linux-kernel - Re: [PATCH v2 3/4] arm64: dts: qcom: qcm2290: add LPASS LPI pin controller

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Message-ID: <56vmqgrjy3je7omzirxnfxtuocebbj356iaew5thgkagi35464@hh34y7efssow>
Date: Tue, 21 Oct 2025 16:03:48 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Alexey Klimov <alexey.klimov@...aro.org>
Cc: Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Srinivas Kandagatla <srini@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-sound@...r.kernel.org
Subject: Re: [PATCH v2 3/4] arm64: dts: qcom: qcm2290: add LPASS LPI pin
 controller

On Tue, Oct 21, 2025 at 01:56:09PM +0100, Alexey Klimov wrote:
> On Fri Oct 17, 2025 at 11:42 PM BST, Bjorn Andersson wrote:
> > On Fri, Oct 10, 2025 at 01:29:38PM +0100, Alexey Klimov wrote:
> >> On Tue Oct 7, 2025 at 1:39 PM BST, Konrad Dybcio wrote:
> >> > On 10/7/25 4:03 AM, Alexey Klimov wrote:
> >> >> Add the Low Power Audio SubSystem Low Power Island (LPASS LPI) pin
> >> >> controller device node required for audio subsystem on Qualcomm
> >> >> QRB2210 RB1. QRB2210 is based on qcm2290 which is based on sm6115.
> >> >> 
> >> >> While at this, also add description of lpi_i2s2 pins (active state)
> >> >> required for audio playback via HDMI/I2S.
> >> >> 
> >> >> Cc: Srinivas Kandagatla <srini@...nel.org>
> >> >> Signed-off-by: Alexey Klimov <alexey.klimov@...aro.org>
> >> >> ---
> >> >
> >> > [...]
> >> >
> >> >> +			lpi_i2s2_active: lpi-i2s2-active-state {
> >> >> +				data-pins {
> >> >> +					pins = "gpio12";
> >> >> +					function = "i2s2_data";
> >> >> +					bias-disable;
> >> >> +					drive-strength = <8>;
> >> >> +					output-high;
> >> >
> >> > I.. doubt output-high is what you want?
> >> 
> >> Why? Or is it because of some in-kernel gpiod?
> >> 
> >
> > What does "output-high" mean for a non-gpio function?
> 
> This is not efficient. It will be more useful to go straight to
> the point.

It is efficient. It makes everybody think about it (and ask the same
question in future) instead of just depending on maintainers words.

> This description of pins was taken from Qualcomm downstream code
> and the similar patch was applied (see provided URL in the prev email).

And we all know that downstream can be buggy, incomplete, etc.

> Back to your question -- does it matter here if it is gpio or non-gpio
> function?

It does. The I2S data pin is supposed to be toggled in some way by a
certain IP core. What would it mean if we program output-high? Will the
pin still be toggled (by the function) or stay pulled up (because of the
output being programmed)?

-- 
With best wishes
Dmitry