2022-01-24 16:14:30 +00:00
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apu-ehci - route AMD APU USB ports to EHCI instaed of XHCI
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==========================================================
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This repository contains the source code to a small C-language program
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that can be compiled + executed on a Linux system running the AMD APU
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SoC such as those used in the APU2/3/4 boards of PC-Engines.
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The tool will re-configure the USB ports of the APU SoC to route
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USB Ports 8+9 (those exposed on the physical USB-A connectors of the
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PC-Engines boards) from XHCI to EHCI.
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Why would one want to do this? To work around bugs in the XHCI
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controller firmware, such as miscalculation of the available isochronous
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bandwidth for full-speed devices. For OHCI/UHCI/EHCI, the operating
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system (Linux kernel) is responsible for this, and it does tend to get
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it right. With XHCI, this is implemented in proprietary vendor
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firmware, which does tend to get it wrong.
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Homepage
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--------
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The official homepage / repository of the project is
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<https://git.sysmocom.de/sysmocom/apu-ehci>
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GIT Repository
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--------------
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You can clone from the official libosmocore.git repository using
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git clone https:///git.sysmocom.de/apu-ehci
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Building
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--------
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As long as you have a C compiler and make installed, all you need to do
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is to run `make` to build this.
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Running
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-------
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The following command will enable the USB-to-EHCI routing:
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./apu-ehci enable
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2022-01-25 00:35:40 +00:00
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Which should render something like this in your dmesg:
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usb 2-1: USB disconnect, device number 2
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pci 0000:00:16.0: [1022:7808] type 00 class 0x0c0320
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pci 0000:00:16.0: reg 0x10: [mem 0x00000000-0x000000ff]
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pci 0000:00:16.0: supports D1 D2
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pci 0000:00:16.0: PME# supported from D0 D1 D2 D3hot D3cold
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pci 0000:00:16.0: BAR 0: assigned [mem 0xe0000000-0xe00000ff]
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pci 0000:00:16.0: enabling device (0000 -> 0002)
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pci 0000:00:16.0: PME# does not work under D3, disabling it
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ehci-pci 0000:00:16.0: EHCI Host Controller
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ehci-pci 0000:00:16.0: new USB bus registered, assigned bus number 4
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ehci-pci 0000:00:16.0: applying AMD SB700/SB800/Hudson-2/3 EHCI dummy qh workaround
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ehci-pci 0000:00:16.0: debug port 2
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ehci-pci 0000:00:16.0: irq 55, io mem 0xe0000000
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ehci-pci 0000:00:16.0: USB 2.0 started, EHCI 1.00
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usb usb4: New USB device found, idVendor=1d6b, idProduct=0002, bcdDevice= 5.10
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usb usb4: New USB device strings: Mfr=3, Product=2, SerialNumber=1
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usb usb4: Product: EHCI Host Controller
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usb usb4: Manufacturer: Linux 5.10.0-10-amd64 ehci_hcd
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usb usb4: SerialNumber: 0000:00:16.0
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hub 4-0:1.0: USB hub found
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hub 4-0:1.0: 2 ports detected
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usb 4-1: new high-speed USB device number 2 using ehci-pci
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usb 4-1: New USB device found, idVendor=0438, idProduct=7900, bcdDevice= 0.18
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usb 4-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
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hub 4-1:1.0: USB hub found
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hub 4-1:1.0: 2 ports detected
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Furthermore, the USB device[s] attahced to port 8/9 should now re-enumerate on the new bus:
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usb 4-1.1: new full-speed USB device number 3 using ehci-pci
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usb 4-1.1: New USB device found, idVendor=1d50, idProduct=6145, bcdDevice= 0.03
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usb 4-1.1: New USB device strings: Mfr=2, Product=3, SerialNumber=1
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usb 4-1.1: Product: icE1usb
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usb 4-1.1: Manufacturer: osmocom
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usb 4-1.1: SerialNumber: dc697407e7881531
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You can theoretically disable it again with the following command (not working here):
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2022-01-24 16:14:30 +00:00
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./apu-ehci disable
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WARNING:: The tool meddles with low-level internals of the APU SoC, so
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there is a risk it may crash, lock up or otherwise behave strangely. If
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you want to be safe, it is recommended to first unload the `ehci_pci`
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and `xhci_pci` modules before calling the apu-ehci tool. YMMV.
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Further Reading
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---------------
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Official AMD BIOS and Kernel Developer Guide available from
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<https://www.amd.com/system/files/TechDocs/52740_16h_Models_30h-3Fh_BKDG.pdf>
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