From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mikko Perttunen Subject: Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer Date: Wed, 28 Feb 2018 09:03:48 +0200 Message-ID: <4556a8d2-947d-72c4-2962-3167afb53978@kapsi.fi> References: <1519196339-9377-1-git-send-email-rrajk@nvidia.com> <1519196339-9377-6-git-send-email-rrajk@nvidia.com> <5172edff-fe29-7ed1-f0d2-b0359ea2c24d@roeck-us.net> <2510b525-ec36-b49d-5a62-81f335c0d10d@nvidia.com> <2628eff2-dd33-34f4-a7e1-cfe46ef88a3f@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <2628eff2-dd33-34f4-a7e1-cfe46ef88a3f@nvidia.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Rajkumar Rampelli , Guenter Roeck , 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, 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 List-Id: devicetree@vger.kernel.org On 02/28/2018 08:12 AM, Rajkumar Rampelli wrote: > > On Wednesday 28 February 2018 11:28 AM, Guenter Roeck wrote: >> On 02/27/2018 09:38 PM, Rajkumar Rampelli wrote: >>> >>> On Wednesday 21 February 2018 08:20 PM, Guenter Roeck wrote: >>>> On 02/20/2018 10:58 PM, 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, >>>>> +}; >>>> >>>> "rpm" is not a standard hwmon sysfs attribute. If you don't provide >>>> a single standard hwmon sysfs attribute, having a hwmon driver is >>>> pointless. >>> Guenter Roeck, >>> I will define a new hwmon sysfs attribute node called >>> "hwmon_tachometer_attributes" in hwmon.h like below and update the >>> same in tachometer hwmon driver. Is it fine ? >>> enum hwmon_tachometer_attributes { >> >> Are you kidding me ? >> >> Guenter > Sorry, I just wanted to confirm whether my understanding is correct or > not before implementing it actually. > Or, shall I add this attribute as a part of fan attributes with > "hwmon_fan_rpm" ? or any other way to do it ? I need your inputs in > fixing this. I think he wants the attribute to be named according to the properties in this document: https://www.kernel.org/doc/Documentation/hwmon/sysfs-interface. I guess the attribute would then map to fan1_input, though I'm not sure if that's 100% correct either since this could technically be attached to something other than a fan. But I would think in practice that's not a big concern. Guenter, Please correct me as well if I'm wrong. Thank you, Mikko > > -- > To unsubscribe from this list: send the line "unsubscribe linux-tegra" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at  http://vger.kernel.org/majordomo-info.html