linux-kernel - [PATCH v3 0/2] Change PWM-controlled LED pin active mode and algorithm

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Message-Id: <20230420093457.18936-1-nylon.chen@sifive.com>
Date:   Thu, 20 Apr 2023 17:34:55 +0800
From:   Nylon Chen <nylon.chen@...ive.com>
To:     aou@...s.berkeley.edu, conor@...nel.org,
        emil.renner.berthing@...onical.com, geert+renesas@...der.be,
        heiko@...ech.de, krzysztof.kozlowski+dt@...aro.org,
        palmer@...belt.com, paul.walmsley@...ive.com, robh+dt@...nel.org,
        thierry.reding@...il.com, u.kleine-koenig@...gutronix.de,
        devicetree@...r.kernel.org, linux-pwm@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     nylon.chen@...ive.com, nylon7717@...il.com, zong.li@...ive.com,
        greentime.hu@...ive.com, vincent.chen@...ive.com
Subject: [PATCH v3 0/2] 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: 2
New patches: (none)
Unchanged patches: 1

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 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):
  riscv: dts: sifive: unleashed/unmatched: Remove PWM controlled LED's
    active-low properties
  pwm: sifive: change the PWM controlled LED algorithm

 arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts | 4 ----
 arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts | 4 ----
 drivers/pwm/pwm-sifive.c                            | 9 ++++++---
 3 files changed, 6 insertions(+), 11 deletions(-)

-- 
2.40.0