From patchwork Fri Nov 6 10:18:25 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexandru Ardelean X-Patchwork-Id: 11886753 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 799426A2 for ; Fri, 6 Nov 2020 10:18:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F30D206CB for ; Fri, 6 Nov 2020 10:18:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726954AbgKFKSy (ORCPT ); Fri, 6 Nov 2020 05:18:54 -0500 Received: from mx0a-00128a01.pphosted.com ([148.163.135.77]:47794 "EHLO mx0a-00128a01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726124AbgKFKSw (ORCPT ); Fri, 6 Nov 2020 05:18:52 -0500 Received: from pps.filterd (m0167088.ppops.net [127.0.0.1]) by mx0a-00128a01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 0A6AEe3P019359; Fri, 6 Nov 2020 05:18:36 -0500 Received: from nwd2mta4.analog.com ([137.71.173.58]) by mx0a-00128a01.pphosted.com with ESMTP id 34h1s5d0n0-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 06 Nov 2020 05:18:36 -0500 Received: from ASHBMBX9.ad.analog.com (ashbmbx9.ad.analog.com [10.64.17.10]) by nwd2mta4.analog.com (8.14.7/8.14.7) with ESMTP id 0A6AIZUE006277 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=FAIL); Fri, 6 Nov 2020 05:18:35 -0500 Received: from ASHBCASHYB4.ad.analog.com (10.64.17.132) by ASHBMBX9.ad.analog.com (10.64.17.10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1779.2; Fri, 6 Nov 2020 05:18:34 -0500 Received: from ASHBMBX9.ad.analog.com (10.64.17.10) by ASHBCASHYB4.ad.analog.com (10.64.17.132) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1779.2; Fri, 6 Nov 2020 05:18:33 -0500 Received: from zeus.spd.analog.com (10.66.68.11) by ASHBMBX9.ad.analog.com (10.64.17.10) with Microsoft SMTP Server id 15.1.1779.2 via Frontend Transport; Fri, 6 Nov 2020 05:18:33 -0500 Received: from saturn.ad.analog.com ([10.48.65.107]) by zeus.spd.analog.com (8.15.1/8.15.1) with ESMTP id 0A6AISTQ016474; Fri, 6 Nov 2020 05:18:31 -0500 From: Alexandru Ardelean To: , CC: , , , , Alexandru Ardelean Subject: [PATCH 3/3] hwmon: (ltc2945): add support for sense resistor Date: Fri, 6 Nov 2020 12:18:25 +0200 Message-ID: <20201106101825.30960-3-alexandru.ardelean@analog.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20201106101825.30960-1-alexandru.ardelean@analog.com> References: <20201106101825.30960-1-alexandru.ardelean@analog.com> MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-11-06_03:2020-11-05,2020-11-06 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 priorityscore=1501 mlxlogscore=999 clxscore=1015 bulkscore=0 spamscore=0 adultscore=0 suspectscore=0 phishscore=0 impostorscore=0 lowpriorityscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011060073 Precedence: bulk List-ID: X-Mailing-List: linux-hwmon@vger.kernel.org The sense resistor is a parameter of the board. It should be configured in the driver via a device-tree / ACPI property, so that the proper current measurements can be done in the driver. It shouldn't be necessary that userspace need to know about the value of the resistor. It makes things a bit harder to make the application code portable from one board to another. This change implements support for the sense resistor to be configured from DT/ACPI and used in current calculations. Signed-off-by: Alexandru Ardelean --- drivers/hwmon/ltc2945.c | 48 ++++++++++++++++++----------------------- 1 file changed, 21 insertions(+), 27 deletions(-) diff --git a/drivers/hwmon/ltc2945.c b/drivers/hwmon/ltc2945.c index 75d997d31e01..500401a82c49 100644 --- a/drivers/hwmon/ltc2945.c +++ b/drivers/hwmon/ltc2945.c @@ -61,9 +61,11 @@ /** * struct ltc2945_state - driver instance specific data * @regmap regmap object to access device registers + * @r_sense_uohm current sense resistor value */ struct ltc2945_state { struct regmap *regmap; + u32 r_sense_uohm; }; static inline bool is_power_reg(u8 reg) @@ -101,9 +103,8 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg) case LTC2945_MAX_POWER_THRES_H: case LTC2945_MIN_POWER_THRES_H: /* - * Convert to uW by assuming current is measured with - * an 1mOhm sense resistor, similar to current - * measurements. + * Convert to uW by and scale it with the configured + * sense resistor, similar to current measurements. * Control register bit 0 selects if voltage at SENSE+/VDD * or voltage at ADIN is used to measure power. */ @@ -112,10 +113,10 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg) return ret; if (control & CONTROL_MULT_SELECT) { /* 25 mV * 25 uV = 0.625 uV resolution. */ - val *= 625LL; + val = DIV_ROUND_CLOSEST_ULL(val * 625LL * 1000, st->r_sense_uohm); } else { /* 0.5 mV * 25 uV = 0.0125 uV resolution. */ - val = (val * 25LL) >> 1; + val = DIV_ROUND_CLOSEST_ULL(val * 25LL * 1000, st->r_sense_uohm) >> 1; } break; case LTC2945_VIN_H: @@ -140,13 +141,10 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg) case LTC2945_MAX_SENSE_THRES_H: case LTC2945_MIN_SENSE_THRES_H: /* - * 25 uV resolution. Convert to current as measured with - * an 1 mOhm sense resistor, in mA. If a different sense - * resistor is installed, calculate the actual current by - * dividing the reported current by the sense resistor value - * in mOhm. + * 25 uV resolution. Convert to current and scale it + * with the value of the sense resistor. */ - val *= 25; + val = DIV_ROUND_CLOSEST_ULL(val * 25 * 1000, st->r_sense_uohm); break; default: return -EINVAL; @@ -169,9 +167,8 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg, case LTC2945_MAX_POWER_THRES_H: case LTC2945_MIN_POWER_THRES_H: /* - * Convert to register value by assuming current is measured - * with an 1mOhm sense resistor, similar to current - * measurements. + * Convert to register value, scale it with the configured sense + * resistor value, similar to current measurements. * Control register bit 0 selects if voltage at SENSE+/VDD * or voltage at ADIN is used to measure power, which in turn * determines register calculations. @@ -181,14 +178,10 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg, return ret; if (control & CONTROL_MULT_SELECT) { /* 25 mV * 25 uV = 0.625 uV resolution. */ - val = DIV_ROUND_CLOSEST_ULL(val, 625); + val = DIV_ROUND_CLOSEST_ULL(val * 1000, 625 * st->r_sense_uohm); } else { - /* - * 0.5 mV * 25 uV = 0.0125 uV resolution. - * Divide first to avoid overflow; - * accept loss of accuracy. - */ - val = DIV_ROUND_CLOSEST_ULL(val, 25) * 2; + /* 0.5 mV * 25 uV = 0.0125 uV resolution. */ + val = DIV_ROUND_CLOSEST_ULL(val * 2 * 1000, 25 * st->r_sense_uohm); } break; case LTC2945_VIN_H: @@ -213,13 +206,10 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg, case LTC2945_MAX_SENSE_THRES_H: case LTC2945_MIN_SENSE_THRES_H: /* - * 25 uV resolution. Convert to current as measured with - * an 1 mOhm sense resistor, in mA. If a different sense - * resistor is installed, calculate the actual current by - * dividing the reported current by the sense resistor value - * in mOhm. + * 25 uV resolution. Convert to current and scale it + * with the value of the sense resistor, in mA. */ - val = DIV_ROUND_CLOSEST_ULL(val, 25); + val = DIV_ROUND_CLOSEST_ULL(val * 1000, 25 * st->r_sense_uohm); break; default: return -EINVAL; @@ -475,6 +465,10 @@ static int ltc2945_probe(struct i2c_client *client) return PTR_ERR(regmap); } + if (device_property_read_u32(dev, "shunt-resistor-micro-ohms", + &st->r_sense_uohm)) + st->r_sense_uohm = 1000; + st->regmap = regmap; /* Clear faults */