This is a note to let you know that I've just added the patch titled
iio: gts-helper: Fix division loop
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
iio-gts-helper-fix-division-loop.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 9839aeafcba7a71a35cf22e3ae169505866001e0
Author: Matti Vaittinen <mazziesaccount@xxxxxxxxx>
Date: Mon Feb 12 13:20:09 2024 +0200
iio: gts-helper: Fix division loop
[ Upstream commit bb76cc45dcdfcd962a5994b8fe19ab74fc6c3c3a ]
The loop based 64bit division may run for a long time when dividend is a
lot bigger than the divider. Replace the division loop by the
div64_u64() which implementation may be significantly faster.
Tested-by: Subhajit Ghosh <subhajit.ghosh@xxxxxxxxxxxxxx>
Signed-off-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx>
Fixes: 38416c28e168 ("iio: light: Add gain-time-scale helpers")
Link: https://lore.kernel.org/r/Zcn-6e-0-nh2WcfU@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/iio/industrialio-gts-helper.c b/drivers/iio/industrialio-gts-helper.c
index 7653261d2dc2b..b51eb6cb766f3 100644
--- a/drivers/iio/industrialio-gts-helper.c
+++ b/drivers/iio/industrialio-gts-helper.c
@@ -34,24 +34,11 @@
static int iio_gts_get_gain(const u64 max, const u64 scale)
{
u64 full = max;
- int tmp = 1;
if (scale > full || !scale)
return -EINVAL;
- if (U64_MAX - full < scale) {
- /* Risk of overflow */
- if (full - scale < scale)
- return 1;
-
- full -= scale;
- tmp++;
- }
-
- while (full > scale * (u64)tmp)
- tmp++;
-
- return tmp;
+ return div64_u64(full, scale);
}
/**
