Messages in this thread | | | Subject | Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer | From | Mikko Perttunen <> | Date | Thu, 8 Mar 2018 09:57:22 +0200 |
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On 07.03.2018 16:20, Guenter Roeck wrote: > On 03/07/2018 01:47 AM, Rajkumar Rampelli wrote: >> >> >> On Wednesday 28 February 2018 07:59 PM, Guenter Roeck wrote: >>> On 02/27/2018 11:03 PM, Mikko Perttunen wrote: >>>> 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. >>>> >>> You are absolutely correct. >>> >>> While I am not opposed to ABI changes, the merits of those would need >>> to be >>> discussed on the mailing list. But replacing "fan1_input" with "rpm" is >>> not an acceptable ABI change, even if it may measure something that >>> turns >>> but isn't a fan. >>> >>> If this _is_ in fact supposed to be used for something else but fans, we >>> would have to discuss what that might be, and if hwmon is the >>> appropriate >>> subsystem to measure and report it. This does to some degree lead >>> back to >>> my concern of having the "fan" part of this patch series in the pwm >>> core. >>> I am still not sure if that makes sense. >>> >>> Thanks, >>> Guenter >> I am planning to add tachometer support in pwm-fan.c driver >> (drivers/hwmon/) instead of adding new generic-pwm-tachometer.c >> driver. Measuring RPM value will be done in pwm-fan driver itself >> using pwm capture feature and will add new sysfs attributes under this >> driver to report rpm value of fan. > > There is an existing attribute to report the RPM of fans. It is called > fan[1..n]_input. > > "replacing "fan1_input" with "rpm" is not an acceptable ABI change" > > Preemptive NACK. > > Guenter >
I think the idea here (based on personal discussion with Rajkumar) was to add a "new" sysfs attribute the driver exports, but that attribute would be the existing fan[1..n]_input.
Mikko
>>> >>>> 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 >>>> -- >>>> To unsubscribe from this list: send the line "unsubscribe >>>> linux-hwmon" in >>>> the body of a message to majordomo@vger.kernel.org >>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>>> >>> >> >> >
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