^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) .. SPDX-License-Identifier: GPL-2.0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) ============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4) Early Printk
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5) ============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7) Mini-HOWTO for using the earlyprintk=dbgp boot option with a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8) USB2 Debug port key and a debug cable, on x86 systems.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) You need two computers, the 'USB debug key' special gadget and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) two USB cables, connected like this::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) [host/target] <-------> [USB debug key] <-------> [client/console]
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) Hardware requirements
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) =====================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) a) Host/target system needs to have USB debug port capability.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) You can check this capability by looking at a 'Debug port' bit in
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) the lspci -vvv output::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) # lspci -vvv
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) ...
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) 00:1d.7 USB Controller: Intel Corporation 82801H (ICH8 Family) USB2 EHCI Controller #1 (rev 03) (prog-if 20 [EHCI])
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) Subsystem: Lenovo ThinkPad T61
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) Latency: 0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) Interrupt: pin D routed to IRQ 19
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) Region 0: Memory at fe227000 (32-bit, non-prefetchable) [size=1K]
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) Capabilities: [50] Power Management version 2
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) Flags: PMEClk- DSI- D1- D2- AuxCurrent=375mA PME(D0+,D1-,D2-,D3hot+,D3cold+)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) Status: D0 PME-Enable- DSel=0 DScale=0 PME+
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) Capabilities: [58] Debug port: BAR=1 offset=00a0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) ^^^^^^^^^^^ <==================== [ HERE ]
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) Kernel driver in use: ehci_hcd
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) Kernel modules: ehci-hcd
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) ...
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) .. note::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) If your system does not list a debug port capability then you probably
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) won't be able to use the USB debug key.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) b) You also need a NetChip USB debug cable/key:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) http://www.plxtech.com/products/NET2000/NET20DC/default.asp
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) This is a small blue plastic connector with two USB connections;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50) it draws power from its USB connections.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52) c) You need a second client/console system with a high speed USB 2.0 port.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) d) The NetChip device must be plugged directly into the physical
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55) debug port on the "host/target" system. You cannot use a USB hub in
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) between the physical debug port and the "host/target" system.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58) The EHCI debug controller is bound to a specific physical USB
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) port and the NetChip device will only work as an early printk
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60) device in this port. The EHCI host controllers are electrically
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) wired such that the EHCI debug controller is hooked up to the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62) first physical port and there is no way to change this via software.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63) You can find the physical port through experimentation by trying
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) each physical port on the system and rebooting. Or you can try
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65) and use lsusb or look at the kernel info messages emitted by the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66) usb stack when you plug a usb device into various ports on the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67) "host/target" system.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69) Some hardware vendors do not expose the usb debug port with a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) physical connector and if you find such a device send a complaint
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71) to the hardware vendor, because there is no reason not to wire
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72) this port into one of the physically accessible ports.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74) e) It is also important to note, that many versions of the NetChip
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75) device require the "client/console" system to be plugged into the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76) right hand side of the device (with the product logo facing up and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77) readable left to right). The reason being is that the 5 volt
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78) power supply is taken from only one side of the device and it
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79) must be the side that does not get rebooted.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81) Software requirements
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82) =====================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84) a) On the host/target system:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86) You need to enable the following kernel config option::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88) CONFIG_EARLY_PRINTK_DBGP=y
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90) And you need to add the boot command line: "earlyprintk=dbgp".
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 91)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 92) .. note::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 93) If you are using Grub, append it to the 'kernel' line in
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 94) /etc/grub.conf. If you are using Grub2 on a BIOS firmware system,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 95) append it to the 'linux' line in /boot/grub2/grub.cfg. If you are
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 96) using Grub2 on an EFI firmware system, append it to the 'linux'
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 97) or 'linuxefi' line in /boot/grub2/grub.cfg or
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 98) /boot/efi/EFI/<distro>/grub.cfg.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 99)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100) On systems with more than one EHCI debug controller you must
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101) specify the correct EHCI debug controller number. The ordering
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102) comes from the PCI bus enumeration of the EHCI controllers. The
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103) default with no number argument is "0" or the first EHCI debug
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104) controller. To use the second EHCI debug controller, you would
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105) use the command line: "earlyprintk=dbgp1"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107) .. note::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108) normally earlyprintk console gets turned off once the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109) regular console is alive - use "earlyprintk=dbgp,keep" to keep
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110) this channel open beyond early bootup. This can be useful for
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111) debugging crashes under Xorg, etc.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113) b) On the client/console system:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115) You should enable the following kernel config option::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117) CONFIG_USB_SERIAL_DEBUG=y
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119) On the next bootup with the modified kernel you should
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120) get a /dev/ttyUSBx device(s).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 122) Now this channel of kernel messages is ready to be used: start
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 123) your favorite terminal emulator (minicom, etc.) and set
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 124) it up to use /dev/ttyUSB0 - or use a raw 'cat /dev/ttyUSBx' to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 125) see the raw output.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 126)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 127) c) On Nvidia Southbridge based systems: the kernel will try to probe
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 128) and find out which port has a debug device connected.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 129)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 130) Testing
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 131) =======
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 132)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 133) You can test the output by using earlyprintk=dbgp,keep and provoking
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 134) kernel messages on the host/target system. You can provoke a harmless
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 135) kernel message by for example doing::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 136)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 137) echo h > /proc/sysrq-trigger
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 138)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 139) On the host/target system you should see this help line in "dmesg" output::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 140)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 141) SysRq : HELP : loglevel(0-9) reBoot Crashdump terminate-all-tasks(E) memory-full-oom-kill(F) kill-all-tasks(I) saK show-backtrace-all-active-cpus(L) show-memory-usage(M) nice-all-RT-tasks(N) powerOff show-registers(P) show-all-timers(Q) unRaw Sync show-task-states(T) Unmount show-blocked-tasks(W) dump-ftrace-buffer(Z)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 142)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 143) On the client/console system do::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 144)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 145) cat /dev/ttyUSB0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 146)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 147) And you should see the help line above displayed shortly after you've
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 148) provoked it on the host system.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 149)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 150) If it does not work then please ask about it on the linux-kernel@vger.kernel.org
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 151) mailing list or contact the x86 maintainers.
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
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