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

[Phil Howard <phil@xxxxxxxxxxxxx>]

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.

>
> 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
>