summaryrefslogtreecommitdiff
path: root/Documentation/DocBook/media
diff options
context:
space:
mode:
authorHerton Ronaldo Krzesinski <herton.krzesinski@canonical.com>2012-05-16 23:21:52 +0400
committerDavid Woodhouse <David.Woodhouse@intel.com>2012-07-06 19:59:33 +0400
commit596fd46268634082314b3af1ded4612e1b7f3f03 (patch)
treeeaec1116cfc24d25b54912dcd71f34f761f74491 /Documentation/DocBook/media
parent021796b892dcad45743f3196e3eef7222870dd55 (diff)
downloadlinux-596fd46268634082314b3af1ded4612e1b7f3f03.tar.xz
mtd: nandsim: don't open code a do_div helper
We don't need to open code the divide function, just use div_u64 that already exists and do the same job. While this is a straightforward clean up, there is more to that, the real motivation for this. While building on a cross compiling environment in armel, using gcc 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5), I was getting the following build error: ERROR: "__aeabi_uldivmod" [drivers/mtd/nand/nandsim.ko] undefined! After investigating with objdump and hand built assembly version generated with the compiler, I narrowed __aeabi_uldivmod as being generated from the divide function. When nandsim.c is built with -fno-inline-functions-called-once, that happens when CONFIG_DEBUG_SECTION_MISMATCH is enabled, the do_div optimization in arch/arm/include/asm/div64.h doesn't work as expected with the open coded divide function: even if the do_div we are using doesn't have a constant divisor, the compiler still includes the else parts of the optimized do_div macro, and translates the divisions there to use __aeabi_uldivmod, instead of only calling __do_div_asm -> __do_div64 and optimizing/removing everything else out. So to reproduce, gcc 4.6 plus CONFIG_DEBUG_SECTION_MISMATCH=y and CONFIG_MTD_NAND_NANDSIM=m should do it, building on armel. After this change, the compiler does the intended thing even with -fno-inline-functions-called-once, and optimizes out as expected the constant handling in the optimized do_div on arm. As this also avoids a build issue, I'm marking for Stable, as I think is applicable for this case. Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com> Cc: stable@vger.kernel.org Acked-by: Nicolas Pitre <nico@linaro.org> Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Diffstat (limited to 'Documentation/DocBook/media')
0 files changed, 0 insertions, 0 deletions