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

[Jens Gehrlein]

Liu Dave-R63238 schrieb:
>>> 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).  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.
>>
>> 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.
> 
> It needs case by case.
> 
> * 83xx, the whole d-cache is locked
> If you need generate bursts on DRAM interface, you have to change to
> way locked. Otherwise, you can use the DMA to generate burst.

Good idea.

> * 85xx, half of d-cache is locked.
> it is possible to generate the burst at 85xx.
> Try to use dcbf....

Thank you for the hints.

Kind regards,
Jens