Re: [PATCH 1/2] iio: ltc2983: add support for optional reset gpio

["Nuno Sá" <noname.nuno@gmail.com>]

On Mon, 2021-08-23 at 17:27 +0300, Andy Shevchenko wrote:
> On Mon, Aug 23, 2021 at 3:51 PM Nuno Sá <noname.nuno@gmail.com>
> wrote:
> > On Mon, 2021-08-23 at 14:14 +0300, Andy Shevchenko wrote:
> > > On Fri, Aug 20, 2021 at 9:53 AM Nuno Sá <nuno.sa@analog.com>
> > > wrote:
> > > > Check if an optional reset gpio is present and if so, make sure
> > > > to
> > > > reset
> > > > the device.
> > > 
> > > ...
> > > 
> > > > +               usleep_range(1000, 1005);
> > > 
> > > The delta should be at least 20%, otherwise I'm not sure why such
> > > a
> > > strict range?
> > > 
> > 
> > No special reason... I just had no hard requirement for delta so I
> > just
> > gave something small. Is 20% documented anywhere?
> 
> Quick search shows nothing, but I remember I saw it somewhere.
> So, the explanation is empirical, because the idea behind is to allow
> less HRT interrupts. When you do a tough margin, you may generate too
> many interrupts from the timer. So, 20% seems like a good balance for
> most of the values.
> 

I see, that makes sense to me.

> The parameters to take into account are:
>  - minimum (or maybe rather median?) CPU frequency the code will be
> run on
>  - minimal sleep (for small sleeps even better to have udelay() as I
> believe documented in timers.rst, for bigger sleeps, like 10ms the
> margin can be 10% or so)

udelay() would be for sleeps < 10us

- Nuno Sá