[U-Boot-Users] PPC: How to access RAM location 0x0 (unmapped) ?

[Christopher E Cordahi]

"KokHow Teh" <KokHow.Teh at marconi.com> wrote on 2005-04-28 03:12:14:

> The reason of the crash was because I put get_ram_size() before the sdram
> controller was initialized. I don't know how it works in sbc8240 but this
> is what I get in tqm8260:

> /* We must be able to test a location outsize the maximum legal size
> * to find out THAT we are outside; but this address still has to be
> * mapped by the controller. That means, that the initial mapping has
> * to be (at least) twice as large as the maximum expected size.
> */

The initial mapping does not have to be (at least) twice as large as
the maximum expected size.  This comment may be a result of an old
bug in get_ram_size() which performed a test at base + max_size.
The function now stops testing when it has found max_size bytes.

Of coarse the controller still has to be initialized and map max_size
bytes before calling the function.

Chris