linux-kernel - [PATCH v2 1/1] arm64: dts: qcom: qcs615: Set LDO12A regulator to HPM to avoid boot hang

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Message-Id: <20250717072746.987298-1-quic_ziyuzhan@quicinc.com>
Date: Thu, 17 Jul 2025 15:27:46 +0800
From: Ziyue Zhang <quic_ziyuzhan@...cinc.com>
To: andersson@...nel.org, konradybcio@...nel.org, robh@...nel.org,
        krzk+dt@...nel.org, conor+dt@...nel.org, jingoohan1@...il.com,
        mani@...nel.org, lpieralisi@...nel.org, kwilczynski@...nel.org,
        bhelgaas@...gle.com, johan+linaro@...nel.org, vkoul@...nel.org,
        kishon@...nel.org, neil.armstrong@...aro.org, abel.vesa@...aro.org,
        kw@...ux.com
Cc: linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-phy@...ts.infradead.org, qiang.yu@....qualcomm.com,
        quic_krichai@...cinc.com, quic_vbadigan@...cinc.com,
        Ziyue Zhang <ziyue.zhang@....qualcomm.com>,
        Tingguo Cheng <quic_tingguoc@...cinc.com>
Subject: [PATCH v2 1/1] arm64: dts: qcom: qcs615: Set LDO12A regulator to HPM to avoid boot hang

From: Ziyue Zhang <ziyue.zhang@....qualcomm.com>

On certain platforms (e.g., QCS615), consumers of LDO12A—such as PCIe,
UFS, and eMMC—may draw more than 10mA of current during boot. This can
exceed the regulator's limit in Low Power Mode (LPM), triggering current
limit protection and causing the system to hang.

To address this, there are two possible approaches:
a) Set the regulator's initial mode to High Performance Mode (HPM) in
   the device tree.
b) Keep the default LPM setting and have each consumer driver explicitly
   set its current load.

Since some regulators are shared among multiple consumers, and setting
the current must be coordinated across all of them, we will initially
adopt option a by setting the regulator to HPM. We can later migrate to
option b when the timing is appropriate and all consumer drivers are
ready.

Signed-off-by: Ziyue Zhang <ziyue.zhang@....qualcomm.com>
Signed-off-by: Tingguo Cheng <quic_tingguoc@...cinc.com>
---
This patch follows a suggestion from Bjorn Andersson regarding USB
regulator handling where each consumer is expected to explicitly set its
current load.
Link: https://lore.kernel.org/linux-arm-msm/37fc7aa6-23d2-4636-8e02-4957019121a3@quicinc.com/

changes in v2:
 - Delete all LPM mode config in ldo12a, which may lead to potential
   risks
 - Link to v1: https://lore.kernel.org/all/20250716030601.1705364-1-ziyue.zhang@oss.qualcomm.com/
---
 arch/arm64/boot/dts/qcom/qcs615-ride.dts | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/arch/arm64/boot/dts/qcom/qcs615-ride.dts b/arch/arm64/boot/dts/qcom/qcs615-ride.dts
index a6652e4817d1..75effc790c79 100644
--- a/arch/arm64/boot/dts/qcom/qcs615-ride.dts
+++ b/arch/arm64/boot/dts/qcom/qcs615-ride.dts
@@ -166,10 +166,7 @@ vreg_l12a: ldo12 {
 			regulator-name = "vreg_l12a";
 			regulator-min-microvolt = <1800000>;
 			regulator-max-microvolt = <1890000>;
-			regulator-initial-mode = <RPMH_REGULATOR_MODE_LPM>;
-			regulator-allow-set-load;
-			regulator-allowed-modes = <RPMH_REGULATOR_MODE_LPM
-						   RPMH_REGULATOR_MODE_HPM>;
+			regulator-initial-mode = <RPMH_REGULATOR_MODE_HPM>;
 		};
 
 		vreg_l13a: ldo13 {
-- 
2.34.1