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Jonathan Bell bafa697f05 usb: xhci: default to Intel scheme for calculating U1/U2 timeouts
By default, the System Exit Latency and Maximum Exit Latency are used to
calculate hub port U1 and U2 timeout values. This has the effect of
aggressively power-managing a SuperSpeed link but devices are known to
report unfeasibly short device exit latencies in their descriptors,
which under certain usage conditions can significantly degrade
throughput as the link spends longer retraining than being in a useable
state.

The Intel heuristic approach calculates a reasonably large
endpoint-dependent U1 timeout, and uses a minimum U2 timeout that is
several multiples of typical U2 exit latencies.

Add a module parameter that defaults to using this scheme.

This should have the effect of squelching interop edge-cases where LPM
noticeably degrades performance, and avoid the usual workaround where
userspace manually disables it.

Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>
2025-11-10 11:10:10 +00:00
2025-11-10 11:10:06 +00:00
2025-11-10 11:09:54 +00:00
2025-11-09 15:10:19 -08:00

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 Restructured Text 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.

Build status for rpi-6.1.y: Pi kernel build tests dtoverlaycheck

Build status for rpi-6.6.y: Pi kernel build tests dtoverlaycheck

Build status for rpi-6.12.y: Pi kernel build tests dtoverlaycheck

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