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From: Liam Beguin <liambeguin@gmail.com>
To: liambeguin@gmail.com, peda@axentia.se, jic23@kernel.org,
	lars@metafoo.de, pmeerw@pmeerw.net
Cc: linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org,
	devicetree@vger.kernel.org, robh+dt@kernel.org
Subject: [PATCH v6 09/13] iio: afe: rescale: fix precision on fractional log scale
Date: Tue, 20 Jul 2021 23:06:09 -0400	[thread overview]
Message-ID: <20210721030613.3105327-10-liambeguin@gmail.com> (raw)
In-Reply-To: <20210721030613.3105327-1-liambeguin@gmail.com>

From: Liam Beguin <lvb@xiphos.com>

The IIO_VAL_FRACTIONAL_LOG2 scale type doesn't return the expected
scale. Update the case so that the rescaler returns a fractional type
and a more precise scale.

Signed-off-by: Liam Beguin <lvb@xiphos.com>
---
 drivers/iio/afe/iio-rescale.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index 35fa3b4e53e0..47cd4a6d9aca 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -44,12 +44,9 @@ int rescale_process_scale(struct rescale *rescale, int scale_type,
 		*val2 = rescale->denominator;
 		return IIO_VAL_FRACTIONAL;
 	case IIO_VAL_FRACTIONAL_LOG2:
-		tmp = *val * 1000000000LL;
-		do_div(tmp, rescale->denominator);
-		tmp *= rescale->numerator;
-		do_div(tmp, 1000000000LL);
-		*val = tmp;
-		return scale_type;
+		*val = rescale->numerator * *val;
+		*val2 = rescale->denominator * (1 << *val2);
+		return IIO_VAL_FRACTIONAL;
 	case IIO_VAL_INT_PLUS_NANO:
 		tmp = ((s64)*val * 1000000000LL + *val2) * rescale->numerator;
 		tmp = div_s64(tmp, rescale->denominator);
-- 
2.30.1.489.g328c10930387


  parent reply	other threads:[~2021-07-21  3:13 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-21  3:06 [PATCH v6 00/13] iio: afe: add temperature rescaling support Liam Beguin
2021-07-21  3:06 ` [PATCH v6 01/13] iio: inkern: apply consumer scale on IIO_VAL_INT cases Liam Beguin
2021-07-21  3:06 ` [PATCH v6 02/13] iio: inkern: apply consumer scale when no channel scale is available Liam Beguin
2021-07-21  3:06 ` [PATCH v6 03/13] iio: inkern: make a best effort on offset calculation Liam Beguin
2021-07-21  3:06 ` [PATCH v6 04/13] iio: afe: rescale: expose scale processing function Liam Beguin
2021-07-21  3:06 ` [PATCH v6 05/13] iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support Liam Beguin
2021-07-23 21:16   ` Peter Rosin
2021-07-28  0:21     ` Liam Beguin
2021-07-28  7:19       ` Peter Rosin
2021-07-29 15:56         ` Liam Beguin
2021-07-30  6:49           ` Peter Rosin
2021-07-30  7:01             ` Peter Rosin
2021-07-30 20:01               ` Liam Beguin
2021-07-30 19:57             ` Liam Beguin
2021-07-31 17:47         ` Jonathan Cameron
2021-07-21  3:06 ` [PATCH v6 06/13] iio: afe: rescale: add offset support Liam Beguin
2021-07-21  3:06 ` [PATCH v6 07/13] iio: test: add basic tests for the iio-rescale driver Liam Beguin
2021-07-24  8:40   ` kernel test robot
2021-07-21  3:06 ` [PATCH v6 08/13] iio: afe: rescale: reduce risk of integer overflow Liam Beguin
2021-07-23 21:17   ` Peter Rosin
2021-07-28  0:07     ` Liam Beguin
2021-07-28  7:47       ` Peter Rosin
2021-07-29 16:02         ` Liam Beguin
2021-07-21  3:06 ` Liam Beguin [this message]
2021-07-23 21:20   ` [PATCH v6 09/13] iio: afe: rescale: fix precision on fractional log scale Peter Rosin
2021-07-28  0:26     ` Liam Beguin
2021-07-28  7:58       ` Peter Rosin
2021-07-29 16:19         ` Liam Beguin
2021-07-21  3:06 ` [PATCH v6 10/13] iio: afe: rescale: add RTD temperature sensor support Liam Beguin
2021-07-21  3:06 ` [PATCH v6 11/13] iio: afe: rescale: add temperature transducers Liam Beguin
2021-07-21  3:06 ` [PATCH v6 12/13] dt-bindings: iio: afe: add bindings for temperature-sense-rtd Liam Beguin
2021-07-21  3:06 ` [PATCH v6 13/13] dt-bindings: iio: afe: add bindings for temperature transducers Liam Beguin
2021-07-23 22:59   ` Rob Herring

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