From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1519224387; cv=none; d=google.com; s=arc-20160816; b=ZOybE/BQGyzXz9q+D/2o4wjbsFTi9H262lTaz759ug9Z/adEGkgkc6PFuCZjJcH/va CytsTRLPdy1SUFw+JdTwD1NNcCHy24b6NDPmPqONQRRdmUvdneFechlCfEo3Xx4b1wYb 5k/FNwQb5gf44S6+Lh6wtecPF3Xak3x67cLfLQPQkjcEvEUoFti2l8pMHNXnzK93/Dkn oMKH9A8yeb7ekLO80WYmiTSCwUo8x4o5mdZKJeGIFl04zRTATevFdRC6LX7rb0u4mkaP o/SO0mmrUk+Y2et0v+0c2RUoNV+tz4qC/unIpg+5dZ7h4miFhxrdlvOkMmf08dwkBLKR QxzQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:content-language:in-reply-to:mime-version :user-agent:date:message-id:from:references:cc:to:subject:sender :dkim-signature:arc-authentication-results; bh=516qXUmpFD7NhqOxsaiexquJM5eANm+Do06FsXD+dbk=; b=TKbff4vzO8+PM61K18j72Wky+ZWgFnnyVxF3y2XQdrjxsWzH8f3a6dPeHQWwbxnD7O N4OiBatdmPb3hxlCoHff4WvNZ1t6SHl4cyddNzlOLjeVN5+kz3Sow2ENIeHP5RcXF3DR gLxw5zVjHVGe9v5NFjx2xhL7iBR/rH1rkB/yNKsA6j3YBVjUjW8jZKjekGyfxZXtZv9A zY8MHJcTTE7gUXj+xZSyWxPOYOEtWfQ3daz7U89hS02iU69OTZpYfgktykuTa6dMoowk EpgV9sBMHGLafAQEudyKqjsSCMM3zihTt1d6UjMUUsBoLO9iYofKNu0YXK+FyTsiU0Dw wA+g== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=IY/sq7Fc; spf=pass (google.com: domain of groeck7@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=groeck7@gmail.com Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=IY/sq7Fc; spf=pass (google.com: domain of groeck7@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=groeck7@gmail.com X-Google-Smtp-Source: AH8x226GBVck9QBtkP8XvEqdo9lzpdDd84YIDMFaqbVK7QGlUTQgf+nv7q5UWQR0pRTu/4Bu535giw== Sender: Guenter Roeck Subject: Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer To: Mikko Perttunen , Rajkumar Rampelli , robh+dt@kernel.org, mark.rutland@arm.com, thierry.reding@gmail.com, jonathanh@nvidia.com, jdelvare@suse.com, 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 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 References: <1519196339-9377-1-git-send-email-rrajk@nvidia.com> <1519196339-9377-6-git-send-email-rrajk@nvidia.com> From: Guenter Roeck Message-ID: Date: Wed, 21 Feb 2018 06:46:23 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1592992898629636853?= X-GMAIL-MSGID: =?utf-8?q?1593022231786688965?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 02/20/2018 11:15 PM, Mikko Perttunen wrote: > 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. > I am kind of lost. Please explain. Are you saying that we should drop the pwm-fan driver as well (which goes the opposite way), as well as any other drivers doing anything with pwm signals, because after all those signals are already exposed to userspace a sysfs attributes, and a kernel driver to abstract those values is thus not needed ? > In any case, we cannot add something like this to device tree since it's not a hardware device. > So you are saying there is no means to express in devicetree that a pwm input is connected to a fan ? How is that not hardware ? If so, how do you express in devicetree that a pwm signal is connected to anything ? Guenter > 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"); >> >