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. V4: - address DT bindings comments from Conor Dooley - drop unnecessary MODULE_ALIAS() as suggested by Krzysztof Kozlowski - add range checks to apply which consider the hrtimer resolution (idea comes from Sean Young) - mark driver as atomic as suggested by Sean Young 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 | 228 ++++++++++++++++++ 4 files changed, 282 insertions(+) create mode 100644 Documentation/devicetree/bindings/pwm/pwm-gpio.yaml create mode 100644 drivers/pwm/pwm-gpio.c -- 2.34.1
