linux-kernel - Re: [PATCH] iio: gts-helper: Fix division loop

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Message-ID: <9f94a3de-7f04-4ad8-9b98-9e6312cce589@tweaklogic.com>
Date: Mon, 5 Feb 2024 00:19:14 +1030
From: Subhajit Ghosh <subhajit.ghosh@...aklogic.com>
To: Matti Vaittinen <mazziesaccount@...il.com>,
 Jonathan Cameron <jic23@...nel.org>
Cc: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
 Lars-Peter Clausen <lars@...afoo.de>, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: gts-helper: Fix division loop

Hi Matti,
>>>>>   drivers/iio/industrialio-gts-helper.c | 5 ++---
>>>>>   1 file changed, 2 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/drivers/iio/industrialio-gts-helper.c b/drivers/iio/industrialio-gts-helper.c
>>>>> index 7653261d2dc2..abcab2d38589 100644
>>>>> --- a/drivers/iio/industrialio-gts-helper.c
>>>>> +++ b/drivers/iio/industrialio-gts-helper.c
>>>>> @@ -34,7 +34,7 @@
>>>>>   static int iio_gts_get_gain(const u64 max, const u64 scale)
>>>>>   {
>>>>>       u64 full = max;
>>>>> -    int tmp = 1;
>>>>> +    int tmp = 0;
>>>>>       if (scale > full || !scale)
>>>>>           return -EINVAL;
>>>>> @@ -48,8 +48,7 @@ static int iio_gts_get_gain(const u64 max, const u64 scale)
>>>>>           tmp++;
>>>>>       }
>>>>> -    while (full > scale * (u64)tmp)
>>>>> -        tmp++;
>>>>> +    tmp += div64_u64(full, scale);
>>>>>       return tmp;
>>>>>   }
>>>>>
>>>>> base-commit: 2cc14f52aeb78ce3f29677c2de1f06c0e91471ab
>>>>
>>>>
>>> Hi Matti,
>>>
>>> Your fix works beautifully with the latest version of apds9306 driver which I am working on.
>>> All available scale values can be set without any errors. Thank you.
>>
>> Thanks for testing Subhajit! Just to ensure we have no miscommunication - did you test just this division fix, or the rounding fix here:
>> https://lore.kernel.org/lkml/37d3aa193e69577353d314e94463a08d488ddd8d.1701780964.git.mazziesaccount@gmail.com/
> You are most welcome. I did not check the above rounding fix pointed out by the link. I will be happy to check it and let you know by the end of this month.
> I checked this division fix.
I tested the patch in the above link with adps9306 driver which I am working on and it seems to work well without any issues.

Regards,
Subhajit Ghosh