemans <Hans.Thielemans@metris.com> wrote:
> Hello David,
>
> In this case, I am flushing cache. And overall, these are empty packets
> sent which are never changed.
> The cpu creates this once and then this is always reused. It is received
> maybe 100000 times correct and
> then suddenly I see an error in the last word.
>
> I also tried playing with the BSDIS and PLDIS bits, and with the bus
> priorities. This influences the error rate,
> but it is never really gone.
>
> As a hack I have now added an extra word after the packet, and have the
> receiver ignore it. This seems to help,
> but I don't like it.
>
> Regards
>
> Hans
>
> -----Original Message-----
> From: David Kanceruk [mailto:david.kanceruk@gmail.com]
> Sent: dinsdag 15 mei 2007 17:04
> To: Hans Thielemans
> Cc: linuxppc-embedded@ozlabs.org
> Subject: Re: MPC5200 ethernet communication stops unexpected
>
> Hello Hans,
>
>      Our problem was with the FEC sending data with one or two incorrect
> bytes when we switched from the MPC5200 to the MPC5200B. The byte
> positions were always the same. The socket buffer has the correct data
> before and after the DMA engine runs but the FEC TxFIFO does not always
> match.
>
> One solution to our problem was to make the following call prior to
> starting the DMA:
>
> flush_dcache_range((unsigned long)skb->data, (unsigned long)skb->data
> + skb->len);
>
> The other solution was to set the BSDIS bit in the XLB config register
> during initialization as follows:
>
>   xlb = (struct mpc52xx_xlb *)MPC5xxx_XLB;
>   out_be32(&xlb->config,  in_be32(&xlb->config) |
> MPC52xx_XLB_CFG_BSDIS);
>
> Either solution works for us. The BSDIS bit is a new feature in the
> MPC5200B. The MPC5200 did not have this bit.
>
> According to the Freescale documentation, (Application note AN3045, for
> instance) setting this bit is supposed to "disable" BestComm bus
> snooping. However, I have reason to believe the documentation is in
> error. Everything I have observed seems to indicate that in the MPC5200
> BestComm bus snooping was always enabled or enabled via some other
> means. In the MPC5200B it appears to be "disabled" at reset (not
> "enabled" as the documentation states). This is why flushing the cache
> manually is one solution. Since setting the BSDIS bit also fixes the
> problem, it suggests that this actually "enables" BestComm bus snooping
> instead of disabling it. In my mind, it could all boil down to a simple
> documentation error.
>
> Perhaps you are also experiencing a caching problem.
>
> Best regards,
>
> David Kanceruk
>
> On 5/15/07, Hans Thielemans <hans.thielemans@metris.com> wrote:
> > Hi David,
> >
> > I have a similar problem. I use the PSC for communication to a DSP.
> > With the MPC5200 this has always worked. Now we got boards with the
> > MCP5200B in place.
> >
> > The bestcomm dma seems to miss bits, bytes in the last word (32bit) of
>
> > a dma block. Mostly it is one byte which becomes 0. The blocks are 256
>
> > bytes and written/read by 32 bits.
> > The behavior is influenced by cpu activity, bus priorities. So far I
> > found no settings which have never errors.
> >
> > Did you have any further progress?
> >
> > Regards
> >
> > Hans Thielemans
> >
>
>
>
> --
> David Kanceruk
>
> "The generation of random numbers is far too important to be left to
> chance."
>
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-- 
David Kanceruk

"The generation of random numbers is far too important to be left to chance."