From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3ACE0C433E0 for ; Thu, 7 Jan 2021 15:26:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DFD2923403 for ; Thu, 7 Jan 2021 15:26:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728114AbhAGP0X (ORCPT ); Thu, 7 Jan 2021 10:26:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36886 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727749AbhAGP0W (ORCPT ); Thu, 7 Jan 2021 10:26:22 -0500 Received: from mail-oo1-xc2e.google.com (mail-oo1-xc2e.google.com [IPv6:2607:f8b0:4864:20::c2e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DEB51C0612F4; Thu, 7 Jan 2021 07:25:41 -0800 (PST) Received: by mail-oo1-xc2e.google.com with SMTP id j21so1638438oou.11; Thu, 07 Jan 2021 07:25:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=qHozb/E6JfCKzfGCGapqQNL16pfKAvjUhqi2FLGmly8=; b=RoocLYvV6QiLFocPwQhISy0TqKPPs1bP2GCBu8ThmDcox0VpNTAgEe/cqXTIXKau9F a8DYGbmI3OAJ0JXbLdEuHTX1hRzMDkyMdWxeRmF+2/2yb0Kg4JUgwWo0py9kZyc7QZ84 SempakJXEwdWPPgl2KoCEt+G/kwxLNLarlbDRh56D/qZenIlWnI7yERGYnAAVJWTUY9O WYiR7PuU7u8r4h7SELkPFZMp//i539XNCQ8+FhmK2n90D7h3jMJ1TZqg8BZixRGWv/N3 7u4R08062BrIFRSxR5EuNedw/OK4LMM18zmktDvwOo9p03ddTXwz8f71PVVkLqjyHl0f nCPg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=qHozb/E6JfCKzfGCGapqQNL16pfKAvjUhqi2FLGmly8=; b=Y5cqCJ1qG/FHxzAlq6QQ6s24qgACmFrxak2AF9O6x5bY0ty5/8CcyVq7BllLRqxvUF CQln42K1l5iDqYFk3VdoFUMVyFS5dZ4kStP+xKEN6FDLSYfy/9YV5iw18qSaIsd9XF+m a0zNiAyY7tKMVVChSgmw0I82UXob0K/76t/xiyx3Y++vntksspchP9qzhJw1ZB5lssdy UeYb2Co89HitX8CIVUdSfATzY9vis2jB6n1CQz/6WmRJfmu1VNOAWpCV+Rex8E3P0OFS DysAUV4Dv4/wbJY7ES3Vhn4Okczaa/h7gpl4jRQjMCtRmCjFFZLTGu0ZAzOgd2k34KPV NkqQ== X-Gm-Message-State: AOAM531zUcJuHjYxjLc50uNDd6aOYKeIlpYzpkfE5fSW6ostnLXa29/v C+DJ3CzlXMU6qkGoaZHDOdk= X-Google-Smtp-Source: ABdhPJx9krEQiazaM+tHfpYNLxESgrKuMlHKWjtEeQ52NOZ4uss+miKLLxvahhoV5IL5Kn060GAgYA== X-Received: by 2002:a4a:e687:: with SMTP id u7mr1467255oot.20.1610033141202; Thu, 07 Jan 2021 07:25:41 -0800 (PST) Received: from localhost ([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id s24sm1351752oij.20.2021.01.07.07.25.39 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Thu, 07 Jan 2021 07:25:40 -0800 (PST) Sender: Guenter Roeck Date: Thu, 7 Jan 2021 07:25:38 -0800 From: Guenter Roeck To: Alexandru Ardelean Cc: linux-hwmon@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, robh+dt@kernel.org, jdelvare@suse.com, mark.thoren@analog.com, ardeleanalex@gmail.com Subject: Re: [PATCH v3 3/4] hwmon: (ltc2945): add support for sense resistor Message-ID: <20210107152538.GC13040@roeck-us.net> References: <20210107103417.16010-1-alexandru.ardelean@analog.com> <20210107103417.16010-4-alexandru.ardelean@analog.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210107103417.16010-4-alexandru.ardelean@analog.com> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-hwmon@vger.kernel.org On Thu, Jan 07, 2021 at 12:34:16PM +0200, Alexandru Ardelean wrote: > 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. > Also, the maximum power and current that can be represented by the driver > are scaled with the value of the sense resistor. > In a way you are correct, but that applies to all hwmon drivers, not just to this one. A solution which only applies to a single driver doesn't solve the underlying problem, which would be the desire or need to provide kernel-based scaling for hwmon drivers. As such, I am not inclined to accept this patch. We should think about a generic solution instead. Note that this patch doesn't compile on 32-bit targets. Thanks, Guenter > Signed-off-by: Alexandru Ardelean > --- > drivers/hwmon/ltc2945.c | 60 ++++++++++++++++++++++++++--------------- > 1 file changed, 39 insertions(+), 21 deletions(-) > > diff --git a/drivers/hwmon/ltc2945.c b/drivers/hwmon/ltc2945.c > index 41df2c8b7673..e60b15832b0e 100644 > --- a/drivers/hwmon/ltc2945.c > +++ b/drivers/hwmon/ltc2945.c > @@ -70,9 +70,15 @@ > /** > * struct ltc2945_state - driver instance specific data > * @regmap: regmap object to access device registers > + * @max_power_uw: maximum power that can be represented based on sense resistor > + * @max_current_ma: maximum current that can be represented based on sense resistor > + * @r_sense_mohm: current sense resistor value > */ > struct ltc2945_state { > struct regmap *regmap; > + u32 max_power_uw; > + u32 max_current_ma; > + u32 r_sense_mohm; > }; > > static inline bool is_power_reg(u8 reg) > @@ -110,9 +116,8 @@ 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. > */ > @@ -126,6 +131,7 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg) > /* 0.5 mV * 25 uV = 0.0125 uV resolution. */ > val = (val * 25LL) >> 1; > } > + val /= st->r_sense_mohm; > break; > case LTC2945_VIN_H: > case LTC2945_MAX_VIN_H: > @@ -149,13 +155,11 @@ 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 /= st->r_sense_mohm; > break; > default: > return -EINVAL; > @@ -163,7 +167,8 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg) > return val; > } > > -static unsigned long ltc2945_val_clamp(u8 reg, unsigned long val) > +static unsigned long ltc2945_val_clamp(struct ltc2945_state *st, u8 reg, > + unsigned long val) > { > switch (reg) { > case LTC2945_POWER_H: > @@ -171,8 +176,7 @@ static unsigned long ltc2945_val_clamp(u8 reg, unsigned long val) > case LTC2945_MIN_POWER_H: > case LTC2945_MAX_POWER_THRES_H: > case LTC2945_MIN_POWER_THRES_H: > - /* No sense in clamping now, LTC2945_POWER_FULL_SCALE_UW is larger than UINT32_MAX */ > - return val; > + return clamp_val(val, 0, st->max_power_uw); > case LTC2945_VIN_H: > case LTC2945_MAX_VIN_H: > case LTC2945_MIN_VIN_H: > @@ -190,7 +194,7 @@ static unsigned long ltc2945_val_clamp(u8 reg, unsigned long val) > case LTC2945_MIN_SENSE_H: > case LTC2945_MAX_SENSE_THRES_H: > case LTC2945_MIN_SENSE_THRES_H: > - return clamp_val(val, 0, LTC2945_SENSE_FULL_SCALE_MA); > + return clamp_val(val, 0, st->max_current_ma); > default: > /* > * This is unlikely to happen, and if it does, it should > @@ -215,9 +219,8 @@ 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. > @@ -236,6 +239,7 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg, > */ > val = DIV_ROUND_CLOSEST(val, 25) * 2; > } > + val *= st->r_sense_mohm; > break; > case LTC2945_VIN_H: > case LTC2945_MAX_VIN_H: > @@ -259,12 +263,10 @@ 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 *= st->r_sense_mohm; > val = DIV_ROUND_CLOSEST(val, 25); > break; > default: > @@ -303,7 +305,7 @@ static ssize_t ltc2945_value_store(struct device *dev, > if (ret) > return ret; > > - val = ltc2945_val_clamp(reg, val); > + val = ltc2945_val_clamp(st, reg, val); > > /* convert to register value, then clamp and write result */ > regval = ltc2945_val_to_reg(dev, reg, val); > @@ -512,6 +514,7 @@ static int ltc2945_probe(struct i2c_client *client) > struct ltc2945_state *st; > struct device *hwmon_dev; > struct regmap *regmap; > + u64 val64; > > st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL); > if (!st) > @@ -523,7 +526,22 @@ 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_mohm)) > + st->r_sense_mohm = 1000; > + > + if (st->r_sense_mohm < 1000) { > + dev_err(dev, "Value too small for sense resistor, minimum 1000\n"); > + return -EINVAL; > + } > + st->r_sense_mohm /= 1000; > + > st->regmap = regmap; > + val64 = LTC2945_POWER_FULL_SCALE_UW / st->r_sense_mohm; > + /* clamp power to ULONG_MAX, since we represent it on 32 bits */ > + st->max_power_uw = clamp_val(val64, 0, ULONG_MAX); > + > + st->max_current_ma = LTC2945_SENSE_FULL_SCALE_MA / st->r_sense_mohm; > > /* Clear faults */ > regmap_write(regmap, LTC2945_FAULT, 0x00); > -- > 2.17.1 >