Messages in this thread | | | Subject | Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer | From | Rajkumar Rampelli <> | Date | Wed, 7 Mar 2018 15:17:51 +0530 |
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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. > >> 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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