[U-Boot] ppc: using d-cache for C stack and as cache at the same time?

[Jens Gehrlein]

Dear Wolfgang Denk,

Wolfgang Denk schrieb:
> Dear Jens Gehrlein,
> 
> In message <49D323E5.9080100 at tqs.de> you wrote:
>> AFAIK, while running from flash, u-boot uses (part of) d-cache on some
>> platforms for the C stack. I think, it's on MPC83xx and MPC85xx?
>>
>> Does anybody know, if I can use the remaining part of the d-cache
>> as normal d-cache, e.g. to generate bursts on the SDRAM interface
>> while testing the RAM?
> 
> On which platform?
> 
> Note that implementing a memory test  that  actually  triggers  burst
> mode  accesses  is really, really tricky. You probably do NOT want to
> do this while running from flash  (i.  e.  from  a  very  restrictive
> envrionment). 

Why not? Of course, it's only possible if I can use a part of the
D-Cache as C stack (or another internal RAM if available). This must
be separately checked for each processor.

> You  might want to have a look at examples/test_burst*
> but note that this code was written for a MPC8xx system,  so  changes
> will be required for 83xx or 85xx.

Thank you for the hint. I'll have a look.

> Also note that a much more reliable test for burst mode errors is to
> boot Linux with root file system over NFS and then compile the Linux
> kernel on the target.

I agree.

Kind regards,
Jens