[PATCH 0/2 v3] pwm: add support for duty_offset

[Trevor Gamblin]

This series extends the PWM subsystem to support the duty_offset feature
found on some PWM devices. It includes a patch to enable this feature
for the axi-pwmgen driver, which can also serve as an example of how to
implement it for other devices.

The series was tested on actual hardware using a Zedboard. An
oscilloscope was used to validate that the generated PWM signals matched
the requested ones. 

Note that in addition to the other patches in this series, the changes
to the axi-pwmgen driver rely on [1], which hasn't been picked up yet.

[1] https://lore.kernel.org/linux-pwm/20240424125850.4189116-1-tgamblin@xxxxxxxxxxxx/

---
v3 changes:
* rebased on top of latest pwm/for-next
* removed changes related to cdev to match current pwm tree
* fixed minor whitespace issue caught by checkpatch

Link to v2: https://lore.kernel.org/linux-pwm/20240409174126.1296318-1-tgamblin@xxxxxxxxxxxx/

v2 changes:
* Address feedback for driver in v1:
  * Remove supports_offset flag in pwm_chip struct, and references to it
    in the axi-pwmgen driver patch
  * Drop pwm_config_full patch entirely
  * Don't return EINVAL when state->duty_offset + state->duty_cycle >
    state->period in __pwm_apply(), since this is valid as long as
    neither is greater than state->period on its own
  * Add a check to disallow setting the PWM signal as inverse and a
    nonzero duty_offset at the same time in __pwm_apply(), with a
    comment explaining why

Link to v1 (RFC): https://lore.kernel.org/linux-pwm/20240405003025.739603-1-tgamblin@xxxxxxxxxxxx/

Trevor Gamblin (2):
  pwm: add duty offset support
  pwm: axi-pwmgen: add duty offset support

 drivers/pwm/core.c           | 79 +++++++++++++++++++++++++++++++++---
 drivers/pwm/pwm-axi-pwmgen.c | 20 ++++++++-
 include/linux/pwm.h          | 15 +++++++
 include/trace/events/pwm.h   |  6 ++-
 4 files changed, 112 insertions(+), 8 deletions(-)

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2.45.1