[alsa-devel] [PATCH] ASoC: prevent compilers from optimising pll calculation into __aeabi__uldivmod

[Takashi Iwai]

At Wed, 27 Apr 2011 16:24:44 +0800,
Barry Song wrote:
> 
> 2011/4/27 Takashi Iwai <tiwai at suse.de>:
> > At Wed, 27 Apr 2011 00:27:32 -0700,
> > Barry Song wrote:
> >>
> >> From: Barry Song <21cnbao at gmail.com>
> >>
> >> The newest compiliers can optimize pll calculation in several codecs into __aeabi__uldivmod which doesn't exist in kernel.
> >> Then the link will fail:
> >> ERROR: "__aeabi_uldivmod" [sound/soc/codecs/snd-soc-wm8974.ko] undefined!
> >> ERROR: "__aeabi_uldivmod" [sound/soc/codecs/snd-soc-wm8940.ko] undefined!
> >> ERROR: "__aeabi_uldivmod" [sound/soc/codecs/snd-soc-wm8510.ko] undefined!
> >> This patch prevent the optimizaton by insert ASM.
> >
> > Don't do this in the low driver level.  If any, we should fix do_div()
> > instead.
> 
> do_div is just a macro, it has no problem by itself.

It has a problem by itself because it's a macro with a side-effect :)

Could we put an asm to do_div() itself?  The asm statement can be
defined depending on the compiler version.

> only while
> working together with other more codes before do_div, gcc can make
> some codes merging and cause problems.
> 
> if do_div is a function, we'd just fix it.

Better to ask this in LKML, then.


thanks,

Takashi