Problems with ST NAND512W3A nand flash

[Savin Zlobec]

Savin Zlobec wrote:
> Hi All!
> 
> I am working on a AT91RM9200 based board with ST NAND512W3A2B flash.
> Kernel version is 2.6.19.7 with patches from maxim.org.za/at91_26.html.
> Everything works perfectly, except for boot time NAND chip
> identification which fails every once in a while. NAND signature
> is 0x20 0x76, but sometimes I get 0x20 0x20. My first guess was
> timing problems, but I've double checked everything and all signals
> are inside the specs. I've also tested the chip with shorter and
> longer setup, hold and pulse times for read and write, but without
> any success. Trying different kernels didn't help either.

After some debugging I found what it looks like a silicon bug
in ST NAND512W3A2B. It looks like this particular chip doesn't
handle well the ALE and CLE transitions (no R or W) when in the
middle of READID command - other commands seem not affected.
I have the nand wired to AT91RM9200 according to the datasheet -
ALE and CLE go to A21 and A22. AT91RM9200 errata #34 states that
the address bus is continuously active, even if the address is
an internal one - so A2[12] toggle often. Sometimes it happens
that signature reading gets interrupted and if there is an
transition on A2[12] ... BOOOM - No NAND device found!!!

Regards,
savin