[openfirmware] OFW x86 MMU Setup

Mitch Bradley wmb at laptop.org
Thu Jun 19 19:05:37 CEST 2008


Andrea wrote:
>
>
> Mitch Bradley wrote:
>> See http://wiki.laptop.org/go/Forth_Lesson_17
>>
>
> Thanks for the Lesson Mitch!
>
> I successfully enabled MMU but there is still some other problem, I 
> think at lower level that this..
> At address 0xFFAC0000 (physical or virtual it's the same.. I choose 
> phys=virt for ease) I should see my second flash (with IDSEL=1) but I 
> still see the first one (which is not a real LPC flash but an LPC dongle)
>
> It's not a problem of physical address conflict (on LPC bus) due the 
> fact that I can see the right data at system reset (with a JTAG 
> debugger, as previuosly told).
> With the same JTAG debugger, if I break the system when OFW is already 
> initialized, I have the same problem as above (at physical address 
> 0xFFAC0000 I see the LPC dongle memory)
>
> It seems that something at lower software level (some msr setup?) 
> "maps" 0xFFAC0000 somewhere else on LPC bus ('still don't know where.. 
> I will investigate..)
>
> Can you tell me where this kind of mappings (if any, of course) are 
> done in OFW? (I thinks it's not strictly OFW dependent but only 
> platform dependent.. but it will be usefull anyway to know where to 
> look inside OFW for the required changes)

The MSR setup is done in two places:
  lxdevel/romreset.bth lines 89-103
  lxdevel/msrinit.fth  - table at beginning of file, routine to process 
that table at line 262

The MSRs setup in romreset.bth is necessary for early startup, to get 
the memory working.  The rest of them can be deferred until later.


>
> Can you also tell me where the MMU mapping of the first flash 
> (0xFFBC0000) is done? (maybe I can add my mmu initialization in a 
> better place..)

I'm not sure.  I thought the LPC FLASH was at fff0.0000.
>
> TIA and best regards,
>




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