From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x224v4zSWRiIMCrZqWGQT9p8wyTdxMteJG7l8TisbmBlCLBswDckPoIsl6xBw7Llwtf/UkOZF ARC-Seal: i=1; a=rsa-sha256; t=1519197342; cv=none; d=google.com; s=arc-20160816; b=FjE5t6z09j68EPfAGH1YS/WOSHMvWrK10VKssM/NIpyuiHywR15PhHU5o5n4QrzuU6 /rpW1AkTV5VMiOync0RKVZEpCRs2k4e9Vjd7dSCzSejvd3KwOea9Zpc2oLXqHCfxJxJP G72q6aw0a4nVLfZoF4C8frHrRQyYg4UxxpVeCDOKesTWB2vYuG4J0ULT22J5msyrCx+d uNPAx5fcWwmaD0+aIX6IwHl+JeBbK5EYPaHKn2MYjcQQ5OBNK2darGXgt1wNKDvFt5uJ 3z7dw+lSeI8KLVx9SQML2+4JPwQFYh7I6rMBJcP6FRV1hdNKqBpBJoqgbKx0aPXEC5wp 6mVg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:in-reply-to:mime-version:user-agent:date :message-id:from:cc:references:to:subject:dkim-signature :arc-authentication-results; bh=eOw8ytVspYPA+Q5YFETd/pF/w6MoQVDy8LskEHylZSg=; b=EcR5ayiQogZWLlFyrr6qql+r+P0CLI/zRh0hhoi/K0hwvY/PP8TjImJbHY3RZv1vZk H1bN+s6S2jzfBGpUrRZ9Lrf3vLkbZRlLOBv7ovHJaR63cu5SJcGAXoP+hLgTG8q4wsPy Lu7VeBd7ROR6oR2ofY5DziqVpXO+zGFwMQGnaC5PErvK6193iSnVGmwOOIcJU+rhet/a f4S79tn8GkpOFKfFSGnk2WTBG90uWnzVd23rO6wc00Xx9kr/NuvhmRKo40P/n5NsVVSX a3iZCO14LKqiXpN6DdBINRl7YEJoWnWsZ359+7KOJdC2sUB4ctthM9Y1qrSFtpeH3UQO +ECA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@kapsi.fi header.s=20161220 header.b=xbxPdqg9; spf=pass (google.com: domain of cyndis@kapsi.fi designates 2001:67c:1be8::25 as permitted sender) smtp.mailfrom=cyndis@kapsi.fi Authentication-Results: mx.google.com; dkim=pass header.i=@kapsi.fi header.s=20161220 header.b=xbxPdqg9; spf=pass (google.com: domain of cyndis@kapsi.fi designates 2001:67c:1be8::25 as permitted sender) smtp.mailfrom=cyndis@kapsi.fi Subject: Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer To: Rajkumar Rampelli , robh+dt@kernel.org, mark.rutland@arm.com, thierry.reding@gmail.com, jonathanh@nvidia.com, jdelvare@suse.com, linux@roeck-us.net, corbet@lwn.net, catalin.marinas@arm.com, will.deacon@arm.com, kstewart@linuxfoundation.org, gregkh@linuxfoundation.org, pombredanne@nexb.com, mmaddireddy@nvidia.com, mperttunen@nvidia.com, arnd@arndb.de, gregory.clement@free-electrons.com, timur@codeaurora.org, andy.gross@linaro.org, xuwei5@hisilicon.com, elder@linaro.org, heiko@sntech.de, krzk@kernel.org, ard.biesheuvel@linaro.org References: <1519196339-9377-1-git-send-email-rrajk@nvidia.com> <1519196339-9377-6-git-send-email-rrajk@nvidia.com> Cc: devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pwm@vger.kernel.org, linux-tegra@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, ldewangan@nvidia.com From: Mikko Perttunen Message-ID: Date: Wed, 21 Feb 2018 09:15:10 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <1519196339-9377-6-git-send-email-rrajk@nvidia.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 62.209.167.43 X-SA-Exim-Mail-From: cyndis@kapsi.fi X-SA-Exim-Scanned: No (on mail.kapsi.fi); SAEximRunCond expanded to false X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1592992898629636853?= X-GMAIL-MSGID: =?utf-8?q?1592993873100754129?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: AIUI, the PWM framework already exposes a sysfs node with period information. We should just use that instead of adding a new driver for this. In any case, we cannot add something like this to device tree since it's not a hardware device. Mikko On 21.02.2018 08:58, Rajkumar Rampelli wrote: > Add generic PWM based tachometer driver via HWMON interface > to report the RPM of motor. This drivers get the period/duty > cycle from PWM IP which captures the motor PWM output. > > This driver implements a simple interface for monitoring the speed of > a fan and exposes it in roatations per minute (RPM) to the user space > by using the hwmon's sysfs interface > > Signed-off-by: Rajkumar Rampelli > --- > Documentation/hwmon/generic-pwm-tachometer | 17 +++++ > drivers/hwmon/Kconfig | 10 +++ > drivers/hwmon/Makefile | 1 + > drivers/hwmon/generic-pwm-tachometer.c | 112 +++++++++++++++++++++++++++++ > 4 files changed, 140 insertions(+) > create mode 100644 Documentation/hwmon/generic-pwm-tachometer > create mode 100644 drivers/hwmon/generic-pwm-tachometer.c > > diff --git a/Documentation/hwmon/generic-pwm-tachometer b/Documentation/hwmon/generic-pwm-tachometer > new file mode 100644 > index 0000000..e0713ee > --- /dev/null > +++ b/Documentation/hwmon/generic-pwm-tachometer > @@ -0,0 +1,17 @@ > +Kernel driver generic-pwm-tachometer > +==================================== > + > +This driver enables the use of a PWM module to monitor a fan. It uses the > +generic PWM interface and can be used on SoCs as along as the SoC supports > +Tachometer controller that moniors the Fan speed in periods. > + > +Author: Rajkumar Rampelli > + > +Description > +----------- > + > +The driver implements a simple interface for monitoring the Fan speed using > +PWM module and Tachometer controller. It requests period value through PWM > +capture interface to Tachometer and measures the Rotations per minute using > +received period value. It exposes the Fan speed in RPM to the user space by > +using the hwmon's sysfs interface. > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig > index ef23553..8912dcb 100644 > --- a/drivers/hwmon/Kconfig > +++ b/drivers/hwmon/Kconfig > @@ -1878,6 +1878,16 @@ config SENSORS_XGENE > If you say yes here you get support for the temperature > and power sensors for APM X-Gene SoC. > > +config GENERIC_PWM_TACHOMETER > + tristate "Generic PWM based tachometer driver" > + depends on PWM > + help > + Enables a driver to use PWM signal from motor to use > + for measuring the motor speed. The RPM is captured by > + PWM modules which has PWM capture capability and this > + drivers reads the captured data from PWM IP to convert > + it to speed in RPM. > + > if ACPI > > comment "ACPI drivers" > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile > index f814b4a..9dcc374 100644 > --- a/drivers/hwmon/Makefile > +++ b/drivers/hwmon/Makefile > @@ -175,6 +175,7 @@ obj-$(CONFIG_SENSORS_WM8350) += wm8350-hwmon.o > obj-$(CONFIG_SENSORS_XGENE) += xgene-hwmon.o > > obj-$(CONFIG_PMBUS) += pmbus/ > +obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o > > ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG > > diff --git a/drivers/hwmon/generic-pwm-tachometer.c b/drivers/hwmon/generic-pwm-tachometer.c > new file mode 100644 > index 0000000..9354d43 > --- /dev/null > +++ b/drivers/hwmon/generic-pwm-tachometer.c > @@ -0,0 +1,112 @@ > +/* > + * Copyright (c) 2017-2018, NVIDIA CORPORATION. All rights reserved. > + * > + * This program is free software; you can redistribute it and/or modify it > + * under the terms and conditions of the GNU General Public License, > + * version 2, as published by the Free Software Foundation. > + * > + * This program is distributed in the hope it will be useful, but WITHOUT > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or > + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for > + * more details. > + * > + */ > + > +#include > +#include > +#include > +#include > +#include > +#include > + > +struct pwm_hwmon_tach { > + struct device *dev; > + struct pwm_device *pwm; > + struct device *hwmon; > +}; > + > +static ssize_t show_rpm(struct device *dev, struct device_attribute *attr, > + char *buf) > +{ > + struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev); > + struct pwm_device *pwm = ptt->pwm; > + struct pwm_capture result; > + int err; > + unsigned int rpm = 0; > + > + err = pwm_capture(pwm, &result, 0); > + if (err < 0) { > + dev_err(ptt->dev, "Failed to capture PWM: %d\n", err); > + return err; > + } > + > + if (result.period) > + rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC, > + result.period); > + > + return sprintf(buf, "%u\n", rpm); > +} > + > +static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0); > + > +static struct attribute *pwm_tach_attrs[] = { > + &sensor_dev_attr_rpm.dev_attr.attr, > + NULL, > +}; > + > +ATTRIBUTE_GROUPS(pwm_tach); > + > +static int pwm_tach_probe(struct platform_device *pdev) > +{ > + struct pwm_hwmon_tach *ptt; > + int err; > + > + ptt = devm_kzalloc(&pdev->dev, sizeof(*ptt), GFP_KERNEL); > + if (!ptt) > + return -ENOMEM; > + > + ptt->dev = &pdev->dev; > + > + platform_set_drvdata(pdev, ptt); > + dev_set_drvdata(&pdev->dev, ptt); > + > + ptt->pwm = devm_of_pwm_get(&pdev->dev, pdev->dev.of_node, NULL); > + if (IS_ERR(ptt->pwm)) { > + err = PTR_ERR(ptt->pwm); > + dev_err(&pdev->dev, "Failed to get pwm handle, err: %d\n", > + err); > + return err; > + } > + > + ptt->hwmon = devm_hwmon_device_register_with_groups(&pdev->dev, > + "pwm_tach", ptt, pwm_tach_groups); > + if (IS_ERR(ptt->hwmon)) { > + err = PTR_ERR_OR_ZERO(ptt->hwmon); > + dev_err(&pdev->dev, "Failed to register hwmon device: %d\n", > + err); > + return err; > + } > + > + return 0; > +} > + > +static const struct of_device_id pwm_tach_of_match[] = { > + { .compatible = "generic-pwm-tachometer" }, > + {} > +}; > +MODULE_DEVICE_TABLE(of, pwm_tach_of_match); > + > +static struct platform_driver pwm_tach_driver = { > + .driver = { > + .name = "generic-pwm-tachometer", > + .of_match_table = pwm_tach_of_match, > + }, > + .probe = pwm_tach_probe, > +}; > + > +module_platform_driver(pwm_tach_driver); > + > +MODULE_DESCRIPTION("PWM based Generic Tachometer driver"); > +MODULE_AUTHOR("Laxman Dewangan "); > +MODULE_AUTHOR("Rajkumar Rampelli "); > +MODULE_LICENSE("GPL v2"); >