mtd: nandsim: don't open code a do_div helper

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=596fd46268634082314b3af1ded4612e1b7f3f03
Commit:     596fd46268634082314b3af1ded4612e1b7f3f03
Parent:     021796b892dcad45743f3196e3eef7222870dd55
Author:     Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
AuthorDate: Wed May 16 16:21:52 2012 -0300
Committer:  David Woodhouse <David.Woodhouse at intel.com>
CommitDate: Fri Jul 6 16:59:33 2012 +0100

    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 at canonical.com>
    Cc: stable at vger.kernel.org
    Acked-by: Nicolas Pitre <nico at linaro.org>
    Signed-off-by: Artem Bityutskiy <artem.bityutskiy at linux.intel.com>
    Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
---
 drivers/mtd/nand/nandsim.c |   12 +++---------
 1 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/mtd/nand/nandsim.c b/drivers/mtd/nand/nandsim.c
index 6cc8fbf..cf0cd31 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");