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

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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.

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

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







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