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.
Signed-off-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx>
Fixes: 38416c28e168 ("iio: light: Add gain-time-scale helpers")
---
This change was earlier applied and reverted as it confusingly lacked of
the removal of the overflow check (which is only needed when we do
looping "while (full > scale * (u64)tmp)". As this loop got removed, the
check got also obsolete and leaving it to the code caused some
confusion.
So, I marked this as a v2, where v1 is the reverted change discussed
here:
https://lore.kernel.org/linux-iio/ZZZ7pJBGkTdFFqiY@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
Revision history:
v1 => v2:
- Drop the obsolete overflow check
- Rebased on top of the v6.8-rc1
iio: gts: loop fix fix
---
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 7653261d2dc2..b51eb6cb766f 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);
}
/**
base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d
--
2.43.0
--
Matti Vaittinen, Linux device drivers
ROHM Semiconductors, Finland SWDC
Kiviharjunlenkki 1E
90220 OULU
FINLAND
~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~
Simon says - in Latin please.
~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~
Thanks to Simon Glass for the translation =]
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