Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer

Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer

[Rob Herring]

On Wed, Feb 21, 2018 at 05:20:29PM +0200, Mikko Perttunen wrote:
> On 21.02.2018 16:46, Guenter Roeck wrote:
> > On 02/20/2018 11:15 PM, Mikko Perttunen wrote:
> > > AIUI, the PWM framework already exposes a sysfs node with period
> > > information. We should just use that instead of adding a new driver
> > > for this.
> > > 
> > 
> > I am kind of lost. Please explain.
> > 
> > Are you saying that we should drop the pwm-fan driver as well (which goes
> > the opposite way), as well as any other drivers doing anything with pwm
> > signals,
> > because after all those signals are already exposed to userspace a sysfs
> > attributes,
> > and a kernel driver to abstract those values is thus not needed ?
> 
> The only thing this driver does is do a constant division in kernelspace.
> I'm not really seeing why that couldn't be done in userspace. But if you
> think it's appropriate to do the RPM conversion in kernelspace then I'm not
> greatly opposed to that.
> 
> > 
> > > In any case, we cannot add something like this to device tree since
> > > it's not a hardware device.
> > > 
> > 
> > So you are saying there is no means to express in devicetree that
> > a pwm input is connected to a fan ? How is that not hardware ?
> > 
> > If so, how do you express in devicetree that a pwm signal is connected
> > to anything ?
> 
> If we want to describe that the tachometer is connected to a fan, then we
> should have a fan node in the board's device tree. We don't have a chip that
> has a thing called "generic-pwm-tachometer" attached to it. (We have chips
> that have a "nvidia,tegra186-tachometer", so it's proper to have that.)

We already have some fan control bindings in the tree. Follow those. 
There's only so many ways to control fans, so lets have some alignment. 
And yes, we should have a fan node. 

Rob
--
To unsubscribe from this list: send the line "unsubscribe linux-doc" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer

[Rajkumar Rampelli]

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
>>
>

--
To unsubscribe from this list: send the line "unsubscribe linux-doc" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer

[Guenter Roeck]

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

>>
>>> 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
>>>
>>
> 
> 

--
To unsubscribe from this list: send the line "unsubscribe linux-doc" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer

[Laxman Dewangan]

On Wednesday 07 March 2018 07:50 PM, Guenter Roeck wrote:
> On 03/07/2018 01:47 AM, Rajkumar Rampelli wrote:
>>
>>>
>>> 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.

The RPM is measured speed via PWM signal capture  which is output from fan.
So should we have the fan[1..n]_output_rpm?


--
To unsubscribe from this list: send the line "unsubscribe linux-doc" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer

[Mikko Perttunen]

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
>>>>
>>>
>>
>>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-doc" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer

[Guenter Roeck]

On 03/07/2018 10:06 PM, Laxman Dewangan wrote:
> 
> 
> On Wednesday 07 March 2018 07:50 PM, Guenter Roeck wrote:
>> On 03/07/2018 01:47 AM, Rajkumar Rampelli wrote:
>>>
>>>>
>>>> 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.
> 
> The RPM is measured speed via PWM signal capture  which is output from fan.
> So should we have the fan[1..n]_output_rpm?
> 

No. I hear you clearly that you for some reason dislike fan[1..n]_input.
While ABIs are not always to our liking, that doesn't mean that we get
to change them at our whim. If that is not acceptable for you, I can't
help you. And you can't change inX_input to inX_voltage either, sorry.

Guenter
--
To unsubscribe from this list: send the line "unsubscribe linux-doc" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer

[Guenter Roeck]

On 03/07/2018 11:57 PM, Mikko Perttunen wrote:
> 
> 
> 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.
> 

Ah, sorry, in this case misunderstanding on my side.

Guenter
--
To unsubscribe from this list: send the line "unsubscribe linux-doc" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer

[Laxman Dewangan]

On Thursday 08 March 2018 08:01 PM, Guenter Roeck wrote:
> On 03/07/2018 10:06 PM, Laxman Dewangan wrote:
>>
>>
>> The RPM is measured speed via PWM signal capture  which is output 
>> from fan.
>> So should we have the fan[1..n]_output_rpm?
>>
>
> No. I hear you clearly that you for some reason dislike fan[1..n]_input.
> While ABIs are not always to our liking, that doesn't mean that we get
> to change them at our whim. If that is not acceptable for you, I can't
> help you. And you can't change inX_input to inX_voltage either, sorry.

My opinion is only to not use "input" as this is not really the input to 
fan.
--
To unsubscribe from this list: send the line "unsubscribe linux-doc" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html