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authorHerton Ronaldo Krzesinski <herton.krzesinski@canonical.com>2012-05-16 21:21:52 +0200
committerDavid Woodhouse <David.Woodhouse@intel.com>2012-07-06 17:59:33 +0200
commit596fd46268634082314b3af1ded4612e1b7f3f03 (patch)
treeeaec1116cfc24d25b54912dcd71f34f761f74491 /drivers
parentmtd: ABI documentation: clarification of bitflip_threshold (diff)
downloadlinux-596fd46268634082314b3af1ded4612e1b7f3f03.tar.xz
linux-596fd46268634082314b3af1ded4612e1b7f3f03.zip
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 'drivers')
-rw-r--r--drivers/mtd/nand/nandsim.c12
1 files changed, 3 insertions, 9 deletions
diff --git a/drivers/mtd/nand/nandsim.c b/drivers/mtd/nand/nandsim.c
index 6cc8fbfabb8e..cf0cd3146817 100644
--- a/drivers/mtd/nand/nandsim.c
+++ b/drivers/mtd/nand/nandsim.c
@@ -28,7 +28,7 @@
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/vmalloc.h>
-#include <asm/div64.h>
+#include <linux/math64.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/string.h>
@@ -546,12 +546,6 @@ static char *get_partition_name(int i)
return kstrdup(buf, GFP_KERNEL);
}
-static uint64_t divide(uint64_t n, uint32_t d)
-{
- do_div(n, d);
- return n;
-}
-
/*
* Initialize the nandsim structure.
*
@@ -580,7 +574,7 @@ static int init_nandsim(struct mtd_info *mtd)
ns->geom.oobsz = mtd->oobsize;
ns->geom.secsz = mtd->erasesize;
ns->geom.pgszoob = ns->geom.pgsz + ns->geom.oobsz;
- ns->geom.pgnum = divide(ns->geom.totsz, ns->geom.pgsz);
+ ns->geom.pgnum = div_u64(ns->geom.totsz, ns->geom.pgsz);
ns->geom.totszoob = ns->geom.totsz + (uint64_t)ns->geom.pgnum * ns->geom.oobsz;
ns->geom.secshift = ffs(ns->geom.secsz) - 1;
ns->geom.pgshift = chip->page_shift;
@@ -921,7 +915,7 @@ static int setup_wear_reporting(struct mtd_info *mtd)
if (!rptwear)
return 0;
- wear_eb_count = divide(mtd->size, mtd->erasesize);
+ wear_eb_count = div_u64(mtd->size, mtd->erasesize);
mem = wear_eb_count * sizeof(unsigned long);
if (mem / sizeof(unsigned long) != wear_eb_count) {
NS_ERR("Too many erase blocks for wear reporting\n");