| Message ID | 20240204220851.4783-1-wahrenst@gmx.net |
|---|---|
| Headers | show |
| Series | pwm: Add GPIO PWM driver | expand |
On Sun, Feb 4, 2024 at 11:09 PM Stefan Wahren <wahrenst@gmx.net> wrote: > From: Nicola Di Lieto <nicola.dilieto@gmail.com> > > Add bindings for PWM modulated by GPIO. > > Signed-off-by: Nicola Di Lieto <nicola.dilieto@gmail.com> > Co-developed-by: Stefan Wahren <wahrenst@gmx.net> > Signed-off-by: Stefan Wahren <wahrenst@gmx.net> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Yours, Linus Walleij
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.
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. >
Hello, On Sun, Feb 04, 2024 at 11:08:50PM +0100, Stefan Wahren wrote: > + "#pwm-cells": > + const: 3 > + > + gpios: > + description: > + GPIO to be modulated > + maxItems: 1 Given that we have 3 PWM cells (so there is an u32 that specifies the pwm_chip's line number) it would be obvious to allow several GPIOs. But I guess we can extend this easily if and when the need arises. Otherwise I'm happy with this patch. Best regards Uwe