arm64: dts: qcom: sdx75: Disable USB U1/U2 entry

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@quicinc.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20241231081115.3149850-12-quic_prashk@quicinc.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

diff --git a/arch/arm64/boot/dts/qcom/sdx75.dtsi b/arch/arm64/boot/dts/qcom/sdx75.dtsi
index 68d7dbe037b6ac49c746171e8dabd416c8813a38..06d956f5cd4e7ae814ba4043f9e3530a0456cce8 100644 (file)
--- a/arch/arm64/boot/dts/qcom/sdx75.dtsi
+++ b/arch/arm64/boot/dts/qcom/sdx75.dtsi
@@ -1037,6 +1037,8 @@
                                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",