Re: [PATCH v2 2/2] dt-bindings: iio: dac: Add docs for AD5758 DAC

From: Jonathan Cameron
Date: Sat Jun 16 2018 - 13:49:59 EST


On Mon, 11 Jun 2018 10:42:35 +0200
Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:

> On Thu, Jun 7, 2018 at 3:11 PM, Stefan Popa <stefan.popa@xxxxxxxxxx> 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