linux-kernel - Re: [PATCH v2 06/11] arm64: dts: meson-g12a-x96-max: add regulators

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Date:   Tue, 19 Mar 2019 21:13:02 +0100
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     Neil Armstrong <narmstrong@...libre.com>
Cc:     khilman@...libre.com, linux-amlogic@...ts.infradead.org,
        Guillaume La Roque <glaroque@...libre.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 06/11] arm64: dts: meson-g12a-x96-max: add regulators

Hi Neil,

On Tue, Mar 19, 2019 at 9:29 AM Neil Armstrong <narmstrong@...libre.com> wrote:
>
> On 18/03/2019 21:13, Martin Blumenstingl wrote:
> > Hi Neil,
> >
> > On Mon, Mar 18, 2019 at 11:06 AM Neil Armstrong <narmstrong@...libre.com> wrote:
> >>
> >> From: Guillaume La Roque <glaroque@...libre.com>
> >>
> >> Add system regulators for the X96 Max Set-Top-Box.
> >>
> >> Still missing
> >> * VDD_EE (0.8V - PWM controlled)
> >> * VDD_CPU (PWM controlled)
> >>
> >> Signed-off-by: Guillaume La Roque <glaroque@...libre.com>
> >> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
> >> ---
> >>  .../boot/dts/amlogic/meson-g12a-x96-max.dts   | 67 +++++++++++++++++++
> >>  1 file changed, 67 insertions(+)
> >>
> >> diff --git a/arch/arm64/boot/dts/amlogic/meson-g12a-x96-max.dts b/arch/arm64/boot/dts/amlogic/meson-g12a-x96-max.dts
> >> index 0edbd00b358f..5c37930b09e2 100644
> >> --- a/arch/arm64/boot/dts/amlogic/meson-g12a-x96-max.dts
> >> +++ b/arch/arm64/boot/dts/amlogic/meson-g12a-x96-max.dts
> > [...]
> >> +       vcc_5v: regulator-vcc_5v {
> >> +               compatible = "regulator-fixed";
> >> +               regulator-name = "VCC_5V";
> >> +               regulator-min-microvolt = <5000000>;
> >> +               regulator-max-microvolt = <5000000>;
> >> +               vin-supply = <&dc_in>;
> >> +
> >> +               gpio = <&gpio GPIOH_8 GPIO_OPEN_DRAIN>;
> >> +               enable-active-high;
> > is there any way to test whether this GPIO is the right one?
> > I couldn't find a reference to a GPIOH_8 regulator in
> > buildroot_openlinux_kernel_4.9_fbdev_20180706
>
> The x96 is based on the U212 reference design, and the GPIOH_8 controls the 5V_EN signal,
> but you are right, it's the wrong polarity here, it should be enable-active-low instead.
> (FYI The SEI510 does not use this at all, 5V is always enabled)
>
> The schematics describes :
> VCC5V_EN (GPIOH_8-Hiz OD): 5V_EN
> L: Enable
> Hiz: Disable
thank you for this explanation!

> FYI, the GPIOH_8 is Open-Drain only, this means this pin cannot pull to TTL 1, only to TTL 0
> or set as input. We need to add a way to describe this in the pinctrl driver somehow....
as far as I understand the pinctrl driver changes would result in an
error when the GPIO is used with "active high" (making incompatible
drivers or .dts easier to see). is this correct?

> I will send a fix on v3
>
> I didn't notice because I power the board using a Type-A to Type-A connector,
> and the 5V from the USB port bypasses this regulator...
this is good to know.
I'm also powering some of my boards using a Type-A to Type-A
connector. I'll need to remember this and this whether boards are
still booting with the DC plug


Regards
Martin