linux-kernel - [PATCH v2 11/19] arm64: dts: qcom: Disable USB U1/U2 entry for SDX75

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Message-ID: <20241213095237.1409174-12-quic_prashk@quicinc.com>
Date: Fri, 13 Dec 2024 15:22:29 +0530
From: Prashanth K <quic_prashk@...cinc.com>
To: Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio
	<konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski
	<krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Krishna Kurapati
	<krishna.kurapati@....qualcomm.com>
CC: <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <cros-qcom-dts-watchers@...omium.org>,
        Prashanth K <quic_prashk@...cinc.com>
Subject: [PATCH v2 11/19] arm64: dts: qcom: Disable USB U1/U2 entry for SDX75

Disable U1 and U2 power-saving states to improve stability of USB.
These low-power link states, designed to reduce power consumption
during idle periods, can cause issues in latency-sensitive or high
throughput use cases. Over the years, some of the issues seen are
as follows:

1. In device mode of operation, when UVC is active, enabling U1/U2
is sometimes causing packets drops due to delay in entry/exit of
intermittent these low power states. These packet drops are often
reflected as missed isochronous transfers, as the controller wasn't
able to send packet in that microframe interval and hence glitches
are seen on the final transmitted video output.

2. On older targets like SM8150/SM8250/SM8350, there have been
throughput issues seen during tethering use cases.

3. On targets like SDX75, intermittent disconnects were observed
with certain cables due to impedence variations.

Disabling these intermittent power states enhances device stability
without affecting power usage.

Signed-off-by: Prashanth K <quic_prashk@...cinc.com>
---
 arch/arm64/boot/dts/qcom/sdx75.dtsi | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/boot/dts/qcom/sdx75.dtsi b/arch/arm64/boot/dts/qcom/sdx75.dtsi
index 5f7e59ecf1ca..8e444a9d00ed 100644
--- a/arch/arm64/boot/dts/qcom/sdx75.dtsi
+++ b/arch/arm64/boot/dts/qcom/sdx75.dtsi
@@ -1037,6 +1037,8 @@ usb_dwc3: usb@...0000 {
 				iommus = <&apps_smmu 0x80 0x0>;
 				snps,dis_u2_susphy_quirk;
 				snps,dis_enblslpm_quirk;
+				snps,dis-u1-entry-quirk;
+				snps,dis-u2-entry-quirk;
 				phys = <&usb_hsphy>,
 				       <&usb_qmpphy>;
 				phy-names = "usb2-phy",
-- 
2.25.1