linux-kernel - Re: [PATCH 4/5] arm64: dts: qcom: sm6350: add LPASS LPI pin controller

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Message-ID: <91812db8-9774-468e-8a8b-10699a63310c@oss.qualcomm.com>
Date: Thu, 29 Jan 2026 12:19:06 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Luca Weiss <luca.weiss@...rphone.com>,
        Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Bjorn Andersson <andersson@...nel.org>, Linus Walleij
 <linusw@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        ~postmarketos/upstreaming@...ts.sr.ht, phone-devel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-gpio@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] arm64: dts: qcom: sm6350: add LPASS LPI pin
 controller

On 1/29/26 9:32 AM, Luca Weiss wrote:
> On Wed Jan 28, 2026 at 11:16 PM CET, Dmitry Baryshkov wrote:
>> On Wed, Jan 28, 2026 at 01:26:52PM +0100, Luca Weiss wrote:
>>> Add LPASS LPI pinctrl node required for audio functionality on SM6350.
>>>
>>> Signed-off-by: Luca Weiss <luca.weiss@...rphone.com>
>>> ---
>>>  arch/arm64/boot/dts/qcom/sm6350.dtsi | 66 ++++++++++++++++++++++++++++++++++++
>>>  1 file changed, 66 insertions(+)
>>>
>>> diff --git a/arch/arm64/boot/dts/qcom/sm6350.dtsi b/arch/arm64/boot/dts/qcom/sm6350.dtsi
>>> index 9f9b9f9af0da..b1fb6c812da7 100644
>>> --- a/arch/arm64/boot/dts/qcom/sm6350.dtsi
>>> +++ b/arch/arm64/boot/dts/qcom/sm6350.dtsi
>>> @@ -1448,6 +1448,72 @@ compute-cb@5 {
>>>  			};
>>>  		};
>>>  
>>> +		lpass_tlmm: pinctrl@...0000 {
>>> +			compatible = "qcom,sm6350-lpass-lpi-pinctrl";
>>> +			reg = <0x0 0x033c0000 0x0 0x20000>,
>>> +			      <0x0 0x03550000 0x0 0x10000>;
>>> +			gpio-controller;
>>> +			#gpio-cells = <2>;
>>> +			gpio-ranges = <&lpass_tlmm 0 0 15>;
>>> +
>>> +			clocks = <&q6afecc LPASS_HW_MACRO_VOTE LPASS_CLK_ATTRIBUTE_COUPLE_NO>,
>>> +				 <&q6afecc LPASS_HW_DCODEC_VOTE LPASS_CLK_ATTRIBUTE_COUPLE_NO>;
>>> +			clock-names = "core",
>>> +				      "audio";
>>> +
>>> +			i2s1_active: i2s1-active-state {
>>> +				clk-pins {
>>> +					pins = "gpio6";
>>> +					function = "i2s1_clk";
>>> +					drive-strength = <8>;
>>> +					bias-disable;
>>> +					output-high;
>>
>> This looks suspicious for the clock pin.
>>
>>> +				};
>>> +
>>> +				ws-pins {
>>> +					pins = "gpio7";
>>> +					function = "i2s1_ws";
>>> +					drive-strength = <8>;
>>> +					bias-disable;
>>> +					output-high;
>>
>> The same
>>
>>> +				};
>>> +
>>> +				data-pins {
>>> +					pins = "gpio8", "gpio9";
>>> +					function = "i2s1_data";
>>> +					drive-strength = <8>;
>>> +					bias-disable;
>>> +					output-high;
>>
>> And here.
> 
> I've taken this pinctrl from downstream lagoon-lpi.dtsi. There the
> active config for these pins have "output-high;" set.
> 
> And fwiw this pinctrl works fine at runtime for driving the speaker.

I tried to find an answer.

A doc for this SoC says that i2s clock pins should be at output-low
(2 mA) when muxed to the i2s_xxx function, with no information about
bias settings (perhaps bias-disable), and in sleep they should be the
same (minus the drive strength note, but 2mA is the lowest setting)

I am further confused because the output-enable bit in the cfg
register specifically says "when in GPIO mode"

Konrad