linux-kernel - Re: [PATCH] arm64: dts: qcom: ipq9574: Fix 'l2' regulator min/max voltages

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Message-ID: <aFvOVebZiP/ZxA+N@hu-varada-blr.qualcomm.com>
Date: Wed, 25 Jun 2025 15:54:21 +0530
From: Varadarajan Narayanan <quic_varada@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
CC: <andersson@...nel.org>, <konradybcio@...nel.org>, <robh@...nel.org>,
        <krzk+dt@...nel.org>, <conor+dt@...nel.org>, <lumag@...nel.org>,
        <linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: dts: qcom: ipq9574: Fix 'l2' regulator min/max
 voltages

On Tue, Jun 24, 2025 at 04:38:59PM +0200, Konrad Dybcio wrote:
> On 6/24/25 8:08 AM, Varadarajan Narayanan wrote:
> > On Mon, Jun 23, 2025 at 01:34:22PM +0200, Konrad Dybcio wrote:
> >> On 6/23/25 1:32 PM, Varadarajan Narayanan wrote:
> >>> The min and max voltages on l2 regulator is 850000uV. This was
> >>> incorrectly set at 1800000uV earlier and that affected the
> >>> stability of the networking subsystem.
> >>>
> >>> Fixes: d5506524d9d9 ("arm64: dts: qcom: ipq9574: Add LDO regulator node")
> >>> Signed-off-by: Varadarajan Narayanan <quic_varada@...cinc.com>
> >>> ---
> >>
> >> Shouldn't there be a consumer for it, instead of it being always-on?
> >
> > The uniphy block is the consumer of this voltage. The PMIC configures it
> > to 850000uV based on OTP settings and s/w doesn't change it as uniphy
> > doesn't do scaling.
>
> Is there a chance something in the networking part can probe before
> the regulator driver, resulting in a momentary undervolting?

No. The PMIC configures it to 850000uV based on OTP at power up itself,
before Linux driver probe.

Thanks
Varada