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Date:   Sat, 16 Jun 2018 18:49:07 +0100
From:   Jonathan Cameron <jic23@kernel.org>
To:     Linus Walleij <linus.walleij@linaro.org>
Cc:     Stefan Popa <stefan.popa@analog.com>,
        Michael Hennerich <Michael.Hennerich@analog.com>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Hartmut Knaack <knaack.h@gmx.de>,
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        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Greg KH <gregkh@linuxfoundation.org>,
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        Randy Dunlap <rdunlap@infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 2/2] dt-bindings: iio: dac: Add docs for AD5758 DAC
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On Mon, 11 Jun 2018 10:42:35 +0200
Linus Walleij <linus.walleij@linaro.org> wrote:

> On Thu, Jun 7, 2018 at 3:11 PM, Stefan Popa <stefan.popa@analog.com> wrote:
> 
> > + - adi,slew: Array of slewrate settings should contain 3 fields:
> > +       1: Should be either 0 or 1 in order to enable or disable slewrate.  
> 
> We have a standard binding in pin control for "slew-rate".
> 
> It doesn't have a unit today though.
> 
> > +       2: Slew rate clock:
> > +               Valid values for the slew rate update frequency [Hz]:
> > +               * 240000
> > +               * 200000
> > +               * 150000
> > +               * 128000
> > +               * 64000
> > +               * 32000
> > +               * 16000
> > +               * 8000
> > +               * 4000
> > +               * 2000
> > +               * 1000
> > +               * 512
> > +               * 256
> > +               * 128
> > +               * 64
> > +               * 16
> > +       3: Slew rate step:
> > +               Defines by how much the output value changes at each update.
> > +               Valid values for the step size LSBs:
> > +               * 4
> > +               * 12
> > +               * 64
> > +               * 120
> > +               * 256
> > +               * 500
> > +               * 1820
> > +               * 2048  
> 
> This is pretty idiomatic and just encodes the configuration fields from the
> hardware into the device tree.
> 
> The normal slew rate unit is Volts per microsecond.
> 
> I get the feeling that we could define that simply, and then calculate
> the slew rate clock and step using that to find the best match for
> a certain slew rate.
> 
> Yours,
> Linus Walleij
Agreed. A single value would be nice if possible.

J