[U-Boot-Users] Cache issue on MPC8xx

[Jerry Van Baren <gerald.vanbaren@smiths-aerospace.com>]

Qichen Huang wrote:
> On 8/24/06, Wolfgang Denk <wd@denx.de> wrote:
>> In message <b4ebaa9d0608240832i212b01aey4f?e1362002756833@mail.gmail.com> you wrote:
>>> I did so, but still couldn't get D-Cache enabled.
>> Then you did something wrong.
> I have been trapped in this problem for a long time. Could you tell me
> some more details. Thanks.
> 
> What I did is:
>  - set msr to 0.
>  - disable D-cache
>  - enable D-cache  <-- and it crashes here.

This is impossibly vague.  There are many reasons for "it crashes here." 
including that it quite likely doesn't crash there.

* Are you running with instruction cache enabled?  If so, your memory 
controller is probably configured OK.  If not, it is very possible that 
your memory controller isn't handling bursts properly.

* How do you know it crashes there?  When you turn on data cache, all of 
your peripherals, including blinkin' LEDs and your UART, get cached so 
you won't see anything unless you have set up BAT registers or the MMU 
to control the data cache such that your peripherals are NOT cached.

* If you have set up the BAT and/or the MMU, did you do it correctly?

* Did you FOLLOW THE INSTRUCTIONS in the user's guide on the proper 
sequence when messing with the MSR register?  Really weird things happen 
if you don't (or so they tell me ;-).

> What is the correct way?

That is the nutshell correct way.  There are a lot of details that have 
to be done right before it works, however.  There is a devil hiding in 
each and every detail.

> Qichen

HTH,
gvb