Re: [PATCH V3 0/2] pwm: Add GPIO PWM driver

[Phil Howard <phil@xxxxxxxxxxxxx>]

On Fri, 2 Feb 2024 at 20:13, Stefan Wahren <wahrenst@xxxxxxx> wrote:
>
> Hi Phil,
>
> Am 02.02.24 um 14:19 schrieb Phil Howard:
> > On Sun, 28 Jan 2024 at 16:37, Stefan Wahren <wahrenst@xxxxxxx> 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.
> > *Thank you* for picking this up. I've been stuck down by covid but am aiming
> > to build and test this on a Pi 5 (with a gpio chip over PCIe) to see if it runs-
> > though I am fully expecting a PIO solution (using the Pi 5s RP1) to handle
> > PWM in this case, and hope to rely upon this gpio-pwm module for previous
> > iterations.
> i hope you are doing well.
>
> There will be small functional changes in V4. Since this series based on
> Linux 6.8 and there is no RPi 5 mainline support, you will need to apply
> it on top of rpi-6.8.y.

I've got as far as applying the patches and building myself a 6.8.y kernel,
just dragging the ol' brain kicking and screaming into dts world again.

>
> Should i wait for your test results (no pressure) before sending V4?

Don't wait on my account- (no really, it's chaos here)- send away!

> >
> >> 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.
> >>
> >> V3:
> >>   - rebase on top of v6.8-pwm-next
> >>   - cherry-pick improvements from Nicola's series
> >>   - try to address Uwe's, Linus' and Andy's comments
> >>   - try to avoid GPIO glitches during probe
> >>   - fix pwm_gpio_remove()
> >>   - some code clean up's and comments
> >>
> >> V2:
> >>   - Rename gpio to gpios in binding
> >>   - Calculate next expiry from expected current expiry rather than "now"
> >>   - Only change configuration after current period ends
> >>   - Implement get_state()
> >>   - Add error message for probe failures
> >>   - Stop PWM before unregister
> >>
> >> [1] - https://lore.kernel.org/all/20200915135445.al75xmjxudj2rgcp@xxxxxxxx/T/
> >> [2] - https://lore.kernel.org/all/20201205214353.xapax46tt5snzd2v@xxxxxxxxxxxxxxxxxxx/
> >>
> >> Nicola Di Lieto (1):
> >>    dt-bindings: pwm: Add pwm-gpio
> >>
> >> Vincent Whitchurch (1):
> >>    pwm: Add GPIO PWM driver
> >>
> >>   .../devicetree/bindings/pwm/pwm-gpio.yaml     |  42 ++++
> >>   drivers/pwm/Kconfig                           |  11 +
> >>   drivers/pwm/Makefile                          |   1 +
> >>   drivers/pwm/pwm-gpio.c                        | 221 ++++++++++++++++++
> >>   4 files changed, 275 insertions(+)
> >>   create mode 100644 Documentation/devicetree/bindings/pwm/pwm-gpio.yaml
> >>   create mode 100644 drivers/pwm/pwm-gpio.c
> >>
> >> --
> >> 2.34.1
> >>
>


-- 
Philip Howard
Technology & Lifestyle Writer
gadgetoid.com

Gadgetoid gadg-et-oid [gaj-it-oid]

                                     -adjective

1. having the characteristics or form of a gadget; resembling a
mechanical contrivance or device.