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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@quicinc.com> Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com> Link: https://lore.kernel.org/r/20241231081115.3149850-17-quic_prashk@quicinc.com Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.