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

Josh Boyer
2011-11-03T14:43:52Z

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 would guess line 1056:

addr /= sck_xch;

addr is a u64.

> 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.
>
> Regards,
> Mauro