Quoting bgodavar@xxxxxxxxxxxxxx (2021-10-12 22:30:50)
> On 2021-10-12 22:54, Stephen Boyd wrote:
> > Quoting Balakrishna Godavarthi (2021-10-12 06:01:38)
> >> diff --git a/arch/arm64/boot/dts/qcom/sc7280-idp.dtsi
> >> b/arch/arm64/boot/dts/qcom/sc7280-idp.dtsi
> >> index 272d5ca..09adc802 100644
> >> --- a/arch/arm64/boot/dts/qcom/sc7280-idp.dtsi
> >> +++ b/arch/arm64/boot/dts/qcom/sc7280-idp.dtsi
> >> + compatible = "qcom,wcn6750-bt";
> >> + pinctrl-names = "default";
> >> + pinctrl-0 = <&bt_en_default>;
> >> + enable-gpios = <&tlmm 85 GPIO_ACTIVE_HIGH>;
> >> + swctrl-gpios = <&tlmm 86 GPIO_ACTIVE_HIGH>;
> >
> > Is there any pinctrl config for gpio 86?
> >
> [Bala]: This is input GPIO to apps, BT SOC will handle configurations.
Ok. So there should be some pinctrl stating that the function is "gpio"
and the biasing is probably bias-disable. The BT SOC will handle setting
any pull, either up or down?
>
> >> + vddaon-supply = <&vreg_s7b_0p9>;
> >> + vddbtcxmx-supply = <&vreg_s7b_0p9>;
> >> + vddrfacmn-supply = <&vreg_s7b_0p9>;
> >> + vddrfa0p8-supply = <&vreg_s7b_0p9>;
> >> + vddrfa1p7-supply = <&vreg_s1b_1p8>;
> >> + vddrfa1p2-supply = <&vreg_s8b_1p2>;
> >> + vddrfa2p2-supply = <&vreg_s1c_2p2>;
> >> + vddasd-supply = <&vreg_l11c_2p8>;
> >> + max-speed = <3200000>;
> >> + };
> >> };
> >>
> >> /* PINCTRL - additions to nodes defined in sc7280.dtsi */
> >> @@ -504,6 +521,14 @@
> >> */
> >> bias-pull-up;
> >> };
> >> +
> >> + bt_en_default: bt_en_default {
> >
> > bt_en: bt-en {
> >
> > Node names shouldn't have underscores and 'default' is redundant.
> >
> [Bala]: will update in next patch.
>
> >> + pins = "gpio85";
> >> + function = "gpio";
> >> + drive-strength = <2>;
> >> + output-low;
> >> + bias-pull-down;
> >
> > Why is there a pull down on an output gpio? Shouldn't this be
> > bias-disable?
> >
>
> [Bala]: BT_EN pin is OP of apps and input to BT SoC.
> by default we want the state of BT_EN to be low. so used pull down
> instead of bias-disable
The pin state will be low because of the 'output-low' property.
> as AFAIK bias-disable may trigger a tristate on BT_EN pin, which may
> trigger BT SoC enable
> if it is not actually triggered.
Is the pin ever "turned around" and made an input? If not then it will
be output and be driving low until the enable-gpios is set to output
active. The pull down is probably wasting power when the pin is being
driven either high or low.
