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 QCS6490-Rb3Gen2 Vision kit, ADB connection is heavily unstable
when U1/U2 is enabled. Often when link enters U2, there is a re-
enumeration seen and device is unusable for many use cases.
3. On QCS8300/QCS9100, it is observed that when Link enters U2, when
the cable is disconnected and reconnected to host PC in HS, there
is no link status change interrupt seen and the plug-in in HS doesn't
show up a bus reset and enumeration failure happens.
Disabling these intermittent power states enhances device stability
without affecting power usage.
Signed-off-by: Prashanth K <quic_prashk@xxxxxxxxxxx>
---
arch/arm64/boot/dts/qcom/qcs404.dtsi | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/arm64/boot/dts/qcom/qcs404.dtsi b/arch/arm64/boot/dts/qcom/qcs404.dtsi
index 215ba146207a..a77a22e3f234 100644
--- a/arch/arm64/boot/dts/qcom/qcs404.dtsi
+++ b/arch/arm64/boot/dts/qcom/qcs404.dtsi
@@ -694,6 +694,8 @@ usb3_dwc3: usb@7580000 {
snps,has-lpm-erratum;
snps,hird-threshold = /bits/ 8 <0x10>;
snps,usb3_lpm_capable;
+ snps,dis-u1-entry-quirk;
+ snps,dis-u2-entry-quirk;
dr_mode = "otg";
};
};
@@ -731,6 +733,8 @@ usb@78c0000 {
snps,has-lpm-erratum;
snps,hird-threshold = /bits/ 8 <0x10>;
snps,usb3_lpm_capable;
+ snps,dis-u1-entry-quirk;
+ snps,dis-u2-entry-quirk;
dr_mode = "peripheral";
};
};
--
2.25.1
