From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966524AbbLPSX2 (ORCPT ); Wed, 16 Dec 2015 13:23:28 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:49528 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966306AbbLPRjy (ORCPT ); Wed, 16 Dec 2015 12:39:54 -0500 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Bhuvanchandra DV , Jonathan Cameron , Kamal Mostafa Subject: [PATCH 3.19.y-ckt 001/128] vf610_adc: Fix internal temperature calculation Date: Wed, 16 Dec 2015 09:37:21 -0800 Message-Id: <1450287568-19808-2-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1450287568-19808-1-git-send-email-kamal@canonical.com> References: <1450287568-19808-1-git-send-email-kamal@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Extended-Stable: 3.19 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.19.8-ckt12 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Bhuvanchandra DV commit 6219f432ec037317a77c40910da12a626c34af1c upstream. Calculate ADCR_VTEMP25 using VTEMP25 at VREFH_ADC 3V3. Existing calculations consider the typical values provided in datasheet. Those typical values are valid for VREFH_ADC at 3.0V. VTEMP25 is different for different VREFH_ADC voltages. With VREFH_ADC at 3.3V, voltage at 25°C is 0.699V. Hence update the VTEMP25 to 0.699V which gives ADCR@Temp25 as 867. Formula for finding ADCR@Temp25: ADCR@Temp25 = (ADCR@Vdd * V@TEMP25 * 10) / VDDconv ADCR@Vdd for 12-Bit ADC = 4095 VDDconv = VREFH_ADC * 10 VREFH_ADC@3.3V ADCR@Temp25 = (4095 * .699 * 10) / 33 ADCR@Temp25 ~= 867 | VREFH_ADC | V@TEMP25 | VDDconv | ADCR@Temp25 | | 3.0V | 0.696mV | 30 | 950 | | 3.3V | 0.699mV | 33 | 867 | Signed-off-by: Bhuvanchandra DV Acked-by: Fugang Duan Signed-off-by: Jonathan Cameron Signed-off-by: Kamal Mostafa --- drivers/iio/adc/vf610_adc.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/drivers/iio/adc/vf610_adc.c b/drivers/iio/adc/vf610_adc.c index 60617ed..cf56404 100644 --- a/drivers/iio/adc/vf610_adc.c +++ b/drivers/iio/adc/vf610_adc.c @@ -98,6 +98,13 @@ #define VF610_ADC_CALF 0x2 #define VF610_ADC_TIMEOUT msecs_to_jiffies(100) +/* V at 25°C of 696 mV */ +#define VF610_VTEMP25_3V0 950 +/* V at 25°C of 699 mV */ +#define VF610_VTEMP25_3V3 867 +/* Typical sensor slope coefficient at all temperatures */ +#define VF610_TEMP_SLOPE_COEFF 1840 + enum clk_sel { VF610_ADCIOC_BUSCLK_SET, VF610_ADCIOC_ALTCLK_SET, @@ -513,11 +520,13 @@ static int vf610_read_raw(struct iio_dev *indio_dev, break; case IIO_TEMP: /* - * Calculate in degree Celsius times 1000 - * Using sensor slope of 1.84 mV/°C and - * V at 25°C of 696 mV - */ - *val = 25000 - ((int)info->value - 864) * 1000000 / 1840; + * Calculate in degree Celsius times 1000 + * Using the typical sensor slope of 1.84 mV/°C + * and VREFH_ADC at 3.3V, V at 25°C of 699 mV + */ + *val = 25000 - ((int)info->value - VF610_VTEMP25_3V3) * + 1000000 / VF610_TEMP_SLOPE_COEFF; + break; default: mutex_unlock(&indio_dev->mlock); -- 1.9.1