linux-kernel - Re: [RFC 1/4] pwm: sifive: Add DT documentation for SiFive PWM Controller.

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Message-ID: <20181016105103.GB8852@ulmo>
Date:   Tue, 16 Oct 2018 12:51:03 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Atish Patra <atish.patra@....com>
Cc:     Wesley Terpstra <wesley@...ive.com>, palmer@...ive.com,
        linux-riscv@...ts.infradead.org, linux-pwm@...r.kernel.org,
        linux-gpio@...r.kernel.org, linus.walleij@...aro.org,
        robh+dt@...nel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, mark.rutland@....com,
        hch@...radead.org
Subject: Re: [RFC 1/4] pwm: sifive: Add DT documentation for SiFive PWM
 Controller.

On Mon, Oct 15, 2018 at 03:45:46PM -0700, Atish Patra wrote:
> On 10/10/18 6:51 AM, Thierry Reding wrote:
> > On Tue, Oct 09, 2018 at 11:51:22AM -0700, Atish Patra wrote:
> > [...]
> > > +- interrupts: one interrupt per PWM channel (currently unused in the driver)
> > 
> > This should probably say what the interrupt is used for. And once you
> > have that, remove the comment about it being unused in the driver. DT
> > is OS agnostic, so "driver" is very unspecific and your claim may
> > actually be false.
> > 
> > Thierry
> > 
> As per my understanding, they are generated by hardware but no usage of pwm
> interrupts as of now.

It might be useful to say when they are generated. Are they generated
once per period? At the beginning or the end of the period? That kind
of thing.

> I am not sure if removing the entire entry is a good idea.
> What would be the best way to represent that information ?
> 
> May be this ?
> 
> +-interrupts: one interrupt per PWM channel. No usage in HiFive Unleashed
> SoC.

Why do you think you need to say that they are unused? If the hardware
generates these interrupts, then they are "used". If no driver currently
has a use for them, that's driver specific and doesn't belong in the DT
bindings.

Thierry

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