linux-kernel - [PATCH 0/2 v2] pwm: add support for duty

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Message-ID: <20240409174126.1296318-1-tgamblin@baylibre.com>
Date: Tue,  9 Apr 2024 13:41:24 -0400
From: Trevor Gamblin <tgamblin@...libre.com>
To: linux-pwm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	u.kleine-koenig@...gutronix.de,
	michael.hennerich@...log.com,
	nuno.sa@...log.com,
	tgamblin@...libre.com,
	dlechner@...libre.com
Subject: [PATCH 0/2 v2] pwm: add support for duty_offset

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. The libpwm [1] tool was also used for testing the
char device functionality.

Note that in addition to the other patches in this series, the changes
to the axi-pwmgen driver rely on [2] and [3], which haven't been picked
up yet.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/ukleinek/libpwm.git/
[2] https://lore.kernel.org/linux-pwm/20240301173343.1086332-1-tgamblin@baylibre.com/
[3] https://lore.kernel.org/linux-pwm/20240314204722.1291993-1-tgamblin@baylibre.com/

---
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@baylibre.com/

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

 drivers/pwm/core.c           | 82 +++++++++++++++++++++++++++++++++---
 drivers/pwm/pwm-axi-pwmgen.c | 34 +++++++++++----
 include/linux/pwm.h          | 15 +++++++
 include/trace/events/pwm.h   |  6 ++-
 4 files changed, 121 insertions(+), 16 deletions(-)

-- 
2.44.0