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

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Hi,

On Wed, Jul 26, 2017 at 12:23:48PM +0200, Ondřej Jirman wrote:
> Hi,
> 
> icenowy@aosc.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.

If this is a reasonable default, then this should be in the
driver. You can't expect anyone to properly calculate a ramp delay and
have access to both a scope and the CPU power lines.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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[PATCH 00/10] A trial to Allwinner H3 DVFS support Icenowy Zheng <icenowy@aosc.io> - 2017-07-23 12:30 +0200
  [PATCH 07/10] cpufreq: dt: Add support for some new Allwinner SoCs Icenowy Zheng <icenowy@aosc.io> - 2017-07-23 12:30 +0200
    Re: [PATCH 07/10] cpufreq: dt: Add support for some new Allwinner  SoCs Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-24 11:00 +0200
      Re: [PATCH 07/10] cpufreq: dt: Add support for some new Allwinner SoCs "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-07-24 14:00 +0200
  [PATCH 04/10] ARM: sunxi: h3/h5: Add r_i2c I2C controller Icenowy Zheng <icenowy@aosc.io> - 2017-07-23 12:30 +0200
    Re: [linux-sunxi] [PATCH 04/10] ARM: sunxi: h3/h5: Add r_i2c I2C controller Chen-Yu Tsai <wens@csie.org> - 2017-07-24 05:20 +0200
  [PATCH 08/10] ARM: sun8i: h3: add operating-points-v2 table for CPU Icenowy Zheng <icenowy@aosc.io> - 2017-07-23 12:30 +0200
  [PATCH 03/10] ARM: sunxi: h3/h5: Add r_i2c pinmux node Icenowy Zheng <icenowy@aosc.io> - 2017-07-23 12:30 +0200
    Re: [linux-sunxi] [PATCH 03/10] ARM: sunxi: h3/h5: Add r_i2c pinmux node Chen-Yu Tsai <wens@csie.org> - 2017-07-24 05:10 +0200
      Re: [linux-sunxi] [PATCH 03/10] ARM: sunxi: h3/h5: Add r_i2c pinmux  node icenowy@aosc.io - 2017-07-24 05:10 +0200
  [PATCH 05/10] clk: sunxi-ng: h3: gate then ungate PLL CPU clk after rate change Icenowy Zheng <icenowy@aosc.io> - 2017-07-23 12:30 +0200
    Re: [PATCH 05/10] clk: sunxi-ng: h3: gate then ungate PLL CPU clk  after rate change Stephen Boyd <sboyd@codeaurora.org> - 2017-07-26 02:40 +0200
    Re: [linux-sunxi] [PATCH 05/10] clk: sunxi-ng: h3: gate then ungate  PLL CPU clk after rate change Chen-Yu Tsai <wens@csie.org> - 2017-07-26 09:20 +0200
  [PATCH 09/10] ARM: sun8i: h2+: add SY8113B regulator used by Orange Pi Zero board Icenowy Zheng <icenowy@aosc.io> - 2017-07-23 12:30 +0200
    Re: [linux-sunxi] [PATCH 09/10] ARM: sun8i: h2+: add SY8113B  regulator used by Orange Pi Zero board Chen-Yu Tsai <wens@csie.org> - 2017-07-24 06:10 +0200
  [PATCH 06/10] clk: sunxi-ng: allow set parent clock (PLL_CPUX) for CPUX clock on H3 Icenowy Zheng <icenowy@aosc.io> - 2017-07-23 12:30 +0200
    Re: [linux-sunxi] [PATCH 06/10] clk: sunxi-ng: allow set parent clock  (PLL_CPUX) for CPUX clock on H3 Chen-Yu Tsai <wens@csie.org> - 2017-07-24 05:20 +0200
    Re: [PATCH 06/10] clk: sunxi-ng: allow set parent clock (PLL_CPUX)  for CPUX clock on H3 Stephen Boyd <sboyd@codeaurora.org> - 2017-07-26 02:40 +0200
  [PATCH 02/10] regulator: add support for SY8106A regulator Icenowy Zheng <icenowy@aosc.io> - 2017-07-23 12:30 +0200
    Re: [linux-sunxi] [PATCH 02/10] regulator: add support for SY8106A regulator Chen-Yu Tsai <wens@csie.org> - 2017-07-24 05:10 +0200
      Re: [linux-sunxi] [PATCH 02/10] regulator: add support for SY8106A  regulator icenowy@aosc.io - 2017-07-24 05:20 +0200
        Re: [linux-sunxi] [PATCH 02/10] regulator: add support for SY8106A  regulator icenowy@aosc.io - 2017-07-24 05:40 +0200
          Re: [linux-sunxi] [PATCH 02/10] regulator: add support for SY8106A regulator Chen-Yu Tsai <wens@csie.org> - 2017-07-24 08:20 +0200
        Re: [linux-sunxi] [PATCH 02/10] regulator: add support for SY8106A regulator Chen-Yu Tsai <wens@csie.org> - 2017-07-24 05:40 +0200
      Re: [linux-sunxi] [PATCH 02/10] regulator: add support for SY8106A  regulator Mark Brown <broonie@kernel.org> - 2017-07-24 17:10 +0200
  [PATCH 10/10] ARM: dts: sun8i: Add SY8106A regulator to Orange Pi PC Icenowy Zheng <icenowy@aosc.io> - 2017-07-23 12:30 +0200
    Re: [linux-sunxi] [PATCH 10/10] ARM: dts: sun8i: Add SY8106A  regulator to Orange Pi PC Chen-Yu Tsai <wens@csie.org> - 2017-07-26 09:10 +0200
      Re: [linux-sunxi] [PATCH 10/10] ARM: dts: sun8i: Add SY8106A regulator to Orange Pi PC Icenowy Zheng <icenowy@aosc.io> - 2017-07-26 09:20 +0200
        Re: [linux-sunxi] [PATCH 10/10] ARM: dts: sun8i: Add SY8106A  regulator to Orange Pi PC Chen-Yu Tsai <wens@csie.org> - 2017-07-26 09:40 +0200
          Re: [linux-sunxi] [PATCH 10/10] ARM: dts: sun8i: Add SY8106A  regulator to Orange Pi PC icenowy@aosc.io - 2017-07-26 09:40 +0200
            Re: [linux-sunxi] [PATCH 10/10] ARM: dts: sun8i: Add SY8106A  regulator to Orange Pi PC Ondřej Jirman <megous@megous.com> - 2017-07-26 12:40 +0200
              Re: [linux-sunxi] [PATCH 10/10] ARM: dts: sun8i: Add SY8106A  regulator to Orange Pi PC Maxime Ripard <maxime.ripard@free-electrons.com> - 2017-07-26 13:50 +0200
                Re: [linux-sunxi] [PATCH 10/10] ARM: dts: sun8i: Add SY8106A  regulator to Orange Pi PC icenowy@aosc.io - 2017-07-26 14:50 +0200
                Re: [linux-sunxi] [PATCH 10/10] ARM: dts: sun8i: Add SY8106A  regulator to Orange Pi PC Ondřej Jirman <megous@megous.com> - 2017-07-26 15:00 +0200
  [PATCH 01/10] dt-bindings: add binding for the SY8160A voltage regulator Icenowy Zheng <icenowy@aosc.io> - 2017-07-23 12:30 +0200
    Re: [linux-sunxi] [PATCH 01/10] dt-bindings: add binding for the  SY8160A voltage regulator Chen-Yu Tsai <wens@csie.org> - 2017-07-24 05:10 +0200

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