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SubjectRe: [PATCH v3] mtd: cfi: reduce stack size
On Tue, Mar 10, 2015 at 05:48:37PM +0100, Arnd Bergmann wrote:
> The cfi_staa_write_buffers function uses a large amount of kernel 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.

Patch looks OK to me, and those results are nice.

Did you (or anyone else) do any testing?

> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> v3: more whitespace changes
> v2: whitespace changes
>
> diff --git a/include/linux/mtd/map.h b/include/linux/mtd/map.h
> index 47c59991491b..29975c73a953 100644
> --- a/include/linux/mtd/map.h
> +++ b/include/linux/mtd/map.h
> @@ -316,7 +316,17 @@ 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)
> {
>


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