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

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Date:   Fri, 13 Jan 2023 16:31:13 +0800
From:   Nylon Chen <nylon.chen@...ive.com>
To:     paul.walmsley@...ive.com, palmer@...belt.com,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Cc:     nylon7717@...il.com, zong.li@...ive.com, greentime.hu@...ive.com,
        vincent.chen@...ive.com, Nylon Chen <nylon.chen@...ive.com>
Subject: [PATCH 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-unmatched-schematics-v3.pdf[0].
The behavior of PWM is acitve-high.

According to the descriptionof PWM for pwmcmp in SiFive FU740-C000
Manual[1].
The pwm algorithm is (PW) pulse active time  = (D) duty * (T) period[2].
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.

[0]:https://sifive-china.oss-cn-zhangjiakou.aliyuncs.com/HiFIve%20Unmatched/hifive-unmatched-schematics-v3.pdf
[1]:https://sifive-china.oss-cn-zhangjiakou.aliyuncs.com/HiFIve%20Unmatched/fu740-c000-manual-v1p2.pdf
[2]:https://en.wikipedia.org/wiki/Duty_cycle

Nylon Chen (2):
  riscv: dts: sifive unmatched: Remove PWM controlled LED's active-low
    properties
  pwm: sifive: change the PWM controlled LED algorithm

 arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts | 4 ----
 drivers/pwm/pwm-sifive.c                            | 1 +
 2 files changed, 1 insertion(+), 4 deletions(-)

-- 
2.36.1