Messages in this thread | | | Subject | Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer | From | Mikko Perttunen <> | Date | Wed, 28 Feb 2018 09:03:48 +0200 |
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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 <rrajk@nvidia.com> >>>>> --- >>>>> 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 <rrajk@nvidia.com> >>>>> + >>>>> +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 <linux/module.h> >>>>> +#include <linux/platform_device.h> >>>>> +#include <linux/err.h> >>>>> +#include <linux/pwm.h> >>>>> +#include <linux/hwmon.h> >>>>> +#include <linux/hwmon-sysfs.h> >>>>> + >>>>> +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
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