From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 24612946F for ; Sat, 25 Nov 2023 15:14:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="L01tF9Jf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 663BCC433C7; Sat, 25 Nov 2023 15:14:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1700925296; bh=g4MRYZCrwAzR4gcbAiWJD+UTGWXSA2J1PohiCLNeqRQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=L01tF9JfXbr/AXBVcy7UX+7F5ZQi7wKMcDoDw9icfrYuion+xOdd5XFSoQmGnUEwd bGeVQKvJMvI/Fs7dW532kqPBwGTvVhUnZDCs2i4GfTPXJr1Tvhy5vNhKEMPs29enRe r6Vx6StolVibVWQ4Ltq1HMVfcm/0EpPmXIFzzq84zIVmn7glZ4LrJn6SKRgOIZysV2 YCA6e0FFlQOltot57WjUO59KocIqtybXlwyba6nj4/eDGFwoWsnI8h4utvgVbBYB3K k8janE1/fR1viAXR/iffqKc/GrLkY9R1cPtaJAL5V2d/hP9AtlIFfPdBjY//0ugneP v0trWH2z1cTwQ== Date: Sat, 25 Nov 2023 15:14:49 +0000 From: Jonathan Cameron To: Javier Carrasco Cc: Gerald Loacker , Lars-Peter Clausen , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] iio: tmag5273: fix temperature offset Message-ID: <20231125151449.42f2f2ed@jic23-huawei> In-Reply-To: <9879beec-05fc-4fc6-af62-d771e238954e@wolfvision.net> References: <9879beec-05fc-4fc6-af62-d771e238954e@wolfvision.net> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-iio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 21 Nov 2023 06:48:39 +0100 Javier Carrasco wrote: > The current offset has the scale already applied to it. The ABI > documentation defines the offset parameter as "offset to be added > to [Y]_raw prior to scaling by [Y]_scale in order to > obtain value in the units as specified in [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 Applied to the fixes-togreg branch of iio.git and marked for stable. Thanks, Jonathan > --- > 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,