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

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Date:   Thu, 26 Oct 2023 22:03:43 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Stephan Gerhold <stephan@...hold.net>
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 10/26/23 21:17, Stephan Gerhold wrote:
> 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.
Hmm okay I see..

Generally it's rather "no bueno" to have two DT nodes consuming the
same register space.. What happens when you enable BMS on a device
with a non-PM8916 charger? Does it correctly recognize "no battery"
etc.?

Konrad