linux-kernel - Re: [PATCH v2 2/3] arm64: dts: qcom: pm8916: Add BMS and charger

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Message-ID: <ZTq7XGz4Ux8lYQho@gerhold.net>
Date:   Thu, 26 Oct 2023 21:17:48 +0200
From:   Stephan Gerhold <stephan@...hold.net>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>
Cc:     Nikita Travkin <nikita@...n.ru>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, Lee Jones <lee@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        ~postmarketos/upstreaming@...ts.sr.ht
Subject: Re: [PATCH v2 2/3] arm64: dts: qcom: pm8916: Add BMS and charger

On Thu, Oct 26, 2023 at 08:54:00PM +0200, Konrad Dybcio wrote:
> On 10/24/23 11:29, Nikita Travkin wrote:
> > Konrad Dybcio писал(а) 24.10.2023 13:34:
> > > On 10/23/23 08:20, Nikita Travkin wrote:
> > > > pm8916 contains some hardware blocks for battery powered devices:
> > > > 
> > > > - VM-BMS: Battery voltage monitoring block.
> > > > - LBC: Linear battery charger.
> > > > 
> > > > Add them to the pmic dtsi so the devices that make use of those blocks
> > > > can enable them.
> > > > 
> > > > Signed-off-by: Nikita Travkin <nikita@...n.ru>
> > > > ---
> > > >    arch/arm64/boot/dts/qcom/pm8916.dtsi | 48 ++++++++++++++++++++++++++++++++++++
> > > >    1 file changed, 48 insertions(+)
> > > > 
> > > > diff --git a/arch/arm64/boot/dts/qcom/pm8916.dtsi b/arch/arm64/boot/dts/qcom/pm8916.dtsi
> > > > index f4de86787743..4b2e8fb47d2d 100644
> > > > --- a/arch/arm64/boot/dts/qcom/pm8916.dtsi
> > > > +++ b/arch/arm64/boot/dts/qcom/pm8916.dtsi
> > > > @@ -41,6 +41,35 @@ watchdog {
> > > >    			};
> > > >    		};
> > > >    +		pm8916_charger: charger@...0 {
> > > > +			compatible = "qcom,pm8916-lbc";
> > > > +			reg = <0x1000>, <0x1200>, <0x1300>, <0x1600>;
> > > > +			reg-names = "chgr", "bat_if", "usb", "misc";
> > > > +
> > > > +			interrupts = <0x0 0x10 0 IRQ_TYPE_EDGE_BOTH>,
> > > > +				     <0x0 0x10 5 IRQ_TYPE_EDGE_BOTH>,
> > > > +				     <0x0 0x10 6 IRQ_TYPE_EDGE_BOTH>,
> > > > +				     <0x0 0x10 7 IRQ_TYPE_EDGE_BOTH>,
> > > > +				     <0x0 0x12 0 IRQ_TYPE_EDGE_BOTH>,
> > > > +				     <0x0 0x12 1 IRQ_TYPE_EDGE_BOTH>,
> > > > +				     <0x0 0x13 0 IRQ_TYPE_EDGE_BOTH>,
> > > > +				     <0x0 0x13 1 IRQ_TYPE_EDGE_BOTH>,
> > > > +				     <0x0 0x13 2 IRQ_TYPE_EDGE_BOTH>,
> > > > +				     <0x0 0x13 4 IRQ_TYPE_EDGE_BOTH>;
> > > > +			interrupt-names = "vbat_det",
> > > > +					  "fast_chg",
> > > > +					  "chg_fail",
> > > > +					  "chg_done",
> > > > +					  "bat_pres",
> > > > +					  "temp_ok",
> > > > +					  "coarse_det",
> > > > +					  "usb_vbus",
> > > So, both the charger and the USBIN driver use the same irq? :/
> > > 
> > 
> > AFAIU the usbin extcon driver pretty much just tracks the state
> > of the IRQ to report extcon. It happens to assume the same part
> > of the pmic though, yes, which also means there will be no user
> > that would enable both charger and vbus extcon, since charger
> > driver provides this functionality as well.
> So, should USBIN be removed from PM8916 dt since it's essentially
> a part of the charger block?
> 

The "USB_IN" pad of the PM8916 seems to be connected on pretty much all
devices, even if they are using external chargers and the charging
functionality of PM8916 is completely disabled. For those devices, the
&pm8916_usbin device provides a convenient way to detect the USB state,
even without a working charger driver.

While we could modify the PM8916 charger driver and DT node to have some
special mode where charging and battery monitoring is completely
disabled and only the USBIN extcon is provided, I'm not sure if that
would provide a significant advantage compared to just keeping the
simple &pm8916_usbin node with the existing driver.

Thanks,
Stephan