MMU & cache questions on 8240 (kernel 2.4.6)

MMU & cache questions on 8240 (kernel 2.4.6)

[Paul Chu (Accusys)]

Hello:

    Thank you for reading my questions.
    I'm porting kernel 2.4.6 to my custom 8240 board without
open firmware or any BIOS like that. I have questions at "head.S"
in the /arch/ppc/kernel directory. I cannot go back to running
unmapped after "MMU_init" and before "load_up_mmu". The
program is as follwos:
        DEBUG_OUT(0xAA)
        lis     r4,2f@h
        ori     r4,r4,2f@l
        tophys(r4,r4)
        li      r3,MSR_KERNEL & ~(MSR_IR|MSR_DR)
        FIX_SRR1(r3,r5)
        mtspr   SRR0,r4
        mtspr   SRR1,r3
        SYNC
        RFI
    2: DEBUG_OUT(0xBB)
This piece of code is from kernel and not modified at all; I'm
sure that the address caculation of "2" is correct. But I just
cannot get 0xBB at my debug port. And, when I disable
cache-enabling code, then this code can run to DEBUG_OUT(0xBB).
My cache-enabling code looks like this:
        mfspr   r3,HID0                 // enable i cache
        li      r4,0
        ori     r4,r4,(HID0_ICE|HID0_ICFI)
        or      r3,r3,r4
        mtspr   HID0,r3
        andc    r3,r3,r4
        ori     r3,r3,HID0_ICE
        mtspr   HID0,r3
        sync
        isync
        mfspr   r3,HID0                 // enable d cache
        ori     r3,r3,(HID0_DCE|HID0_DCI)
        rlwinm  r4,r3,0,22,20
        sync
        mtspr   HID0,r3
        mtspr   HID0,r4
        sync
        isync
Any advices are welcome, thank you !!
Paul Chu
Email: paulchu@accusys.com.tw


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Re: MMU & cache questions on 8240 (kernel 2.4.6)

[Paul Chu (Accusys)]

Hello:

    Thanks for those who have read my questions. Now I know
what went wrong. Because when MMU is off with cache is
on, all address seems to be cachable, and thus no data output
to my debug port. Sorry for wasting mailing list's space.

Best Regards,
Paul Chu
Email: paulchu@accusys.com.tw

----- Original Message -----
From: "Paul Chu (Accusys)" <paulchu@accusys.com.tw>
To: <linuxppc-embedded@lists.linuxppc.org>
Sent: Thursday, July 12, 2001 12:16 PM
Subject: MMU & cache questions on 8240 (kernel 2.4.6)


>
> Hello:
>
>     Thank you for reading my questions.
>     I'm porting kernel 2.4.6 to my custom 8240 board without
> open firmware or any BIOS like that. I have questions at "head.S"
> in the /arch/ppc/kernel directory. I cannot go back to running
> unmapped after "MMU_init" and before "load_up_mmu". The
> program is as follwos:
>         DEBUG_OUT(0xAA)
>         lis     r4,2f@h
>         ori     r4,r4,2f@l
>         tophys(r4,r4)
>         li      r3,MSR_KERNEL & ~(MSR_IR|MSR_DR)
>         FIX_SRR1(r3,r5)
>         mtspr   SRR0,r4
>         mtspr   SRR1,r3
>         SYNC
>         RFI
>     2: DEBUG_OUT(0xBB)
> This piece of code is from kernel and not modified at all; I'm
> sure that the address caculation of "2" is correct. But I just
> cannot get 0xBB at my debug port. And, when I disable
> cache-enabling code, then this code can run to DEBUG_OUT(0xBB).
> My cache-enabling code looks like this:
>         mfspr   r3,HID0                 // enable i cache
>         li      r4,0
>         ori     r4,r4,(HID0_ICE|HID0_ICFI)
>         or      r3,r3,r4
>         mtspr   HID0,r3
>         andc    r3,r3,r4
>         ori     r3,r3,HID0_ICE
>         mtspr   HID0,r3
>         sync
>         isync
>         mfspr   r3,HID0                 // enable d cache
>         ori     r3,r3,(HID0_DCE|HID0_DCI)
>         rlwinm  r4,r3,0,22,20
>         sync
>         mtspr   HID0,r3
>         mtspr   HID0,r4
>         sync
>         isync
> Any advices are welcome, thank you !!
> Paul Chu
> Email: paulchu@accusys.com.tw
>
>


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