path: root/Documentation/sh
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authorLinus Torvalds <>2005-04-16 15:20:36 -0700
committerLinus Torvalds <>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/sh
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'Documentation/sh')
2 files changed, 485 insertions, 0 deletions
diff --git a/Documentation/sh/kgdb.txt b/Documentation/sh/kgdb.txt
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+This file describes the configuration and behavior of KGDB for the SH
+kernel. Based on a description from Henry Bell <>, it
+has been modified to account for quirks in the current implementation.
+This version of KGDB was written for 2.4.xx kernels for the SH architecture.
+Further documentation is available from the linux-sh project website.
+Debugging Setup: Host
+The two machines will be connected together via a serial line - this
+should be a null modem cable i.e. with a twist.
+On your DEVELOPMENT machine, go to your kernel source directory and
+build the kernel, enabling KGDB support in the "kernel hacking" section.
+This includes the KGDB code, and also makes the kernel be compiled with
+the "-g" option set -- necessary for debugging.
+To install this new kernel, use the following installation procedure.
+Decide on which tty port you want the machines to communicate, then
+cable them up back-to-back using the null modem. On the DEVELOPMENT
+machine, you may wish to create an initialization file called .gdbinit
+(in the kernel source directory or in your home directory) to execute
+commonly-used commands at startup.
+A minimal .gdbinit might look like this:
+ file vmlinux
+ set remotebaud 115200
+ target remote /dev/ttyS0
+Change the "target" definition so that it specifies the tty port that
+you intend to use. Change the "remotebaud" definition to match the
+data rate that you are going to use for the com line (115200 is the
+Debugging Setup: Target
+By default, the KGDB stub will communicate with the host GDB using
+ttySC1 at 115200 baud, 8 databits, no parity; these defaults can be
+changed in the kernel configuration. As the kernel starts up, KGDB will
+initialize so that breakpoints, kernel segfaults, and so forth will
+generally enter the debugger.
+This behavior can be modified by including the "kgdb" option in the
+kernel command line; this option has the general form:
+ kgdb=<ttyspec>,<action>
+The <ttyspec> indicates the port to use, and can optionally specify
+baud, parity and databits -- e.g. "ttySC0,9600N8" or "ttySC1,19200".
+The <action> can be "halt" or "disabled". The "halt" action enters the
+debugger via a breakpoint as soon as kgdb is initialized; the "disabled"
+action causes kgdb to ignore kernel segfaults and such until explicitly
+entered by a breakpoint in the code or by external action (sysrq or NMI).
+(Both <ttyspec> and <action> can appear alone, w/o the separating comma.)
+For example, if you wish to debug early in kernel startup code, you
+might specify the halt option:
+ kgdb=halt
+Boot the TARGET machinem, which will appear to hang.
+On your DEVELOPMENT machine, cd to the source directory and run the gdb
+program. (This is likely to be a cross GDB which runs on your host but
+is built for an SH target.) If everything is working correctly you
+should see gdb print out a few lines indicating that a breakpoint has
+been taken. It will actually show a line of code in the target kernel
+inside the gdbstub activation code.
+NOTE: BE SURE TO TERMINATE OR SUSPEND any other host application which
+may be using the same serial port (for example, a terminal emulator you
+have been using to connect to the target boot code.) Otherwise, data
+from the target may not all get to GDB!
+You can now use whatever gdb commands you like to set breakpoints.
+Enter "continue" to start your target machine executing again. At this
+point the target system will run at full speed until it encounters
+your breakpoint or gets a segment violation in the kernel, or whatever.
+Serial Ports: KGDB, Console
+This version of KGDB may not gracefully handle conflict with other
+drivers in the kernel using the same port. If KGDB is configured on the
+same port (and with the same parameters) as the kernel console, or if
+CONFIG_SH_KGDB_CONSOLE is configured, things should be fine (though in
+some cases console messages may appear twice through GDB). But if the
+KGDB port is not the kernel console and used by another serial driver
+which assumes different serial parameters (e.g. baud rate) KGDB may not
+Also, when KGDB is entered via sysrq-g (requires CONFIG_KGDB_SYSRQ) and
+the kgdb port uses the same port as the console, detaching GDB will not
+restore the console to working order without the port being re-opened.
+Another serious consequence of this is that GDB currently CANNOT break
+into KGDB externally (e.g. via ^C or <BREAK>); unless a breakpoint or
+error is encountered, the only way to enter KGDB after the initial halt
+(see above) is via NMI (CONFIG_KGDB_NMI) or sysrq-g (CONFIG_KGDB_SYSRQ).
+Code is included for the basic Hitachi Solution Engine boards to allow
+the use of ttyS0 for KGDB if desired; this is less robust, but may be
+useful in some cases. (This cannot be selected using the config file,
+but only through the kernel command line, e.g. "kgdb=ttyS0", though the
+configured defaults for baud rate etc. still apply if not overridden.)
+If gdbstub Does Not Work
+If it doesn't work, you will have to troubleshoot it. Do the easy
+things first like double checking your cabling and data rates. You
+might try some non-kernel based programs to see if the back-to-back
+connection works properly. Just something simple like cat /etc/hosts
+/dev/ttyS0 on one machine and cat /dev/ttyS0 on the other will tell you
+if you can send data from one machine to the other. There is no point
+in tearing out your hair in the kernel if the line doesn't work.
+If you need to debug the GDB/KGDB communication itself, the gdb commands
+"set debug remote 1" and "set debug serial 1" may be useful, but be
+warned: they produce a lot of output.
+Each process in a target machine is seen as a gdb thread. gdb thread related
+commands (info threads, thread n) can be used. CONFIG_KGDB_THREAD must
+be defined for this to work.
+In this version, kgdb reports PID_MAX (32768) as the process ID for the
+idle process (pid 0), since GDB does not accept 0 as an ID.
+Detaching (exiting KGDB)
+There are two ways to resume full-speed target execution: "continue" and
+"detach". With "continue", GDB inserts any specified breakpoints in the
+target code and resumes execution; the target is still in "gdb mode".
+If a breakpoint or other debug event (e.g. NMI) happens, the target
+halts and communicates with GDB again, which is waiting for it.
+With "detach", GDB does *not* insert any breakpoints; target execution
+is resumed and GDB stops communicating (does not wait for the target).
+In this case, the target is no longer in "gdb mode" -- for example,
+console messages no longer get sent separately to the KGDB port, or
+encapsulated for GDB. If a debug event (e.g. NMI) occurs, the target
+will re-enter "gdb mode" and will display this fact on the console; you
+must give a new "target remote" command to gdb.
+THE KGDB PORT AFTER A DETACH COMMAND. For example, after the detach you
+could start a terminal emulator on the same host port and enter a <cr>;
+however, this program must then be terminated or suspended in order to
+use GBD again if KGDB is re-entered.
+This code was mostly generated by Henry Bell <>;
+largely from KGDB by Amit S. Kale <> - extracts from
+code by Glenn Engel, Jim Kingdon, David Grothe <>, Tigran
+Aivazian <>, William Gatliff <>, Ben
+Lee, Steve Chamberlain and Benoit Miller <> are also
+Jeremy Siegel
diff --git a/Documentation/sh/new-machine.txt b/Documentation/sh/new-machine.txt
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@@ -0,0 +1,306 @@
+ Adding a new board to LinuxSH
+ ================================
+ Paul Mundt <>
+This document attempts to outline what steps are necessary to add support
+for new boards to the LinuxSH port under the new 2.5 and 2.6 kernels. This
+also attempts to outline some of the noticeable changes between the 2.4
+and the 2.5/2.6 SH backend.
+1. New Directory Structure
+The first thing to note is the new directory structure. Under 2.4, most
+of the board-specific code (with the exception of stboards) ended up
+in arch/sh/kernel/ directly, with board-specific headers ending up in
+include/asm-sh/. For the new kernel, things are broken out by board type,
+companion chip type, and CPU type. Looking at a tree view of this directory
+heirarchy looks like the following:
+Board-specific code:
+|-- arch
+| `-- sh
+| `-- boards
+| |-- adx
+| | `-- board-specific files
+| |-- bigsur
+| | `-- board-specific files
+| |
+| ... more boards here ...
+`-- include
+ `-- asm-sh
+ |-- adx
+ | `-- board-specific headers
+ |-- bigsur
+ | `-- board-specific headers
+ |
+ .. more boards here ...
+It should also be noted that each board is required to have some certain
+headers. At the time of this writing, io.h is the only thing that needs
+to be provided for each board, and can generally just reference generic
+functions (with the exception of isa_port2addr).
+Next, for companion chips:
+`-- arch
+ `-- sh
+ `-- cchips
+ `-- hd6446x
+ |-- hd64461
+ | `-- cchip-specific files
+ `-- hd64465
+ `-- cchip-specific files
+... and so on. Headers for the companion chips are treated the same way as
+board-specific headers. Thus, include/asm-sh/hd64461 is home to all of the
+hd64461-specific headers.
+Finally, CPU family support is also abstracted:
+|-- arch
+| `-- sh
+| |-- kernel
+| | `-- cpu
+| | |-- sh2
+| | | `-- SH-2 generic files
+| | |-- sh3
+| | | `-- SH-3 generic files
+| | `-- sh4
+| | `-- SH-4 generic files
+| `-- mm
+| `-- This is also broken out per CPU family, so each family can
+| have their own set of cache/tlb functions.
+`-- include
+ `-- asm-sh
+ |-- cpu-sh2
+ | `-- SH-2 specific headers
+ |-- cpu-sh3
+ | `-- SH-3 specific headers
+ `-- cpu-sh4
+ `-- SH-4 specific headers
+It should be noted that CPU subtypes are _not_ abstracted. Thus, these still
+need to be dealt with by the CPU family specific code.
+2. Adding a New Board
+The first thing to determine is whether the board you are adding will be
+isolated, or whether it will be part of a family of boards that can mostly
+share the same board-specific code with minor differences.
+In the first case, this is just a matter of making a directory for your
+board in arch/sh/boards/ and adding rules to hook your board in with the
+build system (more on this in the next section). However, for board families
+it makes more sense to have a common top-level arch/sh/boards/ directory
+and then populate that with sub-directories for each member of the family.
+Both the Solution Engine and the hp6xx boards are an example of this.
+After you have setup your new arch/sh/boards/ directory, remember that you
+also must add a directory in include/asm-sh for headers localized to this
+board. In order to interoperate seamlessly with the build system, it's best
+to have this directory the same as the arch/sh/boards/ directory name,
+though if your board is again part of a family, the build system has ways
+of dealing with this, and you can feel free to name the directory after
+the family member itself.
+There are a few things that each board is required to have, both in the
+arch/sh/boards and the include/asm-sh/ heirarchy. In order to better
+explain this, we use some examples for adding an imaginary board. For
+setup code, we're required at the very least to provide definitions for
+get_system_type() and platform_setup(). For our imaginary board, this
+might look something like:
+ * arch/sh/boards/vapor/setup.c - Setup code for imaginary board
+ */
+#include <linux/init.h>
+const char *get_system_type(void)
+ return "FooTech Vaporboard";
+int __init platform_setup(void)
+ /*
+ * If our hardware actually existed, we would do real
+ * setup here. Though it's also sane to leave this empty
+ * if there's no real init work that has to be done for
+ * this board.
+ */
+ /*
+ * Presume all FooTech boards have the same broken timer,
+ * and also presume that we've defined foo_timer_init to
+ * do something useful.
+ */
+ board_time_init = foo_timer_init;
+ /* Start-up imaginary PCI ... */
+ /* And whatever else ... */
+ return 0;
+Our new imaginary board will also have to tie into the machvec in order for it
+to be of any use. Currently the machvec is slowly on its way out, but is still
+required for the time being. As such, let us take a look at what needs to be
+done for the machvec assignment.
+machvec functions fall into a number of categories:
+ - I/O functions to IO memory (inb etc) and PCI/main memory (readb etc).
+ - I/O remapping functions (ioremap etc)
+ - some initialisation functions
+ - a 'heartbeat' function
+ - some miscellaneous flags
+The tree can be built in two ways:
+ - as a fully generic build. All drivers are linked in, and all functions
+ go through the machvec
+ - as a machine specific build. In this case only the required drivers
+ will be linked in, and some macros may be redefined to not go through
+ the machvec where performance is important (in particular IO functions).
+There are three ways in which IO can be performed:
+ - none at all. This is really only useful for the 'unknown' machine type,
+ which us designed to run on a machine about which we know nothing, and
+ so all all IO instructions do nothing.
+ - fully custom. In this case all IO functions go to a machine specific
+ set of functions which can do what they like
+ - a generic set of functions. These will cope with most situations,
+ and rely on a single function, mv_port2addr, which is called through the
+ machine vector, and converts an IO address into a memory address, which
+ can be read from/written to directly.
+Thus adding a new machine involves the following steps (I will assume I am
+adding a machine called vapor):
+ - add a new file include/asm-sh/vapor/io.h which contains prototypes for
+ any machine specific IO functions prefixed with the machine name, for
+ example vapor_inb. These will be needed when filling out the machine
+ vector.
+ This is the minimum that is required, however there are ample
+ opportunities to optimise this. In particular, by making the prototypes
+ inline function definitions, it is possible to inline the function when
+ building machine specific versions. Note that the machine vector
+ functions will still be needed, so that a module built for a generic
+ setup can be loaded.
+ - add a new file arch/sh/boards/vapor/mach.c. This contains the definition
+ of the machine vector. When building the machine specific version, this
+ will be the real machine vector (via an alias), while in the generic
+ version is used to initialise the machine vector, and then freed, by
+ making it initdata. This should be defined as:
+ struct sh_machine_vector mv_vapor __initmv = {
+ .mv_name = "vapor",
+ }
+ ALIAS_MV(vapor)
+ - finally add a file arch/sh/boards/vapor/io.c, which contains
+ definitions of the machine specific io functions.
+A note about initialisation functions. Three initialisation functions are
+provided in the machine vector:
+ - mv_arch_init - called very early on from setup_arch
+ - mv_init_irq - called from init_IRQ, after the generic SH interrupt
+ initialisation
+ - mv_init_pci - currently not used
+Any other remaining functions which need to be called at start up can be
+added to the list using the __initcalls macro (or module_init if the code
+can be built as a module). Many generic drivers probe to see if the device
+they are targeting is present, however this may not always be appropriate,
+so a flag can be added to the machine vector which will be set on those
+machines which have the hardware in question, reducing the probe to a
+single conditional.
+3. Hooking into the Build System
+Now that we have the corresponding directories setup, and all of the
+board-specific code is in place, it's time to look at how to get the
+whole mess to fit into the build system.
+Large portions of the build system are now entirely dynamic, and merely
+require the proper entry here and there in order to get things done.
+The first thing to do is to add an entry to arch/sh/Kconfig, under the
+"System type" menu:
+config SH_VAPOR
+ bool "Vapor"
+ help
+ select Vapor if configuring for a FooTech Vaporboard.
+next, this has to be added into arch/sh/Makefile. All boards require a
+machdir-y entry in order to be built. This entry needs to be the name of
+the board directory as it appears in arch/sh/boards, even if it is in a
+sub-directory (in which case, all parent directories below arch/sh/boards/
+need to be listed). For our new board, this entry can look like:
+machdir-$(CONFIG_SH_VAPOR) += vapor
+provided that we've placed everything in the arch/sh/boards/vapor/ directory.
+Next, the build system assumes that your include/asm-sh directory will also
+be named the same. If this is not the case (as is the case with multiple
+boards belonging to a common family), then the directory name needs to be
+implicitly appended to incdir-y. The existing code manages this for the
+Solution Engine and hp6xx boards, so see these for an example.
+Once that is taken care of, it's time to add an entry for the mach type.
+This is done by adding an entry to the end of the arch/sh/tools/mach-types
+list. The method for doing this is self explanatory, and so we won't waste
+space restating it here. After this is done, you will be able to use
+implicit checks for your board if you need this somewhere throughout the
+common code, such as:
+ /* Make sure we're on the FooTech Vaporboard */
+ if (!mach_is_vapor())
+ return -ENODEV;
+also note that the mach_is_boardname() check will be implicitly forced to
+lowercase, regardless of the fact that the mach-types entries are all
+uppercase. You can read the script if you really care, but it's pretty ugly,
+so you probably don't want to do that.
+Now all that's left to do is providing a defconfig for your new board. This
+way, other people who end up with this board can simply use this config
+for reference instead of trying to guess what settings are supposed to be
+used on it.
+Also, as soon as you have copied over a sample .config for your new board
+(assume arch/sh/configs/vapor_defconfig), you can also use this directly as a
+build target, and it will be implicitly listed as such in the help text.
+Looking at the 'make help' output, you should now see something like:
+Architecture specific targets (sh):
+ zImage - Compressed kernel image (arch/sh/boot/zImage)
+ adx_defconfig - Build for adx
+ cqreek_defconfig - Build for cqreek
+ dreamcast_defconfig - Build for dreamcast
+ vapor_defconfig - Build for vapor
+which then allows you to do:
+$ make ARCH=sh CROSS_COMPILE=sh4-linux- vapor_defconfig vmlinux
+which will in turn copy the defconfig for this board, run it through
+oldconfig (prompting you for any new options since the time of creation),
+and start you on your way to having a functional kernel for your new