Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:2 as permitted sender) client-ip=2620:137:e000::3:2;
Message-ID: <9879beec-05fc-4fc6-af62-d771e238954e@wolfvision.net>
Date:   Tue, 21 Nov 2023 06:48:39 +0100
User-Agent: Mozilla Thunderbird
From:   Javier Carrasco <javier.carrasco@wolfvision.net>
Subject: [PATCH v2] iio: tmag5273: fix temperature offset
To:     Gerald Loacker <gerald.loacker@wolfvision.net>,
        Jonathan Cameron <jic23@kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>
Cc:     linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org,
        Javier Carrasco <javier.carrasco@wolfvision.net>
Content-Language: en-US
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?cjU5TVFwVHF3bjVBSXNPbmhzMGUrYUJKU1RKWFljMEpob1VNaFVsaWNFcFE5?=
 =?utf-8?B?UXZWWjRyOTU3WDRpakxmMGdRS1NQTWtvSnBWQ3NMSlM1eHNQNDJpYThDYVhw?=
 =?utf-8?B?N2Z2SXJQRjVVRk53cHNrOFo0QmYyMGZvYVR1UmZGK1h2V0xjSS9KajB3OWY5?=
 =?utf-8?B?R1l6d1JyMkltdS9CRVgxOVRyZGhmY2NPTW5BbTBRbjZ3N0pNQnlWSEgwODJC?=
 =?utf-8?B?N1VBaUhCRkFyUnlQQk52dUw1SzJ2RnZhTi9udjBlRklVZndWTys4UUlCa3dX?=
 =?utf-8?B?OGFCVkx2TnBFRU42SEJ4cTc5L2tXSm5xVEhUdFNmQW1SV3J0TFhVZDZuTGZm?=
 =?utf-8?B?eWdCNFJPVkpSMnpHWWhYYVl1QXA4ckJQaEo0OC9CS3d5bEJwZWk3NHltT0JJ?=
 =?utf-8?B?djM2RXhkalNtdzV3ZTcrK3RwRGRmMU5oVW9VNEw3QUFhRndyNVRPT2Yyb1Jv?=
 =?utf-8?B?U0hFZ1ViTUdPRlZSczlqM2VvQ0xyaUduR09WWjVFS29HOWhFeWoxZFhWbnN4?=
 =?utf-8?B?STlLK012RFYybjN5a29RU2l5bWtHNzFzK3FuRDV1QmpzWkIyYmNVVlEweGZj?=
 =?utf-8?B?OWpVckxFL01ObkpiUk5abTJEYWVNekVrRVZsODhOcTUrSUR2S2haWWZnSG9v?=
 =?utf-8?B?MGNjTm0yMHdIbkg5UTZJdGIxOFhXYk1jL2phdWd3YzJtRi9tejduRFJTeTdJ?=
 =?utf-8?B?NFV3NU1ZNklXSi92WEliMWV6YmJ6YnlTdWpWTGZ6UmZ5UXRKWEpCMWI1YVJ4?=
 =?utf-8?B?T3R1TkF5TlR6OGF5MWpldjZzRUxoQXhHNGdBWGVOVjA3bERudVczM1FhK3ZX?=
 =?utf-8?B?R1dHV08xT3JSL3BPYWtoZ2VTck8wNXBaSUFUR2txRW9PdzRUUFMzd0xWd1NC?=
 =?utf-8?B?UEFsVTV3VDNwSHNkcFRqcmVXelFnVStrdGtmRVF3ejV4bDV5UmRLZVJ6cWNQ?=
 =?utf-8?B?RkNHalppeWZHN2FJUXZyem5PclZnT0M4WHc1aG5lU2h6SCtlRUdYYzBwbit3?=
 =?utf-8?B?ZkExTmVvQ3k3OWdMUFRoZjZTaU5XdlBSMW1FQ016a3kyRmFZZllvMnFidVdO?=
 =?utf-8?B?eUY3aUxva1pkZVNaY1NUY2gra09oRm1paVRwMGVHaGlpTUVqYUlYcVBUNWRm?=
 =?utf-8?B?YWFDc0tZaGswWC8vZ3E3OVNuTTMwTEVvcjZNcE0xbFlHWnBKcjM4WkdCQldR?=
 =?utf-8?B?a0tmdmpKd2M3TjV3amJzM21IMWkxQ3kxMm5KSnNHRjd1SEJyT1BjNEZHcWhw?=
 =?utf-8?B?MzVGSjU1SWpzaUlyYVhwRnZJV1BjT2dtd2tRcGRWT09UNzF3K3NsZ25Qd1V1?=
 =?utf-8?B?WDRCY3RzRTZiZC9TUyt4RmYybXRJWHh2R2xQZlRPZWFKbHhrSnozdmp5dW1X?=
 =?utf-8?B?RnhSMFpVRjVwUi9MQnI2cjhxeFJVdFdtRkVNMEc4c0FyWkhtZHhwM0N4ZHBD?=
 =?utf-8?B?YlRybndkcFgwWHdkMFF4c3J0eVBLNVhmVFE5SStDRTZUcllJRDRGRmFEQmda?=
 =?utf-8?B?UjNXUGFpMmo2anphZjFSNU53dU1rKzZXYTVLT2x2S2x4ZFM5Y0k5SUkrZ2gr?=
 =?utf-8?B?K1dYWHFUaThzNVZLZWg5WDBSaEFudUhhR1RKMy9Kek9acjNHYlBaOUZUaG9I?=
 =?utf-8?B?eWNaQy9uU09NRklDM2ZHWFlNcnZxOUcvQ3d5bDJxN3pvTllJQnBHSTRUczgr?=
 =?utf-8?B?QkJxQUxjN3VLMEhHVTJJcDJEYnVKMzZsQ0N4RUx5cEdDZGdGUWEySy92M0tm?=
 =?utf-8?B?b0tORS9HSWc5OEd5Y2o2bnZQUDlpTGFEWmpMd1doVmEvNkIvZnFwVGt4akZh?=
 =?utf-8?B?UWF2RUtLekpDdUZhbGRoUFk1N3FnSldyKzdxdFVXNWZJRk1NMC9LNCsvclhs?=
 =?utf-8?B?UGRNR29RQXU4MzArR1V1WVNpMWJPUU1PcklGNmRWOE92aFA5dDgxUVVaaVVU?=
 =?utf-8?B?VnBnRkhGeVZ0R0p4TStOTmtiaVJFWjd3dU5VWEQycTBQZThXdThrc2p0WmZC?=
 =?utf-8?B?RWJJMEh4OVI1QkM2Y0QwQkRIU29aTTgyQmR3MHJ2Q2pHOWphOHNrcTAxM0NQ?=
 =?utf-8?B?RFJOc2M4QUlHOUZUTEUvM2dHYVRuOUJ0UmhpUFp3NERCT0NCQ3I5L0NySXJ2?=
 =?utf-8?B?dFByN2h5ZExPMHJJdVNmM1VBK0FaL3kwM2ZtVTRUR2NNZnVaT1BJaCtJczRH?=
 =?utf-8?Q?9rA2xZoTOgupRI1QSntc7TU=3D?=
X-OriginatorOrg: wolfvision.net
X-MS-Exchange-CrossTenant-Network-Message-Id: f10d922e-e85e-4793-f97b-08dbea558408
X-MS-Exchange-CrossTenant-AuthSource: VE1PR08MB4974.eurprd08.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Nov 2023 05:48:41.3050
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: e94ec9da-9183-471e-83b3-51baa8eb804f
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: ja+1PqiI8V1K5quIJrHQGH35PmfmJSelSsB8ZlaAiRoBCNzgMpROdfRtKDzKiWk8WCX9MVzNlHPT+l1gFOz9UNOUkjGg5OncTZYeJOPUcKI=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM8PR08MB5795
X-Spam-Status: No, score=-0.9 required=5.0 tests=DKIM_SIGNED,DKIM_VALID,
	DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,
	SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable
	autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on agentk.vger.email
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (agentk.vger.email [0.0.0.0]); Mon, 20 Nov 2023 21:48:58 -0800 (PST)

The current offset has the scale already applied to it. The ABI
documentation defines the offset parameter as "offset to be added
to <type>[Y]_raw prior to scaling by <type>[Y]_scale in order to
obtain value in the <type> units as specified in <type>[Y]_raw
documentation"

The right value is obtained at 0 degrees Celsius by the formula provided
in the datasheet:

T = Tsens_t0 + (Tadc_t - Tadc_t0) / Tadc_res

where:
T = 0 degrees Celsius
Tsens_t0 (reference temperature) = 25 degrees Celsius
Tadc_t0 (16-bit format for Tsens_t0) = 17508
Tadc_res = 60.1 LSB/degree Celsius

The resulting offset is 16005.5, which has been truncated to 16005 to
provide an integer value with a precision loss smaller than the 1-LSB
measurement precision.

Fix the offset to apply its value prior to scaling.

Signed-off-by: Javier Carrasco <javier.carrasco@wolfvision.net>
---
Changes in v2:
- Fixed typo in the offset value (16005 instead of 16605) (Jonathan Cameron)

- Link to v1:
https://lore.kernel.org/r/20231023-topic-tmag5273x1_temp_offset-v1-1-983dca43292c@wolfvision.net
---
 drivers/iio/magnetometer/tmag5273.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iio/magnetometer/tmag5273.c
b/drivers/iio/magnetometer/tmag5273.c
index c5e5c4ad681e..e8c4ca142d21 100644
--- a/drivers/iio/magnetometer/tmag5273.c
+++ b/drivers/iio/magnetometer/tmag5273.c
@@ -356,7 +356,7 @@ static int tmag5273_read_raw(struct iio_dev *indio_dev,
 	case IIO_CHAN_INFO_OFFSET:
 		switch (chan->type) {
 		case IIO_TEMP:
-			*val = -266314;
+			*val = -16005;
 			return IIO_VAL_INT;
 		default:
 			return -EINVAL;

---
base-commit: 05d3ef8bba77c1b5f98d941d8b2d4aeab8118ef1
change-id: 20231023-topic-tmag5273x1_temp_offset-17774cbce961

Best regards,
-- 
Javier Carrasco <javier.carrasco@wolfvision.net>