linux-kernel - Re: [linux-sunxi] [PATCH 10/10] ARM: dts: sun8i: Add SY8106A regulator to Orange Pi PC

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Message-ID: <1501064628.14577.1.camel@megous.com>
Date:   Wed, 26 Jul 2017 12:23:48 +0200
From:   Ondřej Jirman <megous@...ous.com>
To:     icenowy@...c.io, wens@...e.org
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [linux-sunxi] [PATCH 10/10] ARM: dts: sun8i: Add SY8106A
 regulator to Orange Pi PC

Hi,

icenowy@...c.io píše v St 26. 07. 2017 v 15:36 +0800:
> 
> > > > 
> > > > Otherwse
> > > > 
> > > > > +               regulator-max-microvolt = <1400000>;
> > > > > +               regulator-ramp-delay = <200>;
> > > > 
> > > > Is this an actual constraint of the SoC? Or is it a characteristic
> > > > of the regulator? If it is the latter, it belongs in the driver.
> > > > AFAIK the regulator supports varying the ramp delay (slew rate).
> 
> I don't know...
> 
> Maybe I should ask Ondrej?

It is probably neither.

It is used to calculate a delay inserted by the kernel between setting
a new target voltage over I2C and changing the frequency of the CPU.
The actual delay is calculated by the difference between previous and
the new voltage.

I don't remember seeing anything in the datasheet of the regulator.
This is just some low value that works.

It would probably be dependent on the capacitance on the output of the
regulator, actual load (which varies), etc. So it is a board specific
value. One could measure it with an oscilloscope if there's a need to
optimize this.

regards,
  o.

> > > > 
> > > > ChenYu
> > > > 
> > > > > +               regulator-boot-on;
> > > > > +               regulator-always-on;
> > > > > +       };
> > > > > +};
> > > > > +
> > > > >  &r_pio {
> > > > >         leds_r_opc: led_pins@0 {
> > > > >                 pins = "PL10";
> > > > > --
> > > > > 2.13.0
> > > > > 
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