On Thu, Nov 07, 2024 at 01:06:50PM +0530, Krishna Kurapati wrote: > Enabling U1 and U2 power-saving states can lead to stability and > performance issues, particularly for latency-sensitive or high- > throughput applications. These low-power link states are intended > to reduce power consumption by allowing the device to enter partial > low-power modes during idle periods. However, they can sometimes > result in unexpected behavior. 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 low power states. These packet drops are often reflected > as Missed Isochronous transfers as the controller was not able to > send the 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. > > 4. On older targets like SM8150/SM8250/SM8350, there have been > throughput issues seen during tethering use cases. > > To avoid such issues, the USB team at Qualcomm added these quirks > to all targets in the past 4-5 years and extensive testing was done. > Although these are intermittent power states, disabling them didn't > cause any major increase in power numbers. > > Signed-off-by: Krishna Kurapati <quic_kriskura@xxxxxxxxxxx> > --- > If this is fine, the patch would be made into a series, disabling > U1/U2 for all mobile and QCS targets. > > arch/arm64/boot/dts/qcom/sm8150.dtsi | 4 ++++ > arch/arm64/boot/dts/qcom/sm8250.dtsi | 4 ++++ > arch/arm64/boot/dts/qcom/sm8350.dtsi | 4 ++++ > arch/arm64/boot/dts/qcom/sm8450.dtsi | 2 ++ Should the same set of quirks be applied to SAR2130P too? > 4 files changed, 14 insertions(+) > -- With best wishes Dmitry
