Patchwork [U-Boot] arm1136: cosmetic: Remove double test on CONFIG_SYS_DCACHE_OFF

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Submitter Benoît Thébaudeau
Date Aug. 14, 2012, 1:17 p.m.
Message ID <616950058.2399354.1344950229125.JavaMail.root@advansee.com>
Download mbox | patch
Permalink /patch/177263/
State Superseded
Delegated to: Albert ARIBAUD
Headers show

Comments

Benoît Thébaudeau - Aug. 14, 2012, 1:17 p.m.
Remove a redundant '#ifndef CONFIG_SYS_DCACHE_OFF' nested in the same #ifndef.

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
---
 .../arch/arm/cpu/arm1136/cpu.c                     |    2 --
 1 file changed, 2 deletions(-)
Albert ARIBAUD - Oct. 4, 2012, 1:39 p.m.
Hi Benoît,

On Tue, 14 Aug 2012 15:17:09 +0200 (CEST), Benoît Thébaudeau
<benoit.thebaudeau@advansee.com> wrote:

> Remove a redundant '#ifndef CONFIG_SYS_DCACHE_OFF' nested in the same #ifndef.
> 
> Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
> Cc: Albert Aribaud <albert.u.boot@aribaud.net>
> ---
>  .../arch/arm/cpu/arm1136/cpu.c                     |    2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git u-boot-4d3c95f.orig/arch/arm/cpu/arm1136/cpu.c u-boot-4d3c95f/arch/arm/cpu/arm1136/cpu.c
> index b98e3d9..1136c1d 100644
> --- u-boot-4d3c95f.orig/arch/arm/cpu/arm1136/cpu.c
> +++ u-boot-4d3c95f/arch/arm/cpu/arm1136/cpu.c
> @@ -146,9 +146,7 @@ void enable_caches(void)
>  #ifndef CONFIG_SYS_ICACHE_OFF
>  	icache_enable();
>  #endif
> -#ifndef CONFIG_SYS_DCACHE_OFF
>  	dcache_enable();
> -#endif
>  }
>  
>  #else /* #ifndef CONFIG_SYS_DCACHE_OFF */

I'll NAK this one because:

1) obviously the big #ifndef CONFIG_SYS_DCACHE_OFF / #else /#endif is
there to provide either working D$ functions or empty ones;

2) enable_caches() exists only in the "then" branch, not at all in the
"else" branch, which makes it a surprising exception;

3) enable_caches() is the only function in the if/then/else acting on I$
as well as D$;

... so I suspect it did not actually belong in the big if/then/else in
the first place and should not be modified but moved after the #endif.

Please provide a V2 patch, I promise it'll get processed faster than
this V1.

Amicalement,
Benoît Thébaudeau - Oct. 4, 2012, 4:57 p.m.
Hi Albert,

On Thursday, October 4, 2012 3:39:41 PM, Albert ARIBAUD wrote:
> Hi Benoît,
> 
> On Tue, 14 Aug 2012 15:17:09 +0200 (CEST), Benoît Thébaudeau
> <benoit.thebaudeau@advansee.com> wrote:
> 
> > Remove a redundant '#ifndef CONFIG_SYS_DCACHE_OFF' nested in the
> > same #ifndef.
> > 
> > Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
> > Cc: Albert Aribaud <albert.u.boot@aribaud.net>
> > ---
> >  .../arch/arm/cpu/arm1136/cpu.c                     |    2 --
> >  1 file changed, 2 deletions(-)
> > 
> > diff --git u-boot-4d3c95f.orig/arch/arm/cpu/arm1136/cpu.c
> > u-boot-4d3c95f/arch/arm/cpu/arm1136/cpu.c
> > index b98e3d9..1136c1d 100644
> > --- u-boot-4d3c95f.orig/arch/arm/cpu/arm1136/cpu.c
> > +++ u-boot-4d3c95f/arch/arm/cpu/arm1136/cpu.c
> > @@ -146,9 +146,7 @@ void enable_caches(void)
> >  #ifndef CONFIG_SYS_ICACHE_OFF
> >  	icache_enable();
> >  #endif
> > -#ifndef CONFIG_SYS_DCACHE_OFF
> >  	dcache_enable();
> > -#endif
> >  }
> >  
> >  #else /* #ifndef CONFIG_SYS_DCACHE_OFF */
> 
> I'll NAK this one because:
> 
> 1) obviously the big #ifndef CONFIG_SYS_DCACHE_OFF / #else /#endif is
> there to provide either working D$ functions or empty ones;
> 
> 2) enable_caches() exists only in the "then" branch, not at all in
> the
> "else" branch, which makes it a surprising exception;
> 
> 3) enable_caches() is the only function in the if/then/else acting on
> I$
> as well as D$;
> 
> ... so I suspect it did not actually belong in the big if/then/else
> in
> the first place and should not be modified but moved after the
> #endif.

I agree, simply because with the current code, enable_caches() does not enable
icache if CONFIG_SYS_ICACHE_OFF is not defined but CONFIG_SYS_DCACHE_OFF is.

But is it enough to move it? We could indeed move it after the #endif, but also
change it to:

---
#if !defined(CONFIG_SYS_ICACHE_OFF) || !defined(CONFIG_SYS_DCACHE_OFF)
void enable_caches(void)
{
#ifndef CONFIG_SYS_ICACHE_OFF
	icache_enable();
#endif
#ifndef CONFIG_SYS_DCACHE_OFF
	dcache_enable();
#endif
}
#endif
---

In that way, the default __enable_caches() from cache.c (outputting
"WARNING: Caches not enabled\n") would be linked if both CONFIG_SYS_ICACHE_OFF
and CONFIG_SYS_DCACHE_OFF are defined.

Do you agree?

> Please provide a V2 patch, I promise it'll get processed faster than
> this V1.

OK ;) , I'll do that after your answer to the question above.

Best regards,
Benoît
Albert ARIBAUD - Oct. 5, 2012, 5:05 p.m.
Hi Benoît,

On Thu, 4 Oct 2012 18:57:19 +0200 (CEST), Benoît Thébaudeau
<benoit.thebaudeau@advansee.com> wrote:

> Hi Albert,
> 
> On Thursday, October 4, 2012 3:39:41 PM, Albert ARIBAUD wrote:
> > Hi Benoît,
> > 
> > On Tue, 14 Aug 2012 15:17:09 +0200 (CEST), Benoît Thébaudeau
> > <benoit.thebaudeau@advansee.com> wrote:
> > 
> > > Remove a redundant '#ifndef CONFIG_SYS_DCACHE_OFF' nested in the
> > > same #ifndef.
> > > 
> > > Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
> > > Cc: Albert Aribaud <albert.u.boot@aribaud.net>
> > > ---
> > >  .../arch/arm/cpu/arm1136/cpu.c                     |    2 --
> > >  1 file changed, 2 deletions(-)
> > > 
> > > diff --git u-boot-4d3c95f.orig/arch/arm/cpu/arm1136/cpu.c
> > > u-boot-4d3c95f/arch/arm/cpu/arm1136/cpu.c
> > > index b98e3d9..1136c1d 100644
> > > --- u-boot-4d3c95f.orig/arch/arm/cpu/arm1136/cpu.c
> > > +++ u-boot-4d3c95f/arch/arm/cpu/arm1136/cpu.c
> > > @@ -146,9 +146,7 @@ void enable_caches(void)
> > >  #ifndef CONFIG_SYS_ICACHE_OFF
> > >  	icache_enable();
> > >  #endif
> > > -#ifndef CONFIG_SYS_DCACHE_OFF
> > >  	dcache_enable();
> > > -#endif
> > >  }
> > >  
> > >  #else /* #ifndef CONFIG_SYS_DCACHE_OFF */
> > 
> > I'll NAK this one because:
> > 
> > 1) obviously the big #ifndef CONFIG_SYS_DCACHE_OFF / #else /#endif is
> > there to provide either working D$ functions or empty ones;
> > 
> > 2) enable_caches() exists only in the "then" branch, not at all in
> > the
> > "else" branch, which makes it a surprising exception;
> > 
> > 3) enable_caches() is the only function in the if/then/else acting on
> > I$
> > as well as D$;
> > 
> > ... so I suspect it did not actually belong in the big if/then/else
> > in
> > the first place and should not be modified but moved after the
> > #endif.
> 
> I agree, simply because with the current code, enable_caches() does not enable
> icache if CONFIG_SYS_ICACHE_OFF is not defined but CONFIG_SYS_DCACHE_OFF is.
> 
> But is it enough to move it? We could indeed move it after the #endif, but also
> change it to:
> 
> ---
> #if !defined(CONFIG_SYS_ICACHE_OFF) || !defined(CONFIG_SYS_DCACHE_OFF)
> void enable_caches(void)
> {
> #ifndef CONFIG_SYS_ICACHE_OFF
> 	icache_enable();
> #endif
> #ifndef CONFIG_SYS_DCACHE_OFF
> 	dcache_enable();
> #endif
> }
> #endif
> ---
> 
> In that way, the default __enable_caches() from cache.c (outputting
> "WARNING: Caches not enabled\n") would be linked if both CONFIG_SYS_ICACHE_OFF
> and CONFIG_SYS_DCACHE_OFF are defined.
> 
> Do you agree?

When CONFIG_SYS_DCACHE_OFF, dcache functions are not compiled out, they
are compiled in but empty. IOW, even with caches off, the API remains
callable albeit useless. This is done so that client code does not
have to test CONFIG_SYS_DCACHE_OFF before deciding to call the API or
not.

Therefore, for consistency, enable_caches() should be defined and empty
even when both CONFIG_SYS_DCACHE_OFF and CONFIG_SYS_ICACHE_OFF are
defined, which is not the case in the example above due to the
enclosing #if/#endif.

> > Please provide a V2 patch, I promise it'll get processed faster than
> > this V1.
> 
> OK ;) , I'll do that after your answer to the question above.
> 
> Best regards,
> Benoît

Amicalement,
Benoît Thébaudeau - Oct. 5, 2012, 5:36 p.m.
Hi Albert,

On Friday, October 5, 2012 7:05:19 PM, Albert ARIBAUD wrote:
> Hi Benoît,
> 
> On Thu, 4 Oct 2012 18:57:19 +0200 (CEST), Benoît Thébaudeau
> <benoit.thebaudeau@advansee.com> wrote:
> 
> > Hi Albert,
> > 
> > On Thursday, October 4, 2012 3:39:41 PM, Albert ARIBAUD wrote:
> > > Hi Benoît,
> > > 
> > > On Tue, 14 Aug 2012 15:17:09 +0200 (CEST), Benoît Thébaudeau
> > > <benoit.thebaudeau@advansee.com> wrote:
> > > 
> > > > Remove a redundant '#ifndef CONFIG_SYS_DCACHE_OFF' nested in
> > > > the
> > > > same #ifndef.
> > > > 
> > > > Signed-off-by: Benoît Thébaudeau
> > > > <benoit.thebaudeau@advansee.com>
> > > > Cc: Albert Aribaud <albert.u.boot@aribaud.net>
> > > > ---
> > > >  .../arch/arm/cpu/arm1136/cpu.c                     |    2 --
> > > >  1 file changed, 2 deletions(-)
> > > > 
> > > > diff --git u-boot-4d3c95f.orig/arch/arm/cpu/arm1136/cpu.c
> > > > u-boot-4d3c95f/arch/arm/cpu/arm1136/cpu.c
> > > > index b98e3d9..1136c1d 100644
> > > > --- u-boot-4d3c95f.orig/arch/arm/cpu/arm1136/cpu.c
> > > > +++ u-boot-4d3c95f/arch/arm/cpu/arm1136/cpu.c
> > > > @@ -146,9 +146,7 @@ void enable_caches(void)
> > > >  #ifndef CONFIG_SYS_ICACHE_OFF
> > > >  	icache_enable();
> > > >  #endif
> > > > -#ifndef CONFIG_SYS_DCACHE_OFF
> > > >  	dcache_enable();
> > > > -#endif
> > > >  }
> > > >  
> > > >  #else /* #ifndef CONFIG_SYS_DCACHE_OFF */
> > > 
> > > I'll NAK this one because:
> > > 
> > > 1) obviously the big #ifndef CONFIG_SYS_DCACHE_OFF / #else
> > > /#endif is
> > > there to provide either working D$ functions or empty ones;
> > > 
> > > 2) enable_caches() exists only in the "then" branch, not at all
> > > in
> > > the
> > > "else" branch, which makes it a surprising exception;
> > > 
> > > 3) enable_caches() is the only function in the if/then/else
> > > acting on
> > > I$
> > > as well as D$;
> > > 
> > > ... so I suspect it did not actually belong in the big
> > > if/then/else
> > > in
> > > the first place and should not be modified but moved after the
> > > #endif.
> > 
> > I agree, simply because with the current code, enable_caches() does
> > not enable
> > icache if CONFIG_SYS_ICACHE_OFF is not defined but
> > CONFIG_SYS_DCACHE_OFF is.
> > 
> > But is it enough to move it? We could indeed move it after the
> > #endif, but also
> > change it to:
> > 
> > ---
> > #if !defined(CONFIG_SYS_ICACHE_OFF) ||
> > !defined(CONFIG_SYS_DCACHE_OFF)
> > void enable_caches(void)
> > {
> > #ifndef CONFIG_SYS_ICACHE_OFF
> > 	icache_enable();
> > #endif
> > #ifndef CONFIG_SYS_DCACHE_OFF
> > 	dcache_enable();
> > #endif
> > }
> > #endif
> > ---
> > 
> > In that way, the default __enable_caches() from cache.c (outputting
> > "WARNING: Caches not enabled\n") would be linked if both
> > CONFIG_SYS_ICACHE_OFF
> > and CONFIG_SYS_DCACHE_OFF are defined.
> > 
> > Do you agree?
> 
> When CONFIG_SYS_DCACHE_OFF, dcache functions are not compiled out,
> they
> are compiled in but empty. IOW, even with caches off, the API remains
> callable albeit useless. This is done so that client code does not
> have to test CONFIG_SYS_DCACHE_OFF before deciding to call the API or
> not.
> 
> Therefore, for consistency, enable_caches() should be defined and
> empty
> even when both CONFIG_SYS_DCACHE_OFF and CONFIG_SYS_ICACHE_OFF are
> defined, which is not the case in the example above due to the
> enclosing #if/#endif.

In the example, enable_caches() is still defined if both CONFIG_SYS_DCACHE_OFF
and CONFIG_SYS_ICACHE_OFF are defined. See arch/arm/lib/cache.c:
---
/*
 * Default implementation of enable_caches()
 * Real implementation should be in platform code
 */
void __enable_caches(void)
{
	puts("WARNING: Caches not enabled\n");
}
void enable_caches(void)
	__attribute__((weak, alias("__enable_caches")));
---

But you're right, it's not empty in this case. Is it that you want to remove
this message in this case?

This default implementation is used in the same way for several other ARM
targets.

Best regards,
Benoît
Albert ARIBAUD - Oct. 5, 2012, 6:15 p.m.
Hi Benoît,

On Fri, 5 Oct 2012 19:36:34 +0200 (CEST), Benoît Thébaudeau
<benoit.thebaudeau@advansee.com> wrote:

> Hi Albert,
> 
> On Friday, October 5, 2012 7:05:19 PM, Albert ARIBAUD wrote:
> > Hi Benoît,
> > 
> > On Thu, 4 Oct 2012 18:57:19 +0200 (CEST), Benoît Thébaudeau
> > <benoit.thebaudeau@advansee.com> wrote:
> > 
> > > Hi Albert,
> > > 
> > > On Thursday, October 4, 2012 3:39:41 PM, Albert ARIBAUD wrote:
> > > > Hi Benoît,
> > > > 
> > > > On Tue, 14 Aug 2012 15:17:09 +0200 (CEST), Benoît Thébaudeau
> > > > <benoit.thebaudeau@advansee.com> wrote:
> > > > 
> > > > > Remove a redundant '#ifndef CONFIG_SYS_DCACHE_OFF' nested in
> > > > > the
> > > > > same #ifndef.
> > > > > 
> > > > > Signed-off-by: Benoît Thébaudeau
> > > > > <benoit.thebaudeau@advansee.com>
> > > > > Cc: Albert Aribaud <albert.u.boot@aribaud.net>
> > > > > ---
> > > > >  .../arch/arm/cpu/arm1136/cpu.c                     |    2 --
> > > > >  1 file changed, 2 deletions(-)
> > > > > 
> > > > > diff --git u-boot-4d3c95f.orig/arch/arm/cpu/arm1136/cpu.c
> > > > > u-boot-4d3c95f/arch/arm/cpu/arm1136/cpu.c
> > > > > index b98e3d9..1136c1d 100644
> > > > > --- u-boot-4d3c95f.orig/arch/arm/cpu/arm1136/cpu.c
> > > > > +++ u-boot-4d3c95f/arch/arm/cpu/arm1136/cpu.c
> > > > > @@ -146,9 +146,7 @@ void enable_caches(void)
> > > > >  #ifndef CONFIG_SYS_ICACHE_OFF
> > > > >  	icache_enable();
> > > > >  #endif
> > > > > -#ifndef CONFIG_SYS_DCACHE_OFF
> > > > >  	dcache_enable();
> > > > > -#endif
> > > > >  }
> > > > >  
> > > > >  #else /* #ifndef CONFIG_SYS_DCACHE_OFF */
> > > > 
> > > > I'll NAK this one because:
> > > > 
> > > > 1) obviously the big #ifndef CONFIG_SYS_DCACHE_OFF / #else
> > > > /#endif is
> > > > there to provide either working D$ functions or empty ones;
> > > > 
> > > > 2) enable_caches() exists only in the "then" branch, not at all
> > > > in
> > > > the
> > > > "else" branch, which makes it a surprising exception;
> > > > 
> > > > 3) enable_caches() is the only function in the if/then/else
> > > > acting on
> > > > I$
> > > > as well as D$;
> > > > 
> > > > ... so I suspect it did not actually belong in the big
> > > > if/then/else
> > > > in
> > > > the first place and should not be modified but moved after the
> > > > #endif.
> > > 
> > > I agree, simply because with the current code, enable_caches() does
> > > not enable
> > > icache if CONFIG_SYS_ICACHE_OFF is not defined but
> > > CONFIG_SYS_DCACHE_OFF is.
> > > 
> > > But is it enough to move it? We could indeed move it after the
> > > #endif, but also
> > > change it to:
> > > 
> > > ---
> > > #if !defined(CONFIG_SYS_ICACHE_OFF) ||
> > > !defined(CONFIG_SYS_DCACHE_OFF)
> > > void enable_caches(void)
> > > {
> > > #ifndef CONFIG_SYS_ICACHE_OFF
> > > 	icache_enable();
> > > #endif
> > > #ifndef CONFIG_SYS_DCACHE_OFF
> > > 	dcache_enable();
> > > #endif
> > > }
> > > #endif
> > > ---
> > > 
> > > In that way, the default __enable_caches() from cache.c (outputting
> > > "WARNING: Caches not enabled\n") would be linked if both
> > > CONFIG_SYS_ICACHE_OFF
> > > and CONFIG_SYS_DCACHE_OFF are defined.
> > > 
> > > Do you agree?
> > 
> > When CONFIG_SYS_DCACHE_OFF, dcache functions are not compiled out,
> > they
> > are compiled in but empty. IOW, even with caches off, the API remains
> > callable albeit useless. This is done so that client code does not
> > have to test CONFIG_SYS_DCACHE_OFF before deciding to call the API or
> > not.
> > 
> > Therefore, for consistency, enable_caches() should be defined and
> > empty
> > even when both CONFIG_SYS_DCACHE_OFF and CONFIG_SYS_ICACHE_OFF are
> > defined, which is not the case in the example above due to the
> > enclosing #if/#endif.
> 
> In the example, enable_caches() is still defined if both CONFIG_SYS_DCACHE_OFF
> and CONFIG_SYS_ICACHE_OFF are defined. See arch/arm/lib/cache.c:
> ---
> /*
>  * Default implementation of enable_caches()
>  * Real implementation should be in platform code
>  */
> void __enable_caches(void)
> {
> 	puts("WARNING: Caches not enabled\n");
> }
> void enable_caches(void)
> 	__attribute__((weak, alias("__enable_caches")));
> ---
> 
> But you're right, it's not empty in this case. Is it that you want to remove
> this message in this case?
> 
> This default implementation is used in the same way for several other ARM
> targets.

OK, I see your point: enable_cache() needs not be defined here if
caches are #define'd out, because there is a weak default definition
in arch/arm/lib/cache.c that just prints a warning about caches not
being enabled.

But then, the same holds for flush_dcache_all and flush_cache, which
are not compiled out from as enable_cache is -- and if they were, then
the arch/arm/lib/cache.c versions would kick in, and those are not
empty, especially __flush_cache which contains a conditional call to...
arm1136_cache_flush()

That is certainly not consistent... And on second thought, not defining
a cache-related function at cpu level if caches are compiled out is
more sensible than defining it empty.

All this could undergo a greater change to move cpu-specifics out of
the ARM library so that all lib functions are empty or generic, and
define cpu-specific functions only if caches are compiled in... But
I won't ask for something that's far beyond the goal of your patch.

Conclusion: V2 is good as it is. I'll apply it on /next.

> Best regards,
> Benoît

Amicalement,

Patch

diff --git u-boot-4d3c95f.orig/arch/arm/cpu/arm1136/cpu.c u-boot-4d3c95f/arch/arm/cpu/arm1136/cpu.c
index b98e3d9..1136c1d 100644
--- u-boot-4d3c95f.orig/arch/arm/cpu/arm1136/cpu.c
+++ u-boot-4d3c95f/arch/arm/cpu/arm1136/cpu.c
@@ -146,9 +146,7 @@  void enable_caches(void)
 #ifndef CONFIG_SYS_ICACHE_OFF
 	icache_enable();
 #endif
-#ifndef CONFIG_SYS_DCACHE_OFF
 	dcache_enable();
-#endif
 }
 
 #else /* #ifndef CONFIG_SYS_DCACHE_OFF */