[PATCH 6.6 566/638] iio: gts-helper: Fix division loop

Sasha Levin
2024-03-24T23:10:37Z

From: Matti Vaittinen <mazziesaccount@gmail.com>

[ 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@tweaklogic.com>
Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Fixes: 38416c28e168 ("iio: light: Add gain-time-scale helpers")
Link: https://lore.kernel.org/r/Zcn-6e-0-nh2WcfU@drtxq0yyyyyyyyyyyyyby-3.rev.dnainternet.fi
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/iio/industrialio-gts-helper.c | 15 +--------------
1 file changed, 1 insertion(+), 14 deletions(-)

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);
}

/**
--
2.43.0