[PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer
Rajkumar Rampelli
rrajk at nvidia.com
Tue Feb 27 22:12:28 PST 2018
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 at 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 at 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.
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