From: Herton Ronaldo Krzesinski Date: Wed, 16 May 2012 19:21:52 +0000 (-0300) Subject: mtd: nandsim: don't open code a do_div helper X-Git-Tag: v3.5-rc7~17^2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=596fd46268634082314b3af1ded4612e1b7f3f03;p=pandora-kernel.git 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 Cc: stable@vger.kernel.org Acked-by: Nicolas Pitre Signed-off-by: Artem Bityutskiy Signed-off-by: David Woodhouse --- Reading git-diff-tree failed