[Skyeye-developer] switch off MMU on ARM920 or ARM926

[sergey bryukov]

1.  MMU initialization should be occurred in function mmu_init from the file
armmmu.c
2.  mmu_init() should be invoked  fore any ARM core even it hasn't MMU in
general.

mmu_init():
switch (state->cpu->cpu_val & state->cpu->cpu_mask) {
    case 0x41807200:    //arm720t
    case 0x41007700:    //arm7tdmi

    case 0x41007100:    //arm7100
                fprintf (stderr, "SKYEYE: use arm7100 mmu ops\n");
                state->mmu.ops = arm7100_mmu_ops;
                break;
}

>From the code above  for arm7tdmi mmu of arm7100 is appealed. ARM7tdmi
hasn't MMU but it has MCR, MRC instructions are declared in armmmu.c

My question is should I present dummy mmu for new core to support MRC, MCR
instructions ?


On Jan 30, 2008 11:31 PM, Michael. Kang <blackfin.kang at gmail.com> wrote:

> On Jan 30, 2008 8:59 AM, sergey bryukov <sb.subscribe at gmail.com> wrote:
> > As I understand, there is core hierarchy chart in ARM family like below:
> >
> > |- ARMv5TE
> > |                  |- ARM9E-S
> > |                                  |-ARM966E-S
> >  |
> > |- ARMv5TEJ
> > |                 |-  ARM9EJ-S
> > |                                     |- ARM926EJ-S
> > |
> > |
> > |- ARMv4T
> > |              |- ARM9TDMI
> > |                                   |- ARM920T
> >
> >  Two processors of them are presented in the Skyeye -  ARM926EJ-S and
> > ARM920T.
> > ARM926EJ-S is the most  closed to ARM966E-S. And I don't know what means
> > '-S' in architecture name.
> >
> > comparison table:
> >
> > ARM966E-S
> > ARM926EJ-S
> > ARM9E-S integer core
> ARM9EJ-S
> > integer core
> > simple fixed memory map                                          MMU
> >
> > features for efficient execution of Java byte codes
> >
> > Harvard cached architecture  4KB or 128KB
> >
> >
> > 1. If weren't use Java support  functionality  of  926EJ-S, instruction
> set
> > of both CPU should be the same.
> >
> > 2. For   926EJ-S  the caches, Tightly-Coupled Memories (TCMs), Memory
> > Management Unit (MMU), and most other system options are controlled
> using
> > CP15 registers. It should be possible switch off all of them and get
> 966E-S
> > in general.
> >
> > Does it look like true?
> maybe, I have not read these manual in every detail.
> >
> > In the Skyeye's sources there is ns9750_mach_init() - it presents
> ARM926EJS
> > based CPU.
> > To initialize arm emulator ARMul_SelectProcessor (state, ARM_v5_Prop |
> > ARM_v5e_Prop) function should be invoked for ARM926EJS.
> >  Does the same parameters should be used in case of any ARMv5E core
> based
> > target?
> >
> > Could you refer me how-to add new arm core to the skyeye?
> According to my understanding, you should add a MMU implementation in
> arch/arm/common/mmu/ , just like other core. Then add some entry in
> arch/arm/common/armmmu.c . Anyway, you can try it firstly.
> >
> > Thanks,
> > Sergey.
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > On Jan 29, 2008 4:33 PM, Michael. Kang <blackfin.kang at gmail.com>
> wrote:
> > >
> > > > Yes,You can  run some nommu applications or RTOS with MMU off. But I
> > > > donot know if ARM920T with MMU off has same behaviour with ATM966E.
> > > > Except MMU , is there any other difference between ARM966E and
> > > > ARM920T??
> > > >
> > > > Thanks
> > > > MK
> > > >
> > > >
> > > >
> > > > On 1/29/08, sergey bryukov <sb.subscribe at gmail.com> wrote:
> > > > > Hello Kang!!!
> > > > > I've been spending some time to add new SOC to skyeye and I found
> > skyeye is
> > > > > grate for quick SoC design .
> > > > > Thanks to project attenders!!!!
> > > > >
> > > > > Is it possible to switch off MMU during ARM920 emulation  by
> > configuration
> > > > > register CP15  to present cores like ARM966E?
> > > > >  In another words, is it possible invoke ARM9 not MMU  RTOS
> enviroment
> > under
> > > > > Skyeye?
> > > > >
> > > > > Thanks.
> > > > >
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