Documentation: x86: convert earlyprintk.txt to reST
This converts the plain text documentation to reStructuredText format and add it to Sphinx TOC tree. No essential content change. Signed-off-by: Changbin Du <changbin.du@gmail.com> Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>hifive-unleashed-5.2
Changbin Du
Jonathan Corbet
parent
c2dea5cda0
commit
4b13576002
|
|
@ -1,52 +1,58 @@
|
|||
.. SPDX-License-Identifier: GPL-2.0
|
||||
|
||||
============
|
||||
Early Printk
|
||||
============
|
||||
|
||||
Mini-HOWTO for using the earlyprintk=dbgp boot option with a
|
||||
USB2 Debug port key and a debug cable, on x86 systems.
|
||||
|
||||
You need two computers, the 'USB debug key' special gadget and
|
||||
and two USB cables, connected like this:
|
||||
and two USB cables, connected like this::
|
||||
|
||||
[host/target] <-------> [USB debug key] <-------> [client/console]
|
||||
|
||||
1. There are a number of specific hardware requirements:
|
||||
Hardware requirements
|
||||
=====================
|
||||
|
||||
a.) Host/target system needs to have USB debug port capability.
|
||||
a) Host/target system needs to have USB debug port capability.
|
||||
|
||||
You can check this capability by looking at a 'Debug port' bit in
|
||||
the lspci -vvv output:
|
||||
You can check this capability by looking at a 'Debug port' bit in
|
||||
the lspci -vvv output::
|
||||
|
||||
# lspci -vvv
|
||||
...
|
||||
00:1d.7 USB Controller: Intel Corporation 82801H (ICH8 Family) USB2 EHCI Controller #1 (rev 03) (prog-if 20 [EHCI])
|
||||
Subsystem: Lenovo ThinkPad T61
|
||||
Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
|
||||
Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
|
||||
Latency: 0
|
||||
Interrupt: pin D routed to IRQ 19
|
||||
Region 0: Memory at fe227000 (32-bit, non-prefetchable) [size=1K]
|
||||
Capabilities: [50] Power Management version 2
|
||||
Flags: PMEClk- DSI- D1- D2- AuxCurrent=375mA PME(D0+,D1-,D2-,D3hot+,D3cold+)
|
||||
Status: D0 PME-Enable- DSel=0 DScale=0 PME+
|
||||
Capabilities: [58] Debug port: BAR=1 offset=00a0
|
||||
# lspci -vvv
|
||||
...
|
||||
00:1d.7 USB Controller: Intel Corporation 82801H (ICH8 Family) USB2 EHCI Controller #1 (rev 03) (prog-if 20 [EHCI])
|
||||
Subsystem: Lenovo ThinkPad T61
|
||||
Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
|
||||
Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
|
||||
Latency: 0
|
||||
Interrupt: pin D routed to IRQ 19
|
||||
Region 0: Memory at fe227000 (32-bit, non-prefetchable) [size=1K]
|
||||
Capabilities: [50] Power Management version 2
|
||||
Flags: PMEClk- DSI- D1- D2- AuxCurrent=375mA PME(D0+,D1-,D2-,D3hot+,D3cold+)
|
||||
Status: D0 PME-Enable- DSel=0 DScale=0 PME+
|
||||
Capabilities: [58] Debug port: BAR=1 offset=00a0
|
||||
^^^^^^^^^^^ <==================== [ HERE ]
|
||||
Kernel driver in use: ehci_hcd
|
||||
Kernel modules: ehci-hcd
|
||||
...
|
||||
Kernel driver in use: ehci_hcd
|
||||
Kernel modules: ehci-hcd
|
||||
...
|
||||
|
||||
( If your system does not list a debug port capability then you probably
|
||||
won't be able to use the USB debug key. )
|
||||
.. note::
|
||||
If your system does not list a debug port capability then you probably
|
||||
won't be able to use the USB debug key.
|
||||
|
||||
b.) You also need a NetChip USB debug cable/key:
|
||||
b) You also need a NetChip USB debug cable/key:
|
||||
|
||||
http://www.plxtech.com/products/NET2000/NET20DC/default.asp
|
||||
|
||||
This is a small blue plastic connector with two USB connections;
|
||||
it draws power from its USB connections.
|
||||
|
||||
c.) You need a second client/console system with a high speed USB 2.0
|
||||
port.
|
||||
c) You need a second client/console system with a high speed USB 2.0 port.
|
||||
|
||||
d.) The NetChip device must be plugged directly into the physical
|
||||
debug port on the "host/target" system. You cannot use a USB hub in
|
||||
d) The NetChip device must be plugged directly into the physical
|
||||
debug port on the "host/target" system. You cannot use a USB hub in
|
||||
between the physical debug port and the "host/target" system.
|
||||
|
||||
The EHCI debug controller is bound to a specific physical USB
|
||||
|
|
@ -65,29 +71,31 @@ and two USB cables, connected like this:
|
|||
to the hardware vendor, because there is no reason not to wire
|
||||
this port into one of the physically accessible ports.
|
||||
|
||||
e.) It is also important to note, that many versions of the NetChip
|
||||
e) It is also important to note, that many versions of the NetChip
|
||||
device require the "client/console" system to be plugged into the
|
||||
right hand side of the device (with the product logo facing up and
|
||||
readable left to right). The reason being is that the 5 volt
|
||||
power supply is taken from only one side of the device and it
|
||||
must be the side that does not get rebooted.
|
||||
|
||||
2. Software requirements:
|
||||
Software requirements
|
||||
=====================
|
||||
|
||||
a.) On the host/target system:
|
||||
a) On the host/target system:
|
||||
|
||||
You need to enable the following kernel config option:
|
||||
You need to enable the following kernel config option::
|
||||
|
||||
CONFIG_EARLY_PRINTK_DBGP=y
|
||||
|
||||
And you need to add the boot command line: "earlyprintk=dbgp".
|
||||
|
||||
(If you are using Grub, append it to the 'kernel' line in
|
||||
/etc/grub.conf. If you are using Grub2 on a BIOS firmware system,
|
||||
append it to the 'linux' line in /boot/grub2/grub.cfg. If you are
|
||||
using Grub2 on an EFI firmware system, append it to the 'linux'
|
||||
or 'linuxefi' line in /boot/grub2/grub.cfg or
|
||||
/boot/efi/EFI/<distro>/grub.cfg.)
|
||||
.. note::
|
||||
If you are using Grub, append it to the 'kernel' line in
|
||||
/etc/grub.conf. If you are using Grub2 on a BIOS firmware system,
|
||||
append it to the 'linux' line in /boot/grub2/grub.cfg. If you are
|
||||
using Grub2 on an EFI firmware system, append it to the 'linux'
|
||||
or 'linuxefi' line in /boot/grub2/grub.cfg or
|
||||
/boot/efi/EFI/<distro>/grub.cfg.
|
||||
|
||||
On systems with more than one EHCI debug controller you must
|
||||
specify the correct EHCI debug controller number. The ordering
|
||||
|
|
@ -96,14 +104,15 @@ and two USB cables, connected like this:
|
|||
controller. To use the second EHCI debug controller, you would
|
||||
use the command line: "earlyprintk=dbgp1"
|
||||
|
||||
NOTE: normally earlyprintk console gets turned off once the
|
||||
regular console is alive - use "earlyprintk=dbgp,keep" to keep
|
||||
this channel open beyond early bootup. This can be useful for
|
||||
debugging crashes under Xorg, etc.
|
||||
.. note::
|
||||
normally earlyprintk console gets turned off once the
|
||||
regular console is alive - use "earlyprintk=dbgp,keep" to keep
|
||||
this channel open beyond early bootup. This can be useful for
|
||||
debugging crashes under Xorg, etc.
|
||||
|
||||
b.) On the client/console system:
|
||||
b) On the client/console system:
|
||||
|
||||
You should enable the following kernel config option:
|
||||
You should enable the following kernel config option::
|
||||
|
||||
CONFIG_USB_SERIAL_DEBUG=y
|
||||
|
||||
|
|
@ -115,27 +124,28 @@ and two USB cables, connected like this:
|
|||
it up to use /dev/ttyUSB0 - or use a raw 'cat /dev/ttyUSBx' to
|
||||
see the raw output.
|
||||
|
||||
c.) On Nvidia Southbridge based systems: the kernel will try to probe
|
||||
c) On Nvidia Southbridge based systems: the kernel will try to probe
|
||||
and find out which port has a debug device connected.
|
||||
|
||||
3. Testing that it works fine:
|
||||
Testing
|
||||
=======
|
||||
|
||||
You can test the output by using earlyprintk=dbgp,keep and provoking
|
||||
kernel messages on the host/target system. You can provoke a harmless
|
||||
kernel message by for example doing:
|
||||
You can test the output by using earlyprintk=dbgp,keep and provoking
|
||||
kernel messages on the host/target system. You can provoke a harmless
|
||||
kernel message by for example doing::
|
||||
|
||||
echo h > /proc/sysrq-trigger
|
||||
|
||||
On the host/target system you should see this help line in "dmesg" output:
|
||||
On the host/target system you should see this help line in "dmesg" output::
|
||||
|
||||
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)
|
||||
|
||||
On the client/console system do:
|
||||
On the client/console system do::
|
||||
|
||||
cat /dev/ttyUSB0
|
||||
|
||||
And you should see the help line above displayed shortly after you've
|
||||
provoked it on the host system.
|
||||
And you should see the help line above displayed shortly after you've
|
||||
provoked it on the host system.
|
||||
|
||||
If it does not work then please ask about it on the linux-kernel@vger.kernel.org
|
||||
mailing list or contact the x86 maintainers.
|
||||
|
|
@ -13,3 +13,4 @@ x86-specific Documentation
|
|||
exception-tables
|
||||
kernel-stacks
|
||||
entry_64
|
||||
earlyprintk
|
||||
|
|
|
|||
Loading…
Reference in New Issue