linux-kernel - Re: [PATCH 2/2] arm64: dts: qcom: Fully describe fingerprint node on Herobrine

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Date:   Thu, 17 Mar 2022 18:11:09 -0400
From:   Stephen Boyd <swboyd@...omium.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>,
        Alexandru M Stan <amstan@...omium.org>
Subject: Re: [PATCH 2/2] arm64: dts: qcom: Fully describe fingerprint node on Herobrine

Quoting Matthias Kaehlcke (2022-03-17 15:06:38)
> On Wed, Mar 16, 2022 at 06:06:40PM -0700, Stephen Boyd wrote:
> > Update the fingerprint node on Herobrine to match the fingerprint DT
> > binding. This will allow us to drive the reset and boot gpios from the
> > driver when it is re-attached after flashing. We'll also be able to boot
> > the fingerprint processor if the BIOS isn't doing it for us.
> >
> > Cc: Douglas Anderson <dianders@...omium.org>
> > Cc: Matthias Kaehlcke <mka@...omium.org>
> > Cc: Alexandru M Stan <amstan@...omium.org>
> > Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> > ---
> >
> > Depends on https://lore.kernel.org/r/20220317005814.2496302-1-swboyd@chromium.org
> >
> >  arch/arm64/boot/dts/qcom/sc7280-herobrine.dtsi | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/boot/dts/qcom/sc7280-herobrine.dtsi b/arch/arm64/boot/dts/qcom/sc7280-herobrine.dtsi
> > index 984a7faf0888..282dda78ba3f 100644
> > --- a/arch/arm64/boot/dts/qcom/sc7280-herobrine.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/sc7280-herobrine.dtsi
> > @@ -396,13 +396,16 @@ ap_spi_fp: &spi9 {
> >       cs-gpios = <&tlmm 39 GPIO_ACTIVE_LOW>;
> >
> >       cros_ec_fp: ec@0 {
> > -             compatible = "google,cros-ec-spi";
> > +             compatible = "google,cros-ec-fp";
> >               reg = <0>;
> >               interrupt-parent = <&tlmm>;
> >               interrupts = <61 IRQ_TYPE_LEVEL_LOW>;
> >               pinctrl-names = "default";
> >               pinctrl-0 = <&fp_to_ap_irq_l>, <&fp_rst_l>, <&fpmcu_boot0>;
> > +             boot0-gpios = <&tlmm 68 GPIO_ACTIVE_HIGH>;
> > +             reset-gpios = <&tlmm 78 GPIO_ACTIVE_LOW>;
> >               spi-max-frequency = <3000000>;
> > +             vdd-supply = <&pp3300_fp_mcu>;
>
> IIUC userspace controls this regulator. Do you add it just for completeness
> even though the kernel doesn't use it?
>

Yes. Maybe in the future the kernel can use it by keeping the driver
bound and manually controlling the power supply during flashing. In
theory we could then power it down during suspend or when it isn't in
use too as long as we can hide the multi-second power up time.