Am Montag, 19. September 2016, 08:15:30 CEST schrieb Doug Anderson: > Hi, > > On Mon, Sep 19, 2016 at 1:44 AM, Andy Yan <andy.yan at rock-chips.com> wrote: > > The current rk3066a based boards(Rayeager, Bqcurie2, Marsboard) use > > pwm modulate vdd_logic voltage, but the pwm is default disabled and > > the pwm pin acts as a gpio before pwm regulator probed, so the pwm > > regulator driver will get a zero dutycycle at probe time, so change > > the initial dutycycle to zero to match pwm_regulator_init_state check. > > > > Signed-off-by: Andy Yan <andy.yan at rock-chips.com> > > > > --- > > > > arch/arm/boot/dts/rk3066a-bqcurie2.dts | 2 +- > > arch/arm/boot/dts/rk3066a-marsboard.dts | 2 +- > > arch/arm/boot/dts/rk3066a-rayeager.dts | 2 +- > > 3 files changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/arch/arm/boot/dts/rk3066a-bqcurie2.dts > > b/arch/arm/boot/dts/rk3066a-bqcurie2.dts index bc674ee..618450d 100644 > > --- a/arch/arm/boot/dts/rk3066a-bqcurie2.dts > > +++ b/arch/arm/boot/dts/rk3066a-bqcurie2.dts > > @@ -61,7 +61,7 @@ > > > > regulator-min-microvolt = <1200000>; > > regulator-max-microvolt = <1200000>; > > regulator-always-on; > > > > - voltage-table = <1000000 100>, > > + voltage-table = <1000000 0>, > > In my opinion this isn't quite the right answer. I think that you > should add a new property describing the voltage in the case that the > pin is an input and you should fill that property in, like: > > voltage-when-input = <1000000>; I'd think this would be more of a pwm issue, not something the pwm-regulator should need to care about. Ideally the pwm driver should be able to return some state information even if disabled? I.e. deriving a duty-cycle value from its pin state similar to what Doug described below (it's either 0% or 100%) But right now I have a hard time understanding how the pwm could return any duty-cycle information for an input gpio to the pwm-regulator, as I assume the pwm-driver has to probe (and thus set pinctrl to the pwm function) before the pwm-regulator is able to get the pwm handle? > Once you have this property you should ideally be able to read whether > the pin is currently configured as an input or as a special function > at bootup. Note that I don't actually know if this is possible with > the current pinctrl API, but it does seem like the ideal way to do it > since it means you'll work even if the BIOS changes (AKA: if the BIOS > leaves the pin as an input you can keep the voltage the same and if > the BIOS leaves the pin as PWM you can keep the voltage the same). > > It's also possible that you could just add a property that says "init > to a certain value at bootup no matter what the BIOS left it as". As > long as that voltage is the maximum (and you'll lower it later) this > ought to be safe and you shouldn't risk temporarily undervolting > things. > > > Note that, if you haven't already done so, you almost certainly want > to make sure your pinctrl species an "init" state in addition to a > "default" state. See <https://patchwork.kernel.org/patch/7454311/>. > > -Doug
