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

[Liu Dave-R63238]

> > 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.

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

Thanks, Dave