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In many projects, you need to obtain the available bandwidth of the xhci roothub port. Refer to xhci rev1_2 and use the TRB_GET_BW command to obtain it. hardware tested: 03:00.3 USB controller: Advanced Micro Devices, Inc. [AMD] Raven USB 3.1 (prog-if 30 [XHCI]) Subsystem: Huawei Technologies Co., Ltd. Raven USB 3.1 Flags: bus master, fast devsel, latency 0, IRQ 30 Memory at c0300000 (64-bit, non-prefetchable) [size=1M] Capabilities: [48] Vendor Specific Information: Len=08 <?> Capabilities: [50] Power Management version 3 Capabilities: [64] Express Endpoint, MSI 00 Capabilities: [a0] MSI: Enable- Count=1/8 Maskable- 64bit+ Capabilities: [c0] MSI-X: Enable+ Count=8 Masked- Kernel driver in use: xhci_hcd test progress: 1. cd /sys/kernel/debug/usb/xhci/0000:03:00.3/port_bandwidth# ls FS_BW HS_BW SS_BW 2. test fs speed device cat FS_BW port[1] available bw: 90%. port[2] available bw: 90%. port[3] available bw: 90%. port[4] available bw: 90%. port[5] available bw: 0%. port[6] available bw: 0%. port[7] available bw: 0%. port[8] available bw: 0%. plug in fs usb audio ID 0d8c:013c cat FS_BW port[1] available bw: 76%. port[2] available bw: 76%. port[3] available bw: 76%. port[4] available bw: 76%. port[5] available bw: 0%. port[6] available bw: 0%. port[7] available bw: 0%. port[8] available bw: 0%. 3. test hs speed device cat HS_BW port[1] available bw: 79%. port[2] available bw: 79%. port[3] available bw: 79%. port[4] available bw: 79%. port[5] available bw: 0%. port[6] available bw: 0%. port[7] available bw: 0%. port[8] available bw: 0%. plug in hs usb video ID 0408:1040 cat HS_BW port[1] available bw: 39%. port[2] available bw: 39%. port[3] available bw: 39%. port[4] available bw: 39%. port[5] available bw: 0%. port[6] available bw: 0%. port[7] available bw: 0%. port[8] available bw: 0%. 4.cat SS_BW port[1] available bw: 0%. port[2] available bw: 0%. port[3] available bw: 0%. port[4] available bw: 0%. port[5] available bw: 90%. port[6] available bw: 90%. port[7] available bw: 90%. port[8] available bw: 90%. Signed-off-by: Xu Rao <raoxu@uniontech.com> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com> Link: https://lore.kernel.org/r/20250515135621.335595-3-mathias.nyman@linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.