[U-Boot-Users] get_ram_size() returns wrong value

[Daniel Ann <ktdann@gmail.com>]

On Apr 6, 2005 9:27 PM, Jerry Van Baren <gerald.vanbaren@smiths-
> Its a memory problem.  Ultimately yes, it is a timing problem.  The
> question is where...
>   * Is it your SDRAM initialization?

Yeah looks alot like it. Previously I left bank 1 disabled. See below,
#define CFG_BANK1_ENABLE    0

I believe SDRAM is on 64bit mode, and schematics shows two chip
selects. I've sort of wrote about this prior to this email.

>   * Is it a hardware/layout problem?
>     * Are the address line lengths close to the same length?
>     * Are the data line lengths close to the same length?
>     * Is it a termination resistor problem (missing/wrong value)?
>   * Is it the SDRAM itself?

Bit hard to confirm at this stage. I guess I have to do everything I
can on the software side first. Hardware people are little reluctant
about looking up on these things.. :P

> Note that, with your printf(), you are repeatedly reading the memory at
> your boundary case address as well as changing the timing.  You are also
> doing a side-effect assignment to "addr" which gets discarded on the
> next line.
> For identifying and debugging memory problems, those are bad practices.

Thanks. I knew I was doing wrong :) Just didnt know what and why.
Didnt think my printf was a magic one :)

> My suggestion:
> 
>     for (cnt = 1; cnt < maxsize / sizeof (long); cnt <<= 1) {
>         addr = base + cnt;  /* pointer arith! */
>         val = *addr;
>         *addr = save[--i];
>         if (val != ~cnt) {
> printf("*addr %08X => %04X != %04X\n",addr,val,~cnt);
>             size = cnt * sizeof (long);
>             /* Restore the original data before leaving the function.
>              */
>             for (cnt <<= 1; cnt < maxsize / sizeof (long); cnt <<= 1) {
>                 addr  = base + cnt;
>                 *addr = save[--i];
>             }
>             return (size);
>         }
>     }

Thanks for your input. As for now, since the mistake came from
misconfiguration, I'm going to dig up on that first.

-- 
Daniel