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Some high speed devices performance drop drastically on Rockchip platforms when connected with DWC3-xHCI controller. It's because that the DWC3 controller enable high speed park mode by default, it aims to improve performance with pipelining of multiple packet. However, for some devices (such as UVC with bulk transfer VID:04b4, PID:02f9), when an IN request is sent within 900ns of the ACK of the previous packet, these devices NAKs more than 3 times, it could decrease the performance. These slow devices include: 1. idVendor=04b4, idProduct=02f9, Product: IRay UVC 2. idVendor=1921, idProduct=21863, Product: Sandisk 3. idVendor=3744, idProduct=8552, Manufacturer: Flex Drive In order to improve compatibility with high speed devices, this patch disable HS park mode for USB DWC3 controller on all arm64 SoCs. With this patch, we test RK3588 with one slow device (IRay UVC VID:04b4, PID:02f9) and three fast devices (U2 disk VID:058f, PID:6387; U2 disk VID:0781, PID:557c; U3 disk VID:174c, PID:55aa), all of these device have no performance loss. Signed-off-by: William Wu <william.wu@rock-chips.com> Change-Id: I9037143fa2553317ad7ae55abeafad3b106cafcb
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.