From ff61f0791ce969d2db6c9f3b71d74ceec0a2e958 Mon Sep 17 00:00:00 2001
From: Jonathan Corbet <corbet@lwn.net>
Date: Tue, 14 Mar 2023 17:06:44 -0600
Subject: docs: move x86 documentation into Documentation/arch/

Move the x86 documentation under Documentation/arch/ as a way of cleaning
up the top-level directory and making the structure of our docs more
closely match the structure of the source directories it describes.

All in-kernel references to the old paths have been updated.

Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: linux-arch@vger.kernel.org
Cc: x86@kernel.org
Cc: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/lkml/20230315211523.108836-1-corbet@lwn.net/
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 Documentation/x86/earlyprintk.rst | 151 --------------------------------------
 1 file changed, 151 deletions(-)
 delete mode 100644 Documentation/x86/earlyprintk.rst

(limited to 'Documentation/x86/earlyprintk.rst')

diff --git a/Documentation/x86/earlyprintk.rst b/Documentation/x86/earlyprintk.rst
deleted file mode 100644
index 51ef11e8f725..000000000000
--- a/Documentation/x86/earlyprintk.rst
+++ /dev/null
@@ -1,151 +0,0 @@
-.. 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
-two USB cables, connected like this::
-
-  [host/target] <-------> [USB debug key] <-------> [client/console]
-
-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- <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
-       ...
-
-     .. 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:
-
-        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.
-
-  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
-     port and the NetChip device will only work as an early printk
-     device in this port.  The EHCI host controllers are electrically
-     wired such that the EHCI debug controller is hooked up to the
-     first physical port and there is no way to change this via software.
-     You can find the physical port through experimentation by trying
-     each physical port on the system and rebooting.  Or you can try
-     and use lsusb or look at the kernel info messages emitted by the
-     usb stack when you plug a usb device into various ports on the
-     "host/target" system.
-
-     Some hardware vendors do not expose the usb debug port with a
-     physical connector and if you find such a device send a complaint
-     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
-     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.
-
-Software requirements
-=====================
-
-  a) On the host/target system:
-
-    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".
-
-    .. 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
-    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
-=======
-
-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.
-- 
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