[PATCH] MTD: cfi: reduce stack size

[PATCH] MTD: cfi: reduce stack size

[Arnd Bergmann]

The cfi_staa_write_buffers function uses a large amount of ernel stack
whenever CONFIG_MTD_MAP_BANK_WIDTH_32 is set, and that results in a
warning on ARM allmodconfig builds:

drivers/mtd/chips/cfi_cmdset_0020.c: In function 'cfi_staa_write_buffers':
drivers/mtd/chips/cfi_cmdset_0020.c:651:1: warning: the frame size of 1208 bytes is larger than 1024 bytes [-Wframe-larger-than=]

It turns out that this is largely a result of a suboptimal implementation
of map_word_andequal(). Replacing this function with a straightforward
one reduces the stack size in this function by exactly 200 bytes,
shrinks the .text segment for this file from 27648 bytes to 26608 bytes,
and makes the warning go away.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

diff --git a/include/linux/mtd/map.h b/include/linux/mtd/map.h
index 5f487d776411..2d2457bee50c 100644
--- a/include/linux/mtd/map.h
+++ b/include/linux/mtd/map.h
@@ -314,7 +314,15 @@ static inline map_word map_word_or(struct map_info *map, map_word val1, map_word
 	return r;
 }
 
-#define map_word_andequal(m, a, b, z) map_word_equal(m, z, map_word_and(m, a, b))
+static inline int map_word_andequal(struct map_info *map, map_word val1, map_word val2, map_word val3)
+{
+	int i;
+	for (i=0; i<map_words(map); i++) {
+		if ((val1.x[i] & val2.x[i]) != val3.x[i])
+			return 0;
+	}
+	return 1;
+}
 
 static inline int map_word_bitsset(struct map_info *map, map_word val1, map_word val2)
 {

Re: [PATCH] MTD: cfi: reduce stack size

[Ezequiel Garcia]

On 03/09/2015 10:58 AM, Arnd Bergmann wrote:
> The cfi_staa_write_buffers function uses a large amount of ernel stack

Typo: "ernel"

> whenever CONFIG_MTD_MAP_BANK_WIDTH_32 is set, and that results in a
> warning on ARM allmodconfig builds:
> 
> drivers/mtd/chips/cfi_cmdset_0020.c: In function 'cfi_staa_write_buffers':
> drivers/mtd/chips/cfi_cmdset_0020.c:651:1: warning: the frame size of 1208 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> 
> It turns out that this is largely a result of a suboptimal implementation
> of map_word_andequal(). Replacing this function with a straightforward
> one reduces the stack size in this function by exactly 200 bytes,
> shrinks the .text segment for this file from 27648 bytes to 26608 bytes,
> and makes the warning go away.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> 
> diff --git a/include/linux/mtd/map.h b/include/linux/mtd/map.h
> index 5f487d776411..2d2457bee50c 100644
> --- a/include/linux/mtd/map.h
> +++ b/include/linux/mtd/map.h
> @@ -314,7 +314,15 @@ static inline map_word map_word_or(struct map_info *map, map_word val1, map_word
>  	return r;
>  }
>  
> -#define map_word_andequal(m, a, b, z) map_word_equal(m, z, map_word_and(m, a, b))
> +static inline int map_word_andequal(struct map_info *map, map_word val1, map_word val2, map_word val3)
> +{
> +	int i;
> +	for (i=0; i<map_words(map); i++) {

Nit:

for (i = 0; i < map_words(map); i++)

-- 
Ezequiel Garcia, VanguardiaSur
www.vanguardiasur.com.ar

Re: [PATCH] MTD: cfi: reduce stack size

[Arnd Bergmann]

On Monday 09 March 2015 12:58:54 Ezequiel Garcia wrote:
> On 03/09/2015 10:58 AM, Arnd Bergmann wrote:
> > The cfi_staa_write_buffers function uses a large amount of ernel stack
> 
> Typo: "ernel"

ok

> > whenever CONFIG_MTD_MAP_BANK_WIDTH_32 is set, and that results in a
> > warning on ARM allmodconfig builds:
> > 
> > drivers/mtd/chips/cfi_cmdset_0020.c: In function 'cfi_staa_write_buffers':
> > drivers/mtd/chips/cfi_cmdset_0020.c:651:1: warning: the frame size of 1208 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> > 
> > It turns out that this is largely a result of a suboptimal implementation
> > of map_word_andequal(). Replacing this function with a straightforward
> > one reduces the stack size in this function by exactly 200 bytes,
> > shrinks the .text segment for this file from 27648 bytes to 26608 bytes,
> > and makes the warning go away.
> > 
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > 
> > diff --git a/include/linux/mtd/map.h b/include/linux/mtd/map.h
> > index 5f487d776411..2d2457bee50c 100644
> > --- a/include/linux/mtd/map.h
> > +++ b/include/linux/mtd/map.h
> > @@ -314,7 +314,15 @@ static inline map_word map_word_or(struct map_info *map, map_word val1, map_word
> >  	return r;
> >  }
> >  
> > -#define map_word_andequal(m, a, b, z) map_word_equal(m, z, map_word_and(m, a, b))
> > +static inline int map_word_andequal(struct map_info *map, map_word val1, map_word val2, map_word val3)
> > +{
> > +	int i;
> > +	for (i=0; i<map_words(map); i++) {
> 
> Nit:
> 
> for (i = 0; i < map_words(map); i++)

It's the same as five other copies of the same loop in this file, but I've
changed this one now.

Thanks,

	Arnd