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Message-ID: <4BF2083B.4000303@windriver.com>
Date:   Tue, 18 May 2010 11:23:39 +0800
From:   Yang Shi <yang.shi@windriver.com>
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To:     Yang Shi <yang.shi@windriver.com>
CC:     Ralf Baechle <ralf@linux-mips.org>, linux-mips@linux-mips.org
Subject: Re: [Bug report] Got bus error when loading kernel module on SB1250
 Rev B2 board with 64 bit kernel
References: <4BED25F3.4010809@windriver.com> <20100514180211.GB32203@linux-mips.org> <4BF0B08F.1010305@windriver.com>
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Yang Shi 写道:
> Ralf Baechle 写道:
>   
>> On Fri, May 14, 2010 at 06:29:07PM +0800, Yang Shi wrote:
>>
>>   
>>     
>>> I'm running 2.6.34-rc7 mainline kernel on SB1250 (Rev B2) board. And, I
>>> use the default sb1250 kernel config (sb1250-swarm_defconfig). So, 64
>>> bit kernel is used. During kernel loading module got bus error, see
>>> below log:
>>>     
>>>       
>> Whops.  Fixes which were supposed to handle exactly this problem went
>> upstream for 2.6.34-rc3 and were tested successfully by others on their
>> systems.
>>
>> I wonder if in arch/mips/sibyte/sb1250/setup.c you can instrument
>> the function sb1250_m3_workaround_needed() and print the values of
>> soc_type, soc_pass and the retun value of that function.  Then let's take
>> it from there.
>>   
>>     
>
> See below log:
>
> Broadcom SiByte BCM1250 B2 @ 800 MHz (SB1 rev 2)
>
> And, soc_typs is 0x0 and soc_pass is 0x11, sb1250_m3_workaround_needed 
> should return 1. So, tlb refill handler should go the m3 workaround code 
> path.
>   

It seems CPU_PREFETCH caused this issue. See commit:

commit 6b4caed2ebff4ee232f227d62eb3180d0b558a31
Author: Ralf Baechle <ralf@linux-mips.org>
Date:   Wed Jan 28 17:48:40 2009 +0000

    MIPS: IP27: Switch from DMA_IP27 to DMA_COHERENT
   
    commit 0d356eaa6316cbb3e89b4607de20b2f2d0ceda25 from linux-mips
   
    The special IP27 DMA code selected by DMA_IP27 has been removed a while
    ago turning DMA_IP27 into almost a nop.  Also fixup the broken logic of
    its last users memcpy.S and memcpy-inatomic.s.
   
    Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

If undef CPU_PREFETCH for SB1250, module can be loaded correctly.

Thanks,
Yang

> Thanks,
> Yang
>
>   
>>   Ralf
>>
>>   
>>     
>
>
>
>