Re: Raw reads from TI XIO2200(A) fail between 1800 and 2048 with RCODE 17

[Mike A. <mik...@gm...>]

On 02/08/11 17:36, Clemens Ladisch wrote:
> There were big changes, and big packets should work fine.  This looks
> more like a hardware issue.
> 
> This 1800 bytes limit is suspiciously near the default 1.7 KB AT FIFO
> DMA threshold of the XIO2200A.  Apparently, the XIO2200A cannot read the
> packet data from memory fast enough, so the packet gets corrupted.  In
> theory, this should result in the packet being retried when it has been
> completely read into the FIFO, but this does not seem to happen in your
> case.
> 
> When I did stress testing my XIO2200A with a VT6308, this worked
> correctly at all packet sizes, but this was with explicit AT transmit
> requests/responses and not physical DMA reads.
> 
> I see two possible problem sources:
> 1) the XIO2200A does not retry physical read response packets; or
> 2) the R5C832 does not correctly signal corrupted packets back to the
>    sending node.
> 
> Ricoh chips are considered cheap crap, so I'd be more suspicious about
> that one.  However, the problem might be avoided with a controller that
> does not have as agressive buffering as the XIO2200A, so you might try
> to replace either one.

Ok, thanks very much.  I've got two of the XIO2200A's, but no cable for
them, so that seems like the first step to test.  I'll try to report
back my findings, but it may take me a couple of weeks due to time
constraints.

Thanks again for you quick reply (and testing out the code to check that
it works with similar hardware)!

Mike  5:)