linux-kernel - Re: [PATCH v11 0/2] PWM support for HiFive Unleashed

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Date:   Tue, 7 May 2019 16:31:58 +0530
From:   Yash Shah <yash.shah@...ive.com>
To:     Andreas Schwab <schwab@...e.de>
Cc:     Palmer Dabbelt <palmer@...ive.com>, linux-pwm@...r.kernel.org,
        linux-riscv@...ts.infradead.org,
        Thierry Reding <thierry.reding@...il.com>, robh+dt@...nel.org,
        mark.rutland@....com, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Sachin Ghadi <sachin.ghadi@...ive.com>,
        Paul Walmsley <paul.walmsley@...ive.com>
Subject: Re: [PATCH v11 0/2] PWM support for HiFive Unleashed

Hi Andreas,
On Tue, May 7, 2019 at 3:09 PM Andreas Schwab <schwab@...e.de> wrote:
>
> On Mai 02 2019, Yash Shah <yash.shah@...ive.com> wrote:
>
> > The PWM default output state is high (When duty cycle is 0), So I
> > guess leds will remain on by default.
>
> So that's the bug that needs to be fixed.

Sorry I didn't probably get you before. I now understood the scenario.

Leds on HiFive Unleashed are wired to supply instead of ground.
And as per ./Documentation/devicetree/bindings/leds/leds-pwm.txt, you
need to provide additional property "active-low" in such case.

- active-low : (optional) For PWMs where the LED is wired to supply
rather than ground.

The leds will remain off by default when you add the "active-low"
property under the pwm-leds subnode in your DT file. So, this isn't a
bug in the driver code.
For DT file change, you may refer
https://github.com/yashshah7/riscv-linux/commit/dd55057a26150e50525643a423b20e07b72617b5

Can you test this at your end and confirm?

- Yash
>
> Andreas.
>
> --
> Andreas Schwab, SUSE Labs, schwab@...e.de
> GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
> "And now for something completely different."

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