Re: sb_edac 32-bit compile fail due to 64-bit divide

Mauro Carvalho Chehab
2011-11-03T17:20:19Z

Em 03-11-2011 12:43, Josh Boyer escreveu:
> On Thu, Nov 03, 2011 at 12:32:31PM -0200, Mauro Carvalho Chehab wrote:
>> Em 03-11-2011 12:07, Josh Boyer escreveu:
>>> Hi,
>>>
>>> It seems the newly added EDAC driver for SandyBridge won't build on
>>> 32-bit x86 because of a 64-bit divide somewhere:
>>>
>>> drivers/edac/sb_edac.c: In function 'get_memory_error_data':
>>> drivers/edac/sb_edac.c:861:2: warning: left shift count >= width of type
>>> [enabled by default]
>>> <snip>
>>> ERROR: "__udivdi3" [drivers/edac/sb_edac.ko] undefined!
>>> make[1]: *** [__modpost] Error 1
>>> make: *** [modules] Error 2
>>>
>>> You can find the full build log here:
>>>
>>> http://koji.fedoraproject.org/koji/getfile?taskID=3482579&name=build.log
>>>
>>> Before I go digging into where this is done and what to do about it, I
>>> do want to confirm that it is supposed to work on a 32-bit kernel,
>>> correct?
>>
>> Thanks for pointing it!
>>
>> Well, I didn't test it on a 32-bit kernel. It should work through.
>>
>> It is probably due to those debug lines:
>> debugf0("CH#%d RIR#%d INTL#%d, offset %Lu.%03Lu GB (0x%016Lx), tgt: %d, reg=0x%08x\n",
>> i, j, k,
>> tmp_mb / 1000, tmp_mb % 1000,
>> ((u64)tmp_mb) << 20L,
>> (u32)RIR_RNK_TGT(reg),
>> reg);
>> (same kind of calculus is recurrent at the driver)
>
> All of that should basically not exist in this build because the debugf*
> macros depend on CONFIG_EDAC_DEBUG, which isn't set in this build. The
> problem seems to be somewhere else.

I strongly recommend you to enable EDAC_DEBUG if you're building this driver. This
driver is experimental, and it may be blaming the wrong memory DIMMs, as Sandy
Bridge bios allows setting a large myriad of configurations. Among them, only one
were actually tested.

>
> I would guess line 1056:
>
> addr /= sck_xch;
>
> addr is a u64.

Ok.

Well, a patch fixing it should be done with debug enabled, to get all cases.

>> Maybe the easiest way would be to write a function that would call do_div() internally,
>> and output a string with something similar to:
>>
>> sprintf(msg, "%Lu.%03Lu GB", tmp_mb / 1000, tmp_mb % 1000);
>>
>> Of course, an interim fix would be to make it depend on CONFIG_64BIT or CONFIG_X86_64.
>
> That would work I guess. It's up to you.

I prefer a patch fixing the issue. Not sure if I'll have time to work in it today,
as I'm stuck with the second part of media patches for 3.2.

>>
>> Regards,
>> Mauro
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