linux-kernel - [PATCH v10 0/3] Change PWM-controlled LED pin active mode and algorithm

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Message-Id: <20241224093902.1632627-1-nylon.chen@sifive.com>
Date: Tue, 24 Dec 2024 17:38:58 +0800
From: Nylon Chen <nylon.chen@...ive.com>
To: linux-kernel@...r.kernel.org,
	linux-pwm@...r.kernel.org,
	devicetree@...r.kernel.org
Cc: Nylon Chen <nylon.chen@...ive.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Samuel Holland <samuel.holland@...ive.com>,
	linux-riscv@...ts.infradead.org
Subject: [PATCH v10 0/3] Change PWM-controlled LED pin active mode and algorithm

According to the circuit diagram of User LEDs - RGB described in the
manual hifive-unleashed-a00.pdf[0] and hifive-unmatched-schematics-v3.pdf[1].

The behavior of PWM is acitve-high.

According to the descriptionof PWM for pwmcmp in SiFive FU740-C000 Manual[2].

The pwm algorithm is (PW) pulse active time  = (D) duty * (T) period.
The `frac` variable is pulse "inactive" time so we need to invert it.

So this patchset removes active-low in DTS and adds reverse logic to the driver.

Updated patches: 1
New patches: 0
Unchanged patches: 2

Links:
- [0]: https://sifive.cdn.prismic.io/sifive/c52a8e32-05ce-4aaf-95c8-7bf8453f8698_hifive-unleashed-a00-schematics-1.pdf
- [1]: https://sifive.cdn.prismic.io/sifive/6a06d6c0-6e66-49b5-8e9e-e68ce76f4192_hifive-unmatched-schematics-v3.pdf
- [2]: https://sifive.cdn.prismic.io/sifive/1a82e600-1f93-4f41-b2d8-86ed8b16acba_fu740-c000-manual-v1p6.pdf

Changed in v10:
 - Add 'inactive' variable in apply() to match pwm_sifive_get_state() style
 - Update comment about hardware limitation - it cannot generate 0% duty
   cycle rather than 100% duty cycle

Changed in v9:
 - Fix commit message to adhere to 75 columns rule.
 - Update commit message's subject.
 - Add a variable for inactive logic.

Changed in v8:
 - Fix Signed-off-by and Co-developed-by typo.

Changed in v7:
 - Remove active-low strings from hifive-unleashed-a00.dts file.

Changed in v6:
 - Separate the idempotent test bug fixes into a new patch.
 - Move the reversing the duty before the line checking
   state->enabled.
 - Fix the algorithm and change it to take the minimum value first and
   then reverse it.

Changed in v5:
 - Add the updates to the PWM algorithm based on version 2 back in.
 - Replace div64_ul with DIV_ROUND_UP_ULL to correct the error in the
   period value of the idempotent test in pwm_apply_state_debug.

Changed in v4:
 - Remove previous updates to the PWM algorithm.

Changed in v3:
 - Convert the reference link to standard link.
 - Move the inverted function before taking the minimum value.
 - Change polarity check condition(high and low).
 - Pick the biggest period length possible that is not bigger than the
   requested period.

Changed in v2:
 - Convert the reference link to standard link.
 - Fix typo: s/sifive unmatched:/sifive: unmatched:/.
 - Remove active-low from hifive-unleashed-a00.dts.
 - Include this reference link in the dts and pwm commit messages.

Nylon Chen (2):
  pwm: sifive: change the PWM algorithm
  pwm: sifive: Fix the error in the idempotent test within the
    pwm_apply_state_debug function

NylonChen (1):
  riscv: dts: sifive: unleashed/unmatched: Remove PWM controlled LED's
    active-low properties

 .../boot/dts/sifive/hifive-unleashed-a00.dts   | 12 ++++--------
 .../boot/dts/sifive/hifive-unmatched-a00.dts   | 12 ++++--------
 drivers/pwm/pwm-sifive.c                       | 18 ++++++++++--------
 3 files changed, 18 insertions(+), 24 deletions(-)

-- 
2.34.1