Re: [PATCH V4 0/2] pwm: Add GPIO PWM driver

Re: [PATCH V4 0/2] pwm: Add GPIO PWM driver

[Dhruva Gole]

Hi,

On Feb 04, 2024 at 23:08:49 +0100, Stefan Wahren wrote:
> Add a software PWM which toggles a GPIO from a high-resolution timer.
> 
> Recent discussions in the Raspberry Pi community revealt that a lot
> of users still use MMIO userspace tools for GPIO access. One argument
> for this approach is the lack of a GPIO PWM kernel driver. So this
> series tries to fill this gap.
> 
> This continues the work of Vincent Whitchurch [1], which is easier
> to read and more consequent by rejecting sleeping GPIOs than Nicola's
> approach [2].
> 
> The work has been tested on a Raspberry Pi 3 B+ and a cheap logic
> analyzer.

I recently came across this series and I have to say that it will sure be
a nice to have feature to be able to use any GPIO as a PWM.

However, just a minor suggestion is that we should make sure it's well
documented how to actually use this. It would be much appreciated if you
could include some basic documentation of a few sysfs commands or any
userspace library that you used to test what you've mentioned above.

Maybe add another patch for this page?
https://docs.kernel.org/driver-api/pwm.html#using-pwms-with-the-sysfs-interface

This will ensure people know about this feature and will actually be
able to use it.

-- 
Best regards,
Dhruva Gole <d-gole@ti.com>

Re: [PATCH V4 0/2] pwm: Add GPIO PWM driver

[Stefan Wahren]

Hi Dhruva,

Am 05.02.24 um 06:55 schrieb Dhruva Gole:
> Hi,
>
> On Feb 04, 2024 at 23:08:49 +0100, Stefan Wahren wrote:
>> Add a software PWM which toggles a GPIO from a high-resolution timer.
>>
>> Recent discussions in the Raspberry Pi community revealt that a lot
>> of users still use MMIO userspace tools for GPIO access. One argument
>> for this approach is the lack of a GPIO PWM kernel driver. So this
>> series tries to fill this gap.
>>
>> This continues the work of Vincent Whitchurch [1], which is easier
>> to read and more consequent by rejecting sleeping GPIOs than Nicola's
>> approach [2].
>>
>> The work has been tested on a Raspberry Pi 3 B+ and a cheap logic
>> analyzer.
> I recently came across this series and I have to say that it will sure be
> a nice to have feature to be able to use any GPIO as a PWM.
>
> However, just a minor suggestion is that we should make sure it's well
> documented how to actually use this. It would be much appreciated if you
> could include some basic documentation of a few sysfs commands or any
> userspace library that you used to test what you've mentioned above.
i used the PWM sysfs for testing and this PWM driver doesn't change
anything on this well known interface.

Sorry, i don't understand what needs to be documented additionally?
>
> Maybe add another patch for this page?
> https://docs.kernel.org/driver-api/pwm.html#using-pwms-with-the-sysfs-interface
>
> This will ensure people know about this feature and will actually be
> able to use it.
>