Re: Fwd: File system corruption

[Rogier Wolff]

On Wed, Jan 08, 2003 at 02:15:06PM +0000, Alan Cox wrote:
> On Wed, 2003-01-08 at 11:35, Paul wrote:
> > What I have found is that just after the start of a sector, usually 43 to 45 
> > bytes, 6 bytes are skipped and the sequence starts again.  This continues 
> > until the next sector starts, where the sequence corrects.  This appears to 
> > happen every 65536 bytes or some multiple of 65536.  It may skip three blocks 
> > of 65536 and then corrupt on the next block of 65536 bytes.
> 
> Ok that I'm afraid bears no resemblance to anything the software side
> does (we write in chunks but we do single PIO block transfers of each
> sector). 

After examining the resulting image, Paul has a "clock" line to his
flash device that is a bit noisy. This occasionally causes one
16-bit entity to be clocked into the device twice. 

To detect this going wrong, we could (but only as a configurable 
option), write 255 16-bit words to the device (remember this is PIO!), 
check that DRQ is still active and only then write the last word. 
(at which point DRQ should go inactive). 

				Roger. 

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