@@ -117,6 +117,7 @@ config MTD_MAP_BANK_WIDTH_16
config MTD_MAP_BANK_WIDTH_32
bool "Support 256-bit buswidth" if MTD_CFI_GEOMETRY
+ select MTD_COMPLEX_MAPPINGS if HAS_IOMEM
default n
help
If you wish to support CFI devices on a physical bus which is
@@ -122,18 +122,13 @@
#endif
#ifdef CONFIG_MTD_MAP_BANK_WIDTH_32
-# ifdef map_bankwidth
-# undef map_bankwidth
-# define map_bankwidth(map) ((map)->bankwidth)
-# undef map_bankwidth_is_large
-# define map_bankwidth_is_large(map) (map_bankwidth(map) > BITS_PER_LONG/8)
-# undef map_words
-# define map_words(map) map_calc_words(map)
-# else
-# define map_bankwidth(map) 32
-# define map_bankwidth_is_large(map) (1)
-# define map_words(map) map_calc_words(map)
-# endif
+/* always use indirect access for 256-bit to preserve kernel stack */
+# undef map_bankwidth
+# define map_bankwidth(map) ((map)->bankwidth)
+# undef map_bankwidth_is_large
+# define map_bankwidth_is_large(map) (map_bankwidth(map) > BITS_PER_LONG/8)
+# undef map_words
+# define map_words(map) map_calc_words(map)
#define map_bankwidth_is_32(map) (map_bankwidth(map) == 32)
#undef MAX_MAP_BANKWIDTH
#define MAX_MAP_BANKWIDTH 32
When map_word gets too large, we use a lot of kernel stack, and for MTD_MAP_BANK_WIDTH_32, this means we use more than the recommended 1024 bytes in a number of functions: 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 1336 bytes is larger than 1024 bytes [-Wframe-larger-than=] drivers/mtd/chips/cfi_cmdset_0020.c: In function 'cfi_staa_erase_varsize': drivers/mtd/chips/cfi_cmdset_0020.c:972:1: warning: the frame size of 1208 bytes is larger than 1024 bytes [-Wframe-larger-than=] drivers/mtd/chips/cfi_cmdset_0001.c: In function 'do_write_buffer': drivers/mtd/chips/cfi_cmdset_0001.c:1835:1: warning: the frame size of 1240 bytes is larger than 1024 bytes [-Wframe-larger-than=] This can be avoided if all operations on the map word are done indirectly and the stack gets reused between the calls. We can mostly achieve this by selecting MTD_COMPLEX_MAPPINGS whenever MTD_MAP_BANK_WIDTH_32 is set, but for the case that no other bank width is enabled, we also need to use a non-constant map_bankwidth() to convince the compiler to use less stack. Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- v2: added 'if HAS_IOMEM' to avoid a Kconfig warning on user-mode-linux. Originally sent out on Jan 1, sorry for taking my time to follow up with a new version. drivers/mtd/chips/Kconfig | 1 + include/linux/mtd/map.h | 19 +++++++------------ 2 files changed, 8 insertions(+), 12 deletions(-) -- 2.7.0