linux-kernel - Re: [PATCH v12 4/4] arm64: dts: qcom: sc7280-herobrine: Add lpi pinmux properties for CRD 3.0/3.1

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Date:   Mon, 2 May 2022 19:13:49 +0530
From:   Srinivasa Rao Mandadapu <quic_srivasam@...cinc.com>
To:     Doug Anderson <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
CC:     Andy Gross <agross@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        <quic_rohkumar@...cinc.com>,
        "Srinivas Kandagatla" <srinivas.kandagatla@...aro.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Judy Hsiao <judyhsiao@...omium.org>,
        "Venkata Prasad Potturu" <quic_potturu@...cinc.com>
Subject: Re: [PATCH v12 4/4] arm64: dts: qcom: sc7280-herobrine: Add lpi
 pinmux properties for CRD 3.0/3.1


On 4/29/2022 9:40 PM, Doug Anderson wrote:
Thanks for your time Doug Anderson!!!
> Hi,
>
> On Thu, Apr 28, 2022 at 5:02 PM Matthias Kaehlcke <mka@...omium.org> wrote:
>> On Wed, Apr 27, 2022 at 10:39:43PM +0530, Srinivasa Rao Mandadapu wrote:
>>> Add LPASS LPI pinctrl properties, which are required for Audio
>>> functionality on herobrine based platforms of rev5+
>>> (aka CRD 3.0/3.1) boards.
>>>
>>> Signed-off-by: Srinivasa Rao Mandadapu <quic_srivasam@...cinc.com>
>>> Co-developed-by: Venkata Prasad Potturu <quic_potturu@...cinc.com>
>>> Signed-off-by: Venkata Prasad Potturu <quic_potturu@...cinc.com>
>> I'm not super firm in pinctrl territory, a few maybe silly questions
>> below.
>>
>>>   arch/arm64/boot/dts/qcom/sc7280-herobrine-crd.dts | 84 +++++++++++++++++++++++
>>>   1 file changed, 84 insertions(+)
>>>
>>> diff --git a/arch/arm64/boot/dts/qcom/sc7280-herobrine-crd.dts b/arch/arm64/boot/dts/qcom/sc7280-herobrine-crd.dts
>>> index deaea3a..dfc42df 100644
>>> --- a/arch/arm64/boot/dts/qcom/sc7280-herobrine-crd.dts
>>> +++ b/arch/arm64/boot/dts/qcom/sc7280-herobrine-crd.dts
>>> @@ -111,6 +111,90 @@ ap_ts_pen_1v8: &i2c13 {
>>>    * - If a pin is not hooked up on Qcard, it gets no name.
>>>    */
>>>
>>> +&lpass_dmic01 {
>>> +     clk {
>>> +             drive-strength = <8>;
>>> +     };
> Ugh, I've been distracted and I hadn't realized we were back to the
> two-level syntax. Definitely not my favorite for all the reasons I
> talked about [1]. I guess you took Bjorn's silence to my response to
> mean that you should switch back to this way? :(
>
> Bjorn: can you clarify?
>
> [1] https://lore.kernel.org/r/CAD=FV=VicFiX6QkBksZs1KLwJ5x4eCte6j5RWOBPN+WwiXm2Cw@mail.gmail.com/
Actually Your comment addressed for MI2S pin control nodes, but missed 
here. Will address same here.
>>> +};
>>> +
>>> +&lpass_dmic01_sleep {
>>> +     clk {
>>> +             drive-strength = <2>;
>> Does the drive strength really matter in the sleep state, is the SoC actively
>> driving the pin?
> My understanding is that if a pin is left as an output in sleep state
> that there is a slight benefit to switching it to drive-strength 2.
Okay. Will keep this setting as it is. Please correct me if my 
understanding is wrong.
>
>
>>> +             bias-disable;
>> What should this be in active/default state? If I understand correctly
>> after a transition from 'sleep' to 'default' this setting will remain,
>> since the default config doesn't specify a setting for bias.
> Your understanding matches mine but I haven't tested it and I remember
> sometimes being surprised in this corner of pinmux before. I think
> it's better to put the bias in the default state if it should be that
> way all the time, or have a bias in both the default and sleep state
> if they need to be different.
Okay. Will update accordingly.