From mboxrd@z Thu Jan 1 00:00:00 1970 From: Changbin Du Subject: [PATCH v4 43/63] Documentation: x86: convert earlyprintk.txt to reST Date: Wed, 24 Apr 2019 00:29:12 +0800 Message-ID: <20190423162932.21428-44-changbin.du@gmail.com> References: <20190423162932.21428-1-changbin.du@gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20190423162932.21428-1-changbin.du@gmail.com> Sender: linux-kernel-owner@vger.kernel.org To: Jonathan Corbet Cc: Bjorn Helgaas , rjw@rjwysocki.net, linux-pci@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, x86@kernel.org, fenghua.yu@intel.com, linuxppc-dev@lists.ozlabs.org, linux-acpi@vger.kernel.org, linux-gpio@vger.kernel.org, mchehab+samsung@kernel.org, Changbin Du List-Id: linux-gpio@vger.kernel.org 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 --- Documentation/x86/earlyprintk.rst | 148 ++++++++++++++++++++++++++++++ Documentation/x86/earlyprintk.txt | 141 ---------------------------- Documentation/x86/index.rst | 1 + 3 files changed, 149 insertions(+), 141 deletions(-) create mode 100644 Documentation/x86/earlyprintk.rst delete mode 100644 Documentation/x86/earlyprintk.txt diff --git a/Documentation/x86/earlyprintk.rst b/Documentation/x86/earlyprintk.rst new file mode 100644 index 000000000000..519402451f9c --- /dev/null +++ b/Documentation/x86/earlyprintk.rst @@ -0,0 +1,148 @@ +.. 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:: + + [host/target] <-------> [USB debug key] <-------> [client/console] + +There are a number of specific hardware requirements +==================================================== + + 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:: + + # 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- SERR- /grub.cfg.) + + On systems with more than one EHCI debug controller you must + specify the correct EHCI debug controller number. The ordering + comes from the PCI bus enumeration of the EHCI controllers. The + default with no number argument is "0" or the first EHCI debug + 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. + + b) On the client/console system: + + You should enable the following kernel config option:: + + CONFIG_USB_SERIAL_DEBUG=y + + On the next bootup with the modified kernel you should + get a /dev/ttyUSBx device(s). + + Now this channel of kernel messages is ready to be used: start + your favorite terminal emulator (minicom, etc.) and set + 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 + and find out which port has a debug device connected. + +Testing that it works fine +========================== + + 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:: + + 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:: + + cat /dev/ttyUSB0 + + 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. diff --git a/Documentation/x86/earlyprintk.txt b/Documentation/x86/earlyprintk.txt deleted file mode 100644 index 46933e06c972..000000000000 --- a/Documentation/x86/earlyprintk.txt +++ /dev/null @@ -1,141 +0,0 @@ - -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: - - [host/target] <-------> [USB debug key] <-------> [client/console] - -1. There are a number of specific hardware requirements: - - 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: - - # 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- SERR- /grub.cfg.) - - On systems with more than one EHCI debug controller you must - specify the correct EHCI debug controller number. The ordering - comes from the PCI bus enumeration of the EHCI controllers. The - default with no number argument is "0" or the first EHCI debug - 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. - - b.) On the client/console system: - - You should enable the following kernel config option: - - CONFIG_USB_SERIAL_DEBUG=y - - On the next bootup with the modified kernel you should - get a /dev/ttyUSBx device(s). - - Now this channel of kernel messages is ready to be used: start - your favorite terminal emulator (minicom, etc.) and set - 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 - and find out which port has a debug device connected. - -3. Testing that it works fine: - - 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: - - 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: - - cat /dev/ttyUSB0 - - 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. diff --git a/Documentation/x86/index.rst b/Documentation/x86/index.rst index 8a666c5abc85..7b8388ebd43d 100644 --- a/Documentation/x86/index.rst +++ b/Documentation/x86/index.rst @@ -13,3 +13,4 @@ Linux x86 Support exception-tables kernel-stacks entry_64 + earlyprintk -- 2.20.1