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

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

[Barry Song]

From: Barry Song <21cnbao@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.

Signed-off-by: Barry Song <21cnbao@gmail.com>
Cc: Zhiwu Song <zhiwu.song@csr.com>
Cc: Binghua Duan <binghua.duan@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

Re: [PATCH] ASoC: prevent compilers from optimising pll calculation into __aeabi__uldivmod

[Takashi Iwai]

At Wed, 27 Apr 2011 00:27:32 -0700,
Barry Song wrote:
> 
> From: Barry Song <21cnbao@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.


thanks,

Takashi

> 
> Signed-off-by: Barry Song <21cnbao@gmail.com>
> Cc: Zhiwu Song <zhiwu.song@csr.com>
> Cc: Binghua Duan <binghua.duan@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
> _______________________________________________
> Alsa-devel mailing list
> Alsa-devel@alsa-project.org
> http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
> 

Re: [PATCH] ASoC: prevent compilers from optimising pll calculation into __aeabi__uldivmod

[Barry Song]

2011/4/27 Takashi Iwai <tiwai@suse.de>:
> At Wed, 27 Apr 2011 00:27:32 -0700,
> Barry Song wrote:
>>
>> From: Barry Song <21cnbao@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@gmail.com>
>> Cc: Zhiwu Song <zhiwu.song@csr.com>
>> Cc: Binghua Duan <binghua.duan@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
>> _______________________________________________
>> Alsa-devel mailing list
>> Alsa-devel@alsa-project.org
>> http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
>>
>
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Re: [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@suse.de>:
> > At Wed, 27 Apr 2011 00:27:32 -0700,
> > Barry Song wrote:
> >>
> >> From: Barry Song <21cnbao@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
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Re: [PATCH] ASoC: prevent compilers from optimising pll calculation into __aeabi__uldivmod

[Barry Song]

2011/4/27 Takashi Iwai <tiwai@suse.de>:
> At Wed, 27 Apr 2011 16:24:44 +0800,
> Barry Song wrote:
>>
>> 2011/4/27 Takashi Iwai <tiwai@suse.de>:
>> > At Wed, 27 Apr 2011 00:27:32 -0700,
>> > Barry Song wrote:
>> >>
>> >> From: Barry Song <21cnbao@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.

I must have been delaying a little from gcc.  Michael Hope has thought
it as a gcc bug on 26 April,2011at:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48783

Marking pll_factors() as noinline or putting asm("" : "+r"(source)); before the
call to do_div() works around the problem.

>
>
> thanks,
>
> Takashi
>
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Re: [PATCH] ASoC: prevent compilers from optimising pll calculation into __aeabi__uldivmod

[Mark Brown]

On Wed, Apr 27, 2011 at 04:50:12PM +0800, Barry Song wrote:

> Marking pll_factors() as noinline or putting asm("" : "+r"(source)); before the
> call to do_div() works around the problem.

If we do have to do something in the callers rather than in do_div() the
annotation seems substantially more taseful than inserting a random asm
into the code.

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

[Barry Song]

2011/4/27 Mark Brown <broonie-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org>
>
> On Wed, Apr 27, 2011 at 04:50:12PM +0800, Barry Song wrote:
>
> > Marking pll_factors() as noinline or putting asm("" : "+r"(source)); before the
> > call to do_div() works around the problem.
>
> If we do have to do something in the callers rather than in do_div() the
> annotation seems substantially more taseful than inserting a random asm
> into the code.
I agree. for this patch which will not be applied, people can just get
information about how to workaround the gcc issue while they have the
same problem. google can find there are other people who failed to
compile wm8974 module too. eg.
http://irclogs.ubuntu.com/2010/03/30/%23ubuntu-arm.txt

Andrew Stubbs, Michael Hope in Linaro's toolchain team are working
hard on this gcc issue. there have been many update today:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48783

Re: [PATCH] ASoC: prevent compilers from optimising pll calculation into __aeabi__uldivmod

[Mark Brown]

On Wed, Apr 27, 2011 at 11:00:18PM +0800, Barry Song wrote:
> 2011/4/27 Mark Brown <broonie@opensource.wolfsonmicro.com>

> > If we do have to do something in the callers rather than in do_div() the
> > annotation seems substantially more taseful than inserting a random asm
> > into the code.

> I agree. for this patch which will not be applied, people can just get
> information about how to workaround the gcc issue while they have the
> same problem. google can find there are other people who failed to
> compile wm8974 module too. eg.
> http://irclogs.ubuntu.com/2010/03/30/%23ubuntu-arm.txt

> Andrew Stubbs, Michael Hope in Linaro's toolchain team are working
> hard on this gcc issue. there have been many update today:
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48783

Is this just some Linaro toolchain that has the issue rather than a
vanilla GCC release?  If so and they fix the compiler bug it doesn't
seem terribly useful to bodge it in mainline.

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

[Barry Song]

2011/4/27 Mark Brown <broonie@opensource.wolfsonmicro.com>:
> On Wed, Apr 27, 2011 at 11:00:18PM +0800, Barry Song wrote:
>> 2011/4/27 Mark Brown <broonie@opensource.wolfsonmicro.com>
>
>> > If we do have to do something in the callers rather than in do_div() the
>> > annotation seems substantially more taseful than inserting a random asm
>> > into the code.
>
>> I agree. for this patch which will not be applied, people can just get
>> information about how to workaround the gcc issue while they have the
>> same problem. google can find there are other people who failed to
>> compile wm8974 module too. eg.
>> http://irclogs.ubuntu.com/2010/03/30/%23ubuntu-arm.txt
>
>> Andrew Stubbs, Michael Hope in Linaro's toolchain team are working
>> hard on this gcc issue. there have been many update today:
>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48783
>
> Is this just some Linaro toolchain that has the issue rather than a
> vanilla GCC release?  If so and they fix the compiler bug it doesn't
> seem terribly useful to bodge it in mainline.
>

i am guessing it is a generic gcc issue since Michael posted it at
http://gcc.gnu.org/bugzilla not Linaro's Launchpad. not sure :-)

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

[Barry Song]

2011/4/27 Barry Song <21cnbao@gmail.com>:
> 2011/4/27 Mark Brown <broonie@opensource.wolfsonmicro.com>:
>> On Wed, Apr 27, 2011 at 11:00:18PM +0800, Barry Song wrote:
>>> 2011/4/27 Mark Brown <broonie@opensource.wolfsonmicro.com>
>>
>>> > If we do have to do something in the callers rather than in do_div() the
>>> > annotation seems substantially more taseful than inserting a random asm
>>> > into the code.
>>
>>> I agree. for this patch which will not be applied, people can just get
>>> information about how to workaround the gcc issue while they have the
>>> same problem. google can find there are other people who failed to
>>> compile wm8974 module too. eg.
>>> http://irclogs.ubuntu.com/2010/03/30/%23ubuntu-arm.txt
>>
>>> Andrew Stubbs, Michael Hope in Linaro's toolchain team are working
>>> hard on this gcc issue. there have been many update today:
>>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48783
>>
>> Is this just some Linaro toolchain that has the issue rather than a
>> vanilla GCC release?  If so and they fix the compiler bug it doesn't
>> seem terribly useful to bodge it in mainline.
>>
>
> i am guessing it is a generic gcc issue since Michael posted it at
> http://gcc.gnu.org/bugzilla not Linaro's Launchpad. not sure :-)

Linaro doesn't exist yet when the discussion happened at
http://irclogs.ubuntu.com/2010/03/30/%23ubuntu-arm.txt discussion:

" [19:03] <nosse1> I got this while compiling: "ERROR:
"__aeabi_uldivmod" [sound/soc/codecs/snd-soc-wm8974.ko] undefined!"
[19:04] <nosse1> Now, I can disable the driver alltogether, but is
this related to the CSL cross compiler?
[19:04] <hrw> nosse1: google should give answer - common problem it was
[19:04] <nosse1> hehe - sorry, you're right
"

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

[Michael Hope]

Hi Mark.  The fault exists in FSF GCC 4.5.2 and Linaro GCC
4.5-2011.04.  The fault does not exist in FSF GCC 4.6.0 or Linaro GCC
4.6-2011.04.

-- Michael

On Thu, Apr 28, 2011 at 3:12 AM, Mark Brown
<broonie-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org> wrote:
> On Wed, Apr 27, 2011 at 11:00:18PM +0800, Barry Song wrote:
>> 2011/4/27 Mark Brown <broonie-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org>
>
>> > If we do have to do something in the callers rather than in do_div() the
>> > annotation seems substantially more taseful than inserting a random asm
>> > into the code.
>
>> I agree. for this patch which will not be applied, people can just get
>> information about how to workaround the gcc issue while they have the
>> same problem. google can find there are other people who failed to
>> compile wm8974 module too. eg.
>> http://irclogs.ubuntu.com/2010/03/30/%23ubuntu-arm.txt
>
>> Andrew Stubbs, Michael Hope in Linaro's toolchain team are working
>> hard on this gcc issue. there have been many update today:
>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48783
>
> Is this just some Linaro toolchain that has the issue rather than a
> vanilla GCC release?  If so and they fix the compiler bug it doesn't
> seem terribly useful to bodge it in mainline.
>
> _______________________________________________
> linaro-toolchain mailing list
> linaro-toolchain-cunTk1MwBs8s++Sfvej+rw@public.gmane.org
> http://lists.linaro.org/mailman/listinfo/linaro-toolchain
>

Re: [PATCH] ASoC: prevent compilers from optimising pll calculation into __aeabi__uldivmod

[Mark Brown]

On Thu, Apr 28, 2011 at 10:30:24AM +1200, Michael Hope wrote:

Don't top post!

> Hi Mark.  The fault exists in FSF GCC 4.5.2 and Linaro GCC
> 4.5-2011.04.  The fault does not exist in FSF GCC 4.6.0 or Linaro GCC
> 4.6-2011.04.

Given that nobody's reported it previously and there's already a new GCC
release I'm not sure it's worth worry about - it's a fairly clear
compiler bug.

Re: [PATCH] ASoC: prevent compilers from optimising pll calculation into __aeabi__uldivmod

[Mark Brown]

On Wed, Apr 27, 2011 at 04:24:44PM +0800, Barry Song wrote:
> 2011/4/27 Takashi Iwai <tiwai@suse.de>:

> > 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.

It's a macro which expands to a problem so we should make it expand to
something which includes the fix as well rather than going round and
fixing each and every caller.

Re: [PATCH] ASoC: prevent compilers from optimising pll calculation into __aeabi__uldivmod

[Stephen Warren]

Barry Song wrote at Wednesday, April 27, 2011 1:28 AM:
> 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.

Aren't there compiler flags that tell gcc it isn't operating in a hosted(?)
environment, and hence not to emit calls to these functions? If so, I
imagine they should be added to the kernel's core (or ARM arch ) makefiles.

I doubt __aeabi_uldivmod is the only function of this type. How was this
solved for other such functions; does the kernel implement the AEABI
functions, and this implementation is simply missing?

But yes either way, ask on the main kernel or ARM kernel mailing list
(ARM now CC'd)

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;

-- 
nvpublic

Re: [PATCH] ASoC: prevent compilers from optimising pll calculation into __aeabi__uldivmod

[Mark Brown]

On Wed, Apr 27, 2011 at 07:59:39AM -0700, Stephen Warren wrote:

> Aren't there compiler flags that tell gcc it isn't operating in a hosted(?)
> environment, and hence not to emit calls to these functions? If so, I
> imagine they should be added to the kernel's core (or ARM arch ) makefiles.

IIRC there's some intrinsics (usually for operations like divisions)
which GCC expects to be provided even in a free standing environment.

Re: [PATCH] ASoC: prevent compilers from optimising pll calculation into __aeabi__uldivmod

[Barry Song]

2011/4/27 Stephen Warren <swarren@nvidia.com>:
> Barry Song wrote at Wednesday, April 27, 2011 1:28 AM:
>> 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.
>
> Aren't there compiler flags that tell gcc it isn't operating in a hosted(?)
> environment, and hence not to emit calls to these functions? If so, I
> imagine they should be added to the kernel's core (or ARM arch ) makefiles.

not real. it is right for gcc to call __aeabi_uldivmod while it think
it is good. most time, people change kernel codes to avoid this kind
of optimization:

http://comments.gmane.org/gmane.linux.kernel/965262

Another example is time.h:

{
ns += a->tv_nsec;
while(unlikely(ns >= NSEC_PER_SEC)) {
+ /* The following asm() prevents the compiler from
+ * optimising this loop into a modulo operation. */
+ asm("" : "+r"(ns));
+
ns -= NSEC_PER_SEC;
a->tv_sec++;
}

>
> I doubt __aeabi_uldivmod is the only function of this type. How was this
> solved for other such functions; does the kernel implement the AEABI
> functions, and this implementation is simply missing?
>
> But yes either way, ask on the main kernel or ARM kernel mailing list
> (ARM now CC'd)
>
> 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;
>
> --
> nvpublic
>
>
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Alsa-devel@alsa-project.org
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Re: [PATCH] ASoC: prevent compilers from optimising pll calculation into __aeabi__uldivmod

[Barry Song]

2011/4/27 Stephen Warren <swarren@nvidia.com>:
> Barry Song wrote at Wednesday, April 27, 2011 1:28 AM:
>> 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.
>
> Aren't there compiler flags that tell gcc it isn't operating in a hosted(?)
> environment, and hence not to emit calls to these functions? If so, I
> imagine they should be added to the kernel's core (or ARM arch ) makefiles.
>
> I doubt __aeabi_uldivmod is the only function of this type. How was this
> solved for other such functions; does the kernel implement the AEABI
> functions, and this implementation is simply missing?

__aeabi_uldivmod is not implemented by kernel, others are implemented
in arch/arm/lib/lib1funcs.S:
extern void __aeabi_idiv(void);
extern void __aeabi_idivmod(void);
extern void __aeabi_lasr(void);
extern void __aeabi_llsl(void);
extern void __aeabi_llsr(void);
extern void __aeabi_lmul(void);
extern void __aeabi_uidiv(void);
extern void __aeabi_uidivmod(void);
extern void __aeabi_ulcmp(void);

>
> But yes either way, ask on the main kernel or ARM kernel mailing list
> (ARM now CC'd)
>
> 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;
>
> --
> nvpublic
>
>
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