[PATCH v15 0/5] Change PWM-controlled LED pin active mode and algorithm
Uwe Kleine-König
ukleinek at kernel.org
Thu May 29 04:22:47 PDT 2025
Hello Nylon,
On Thu, May 29, 2025 at 11:53:38AM +0800, Nylon Chen wrote:
> 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.
Applied to
https://git.kernel.org/pub/scm/linux/kernel/git/ukleinek/linux.git pwm/for-nexxt
as 6.17-rc1 material. I pondered if this should go in earlier and/or
should get marked for stable. I'm unsure and willing to consider input
here. The problem I see is that while this is a fix, the change is a
breaking one and you need the dts change and the code change applied
either both or none.
Best regards
Uwe
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