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

[Linus Walleij]

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