[3.19.y-ckt stable] Patch "iio: mxs-lradc: Fix temperature offset" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    iio: mxs-lradc: Fix temperature offset

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt10.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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>From 48f4ec3fdc7cc234cb7068199c1200af2c686df2 Mon Sep 17 00:00:00 2001
From: Alexandre Belloni <alexandre.belloni at free-electrons.com>
Date: Wed, 7 Oct 2015 13:10:54 +0200
Subject: [PATCH 073/120] iio: mxs-lradc: Fix temperature offset
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit b94e22805a2224061bb263a82b72e09544a5fbb3 upstream.

0° Kelvin is actually −273.15°C, not -272.15°C. Fix the temperature offset.
Also improve the comment explaining the calculation.

Reported-by: Janusz Użycki <j.uzycki at elpromaelectronics.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni at free-electrons.com>
Acked-by: Stefan Wahren <stefan.wahren at i2se.com>
Acked-by: Marek Vasut <marex at denx.de>
Signed-off-by: Jonathan Cameron <jic23 at kernel.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/staging/iio/adc/mxs-lradc.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/iio/adc/mxs-lradc.c b/drivers/staging/iio/adc/mxs-lradc.c
index 351339c..3b9859b 100644
--- a/drivers/staging/iio/adc/mxs-lradc.c
+++ b/drivers/staging/iio/adc/mxs-lradc.c
@@ -912,11 +912,12 @@ static int mxs_lradc_read_raw(struct iio_dev *iio_dev,
 	case IIO_CHAN_INFO_OFFSET:
 		if (chan->type == IIO_TEMP) {
 			/* The calculated value from the ADC is in Kelvin, we
-			 * want Celsius for hwmon so the offset is
-			 * -272.15 * scale
+			 * want Celsius for hwmon so the offset is -273.15
+			 * The offset is applied before scaling so it is
+			 * actually -213.15 * 4 / 1.012 = -1079.644268
 			 */
-			*val = -1075;
-			*val2 = 691699;
+			*val = -1079;
+			*val2 = 644268;

 			return IIO_VAL_INT_PLUS_MICRO;
 		}
--
1.9.1