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

[Barry Song]

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. 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.
>
>
> thanks,
>
> Takashi
>
>>
>> Signed-off-by: Barry Song <21cnbao at gmail.com>
>> Cc: Zhiwu Song <zhiwu.song at csr.com>
>> Cc: Binghua Duan <binghua.duan at csr.com>
>> ---
>>  sound/soc/codecs/wm8510.c |    6 ++++++
>>  sound/soc/codecs/wm8940.c |    6 ++++++
>>  sound/soc/codecs/wm8974.c |    6 ++++++
>>  3 files changed, 18 insertions(+), 0 deletions(-)
>>
>> diff --git a/sound/soc/codecs/wm8510.c b/sound/soc/codecs/wm8510.c
>> index db0dced..a636b15 100644
>> --- a/sound/soc/codecs/wm8510.c
>> +++ b/sound/soc/codecs/wm8510.c
>> @@ -258,6 +258,12 @@ static void pll_factors(unsigned int target, unsigned int source)
>>       Nmod = target % source;
>>       Kpart = FIXED_PLL_SIZE * (long long)Nmod;
>>
>> +     /*
>> +      * The following asm() prevents the compiler from optimising
>> +      * into a standard EABI function __aeabi__uldivmod()
>> +      */
>> +     asm("" : "+r"(source));
>> +
>>       do_div(Kpart, source);
>>
>>       K = Kpart & 0xFFFFFFFF;
>> diff --git a/sound/soc/codecs/wm8940.c b/sound/soc/codecs/wm8940.c
>> index 25580e3..f6148af 100644
>> --- a/sound/soc/codecs/wm8940.c
>> +++ b/sound/soc/codecs/wm8940.c
>> @@ -520,6 +520,12 @@ static void pll_factors(unsigned int target, unsigned int source)
>>       Nmod = target % source;
>>       Kpart = FIXED_PLL_SIZE * (long long)Nmod;
>>
>> +     /*
>> +      * The following asm() prevents the compiler from optimising
>> +      * into a standard EABI function __aeabi__uldivmod()
>> +      */
>> +     asm("" : "+r"(source));
>> +
>>       do_div(Kpart, source);
>>
>>       K = Kpart & 0xFFFFFFFF;
>> diff --git a/sound/soc/codecs/wm8974.c b/sound/soc/codecs/wm8974.c
>> index ca646a8..c9036d9 100644
>> --- a/sound/soc/codecs/wm8974.c
>> +++ b/sound/soc/codecs/wm8974.c
>> @@ -317,6 +317,12 @@ static void pll_factors(struct pll_ *pll_div,
>>       Nmod = target % source;
>>       Kpart = FIXED_PLL_SIZE * (long long)Nmod;
>>
>> +     /*
>> +      * The following asm() prevents the compiler from optimising
>> +      * into a standard EABI function __aeabi__uldivmod()
>> +      */
>> +     asm("" : "+r"(source));
>> +
>>       do_div(Kpart, source);
>>
>>       K = Kpart & 0xFFFFFFFF;
>> --
>> 1.7.1
>>
>>
>>
>> Member of the CSR plc group of companies. CSR plc registered in England and Wales, registered number 4187346, registered office Churchill House, Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ, United Kingdom
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>