Re: [Bug report] Got bus error when loading kernel module on SB1250 Rev B2 board with 64 bit kernel

[Yang Shi <yang.shi@windriver.com>]

Yang Shi 写道:
> 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>
>   

This patch did below fix:

-#if !defined(CONFIG_DMA_COHERENT) || !defined(CONFIG_DMA_IP27)
+#ifdef CONFIG_DMA_NONCOHERENT
 #undef CONFIG_CPU_HAS_PREFETCH

Before the fix, CONFIG_DMA_IP27 is undefined for all of boards except 
IP27, so CONFIG_CPU_HAS_PREFETCH is undefined always.

Thanks,
Yang

> If undef CPU_PREFETCH for SB1250, module can be loaded correctly.
>
> Thanks,
> Yang
>
>   
>> Thanks,
>> Yang
>>
>>   
>>     
>>>   Ralf
>>>
>>>   
>>>     
>>>       
>>
>>   
>>     
>
>
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