mirror of
https://github.com/torvalds/linux.git
synced 2024-12-05 18:41:23 +00:00
1b3c3714cb
heirarchical, hierachical -> hierarchical heirarchy, hierachy -> hierarchy Signed-off-by: Uwe Kleine-König <zeisberg@informatik.uni-freiburg.de> Signed-off-by: Adrian Bunk <bunk@stusta.de>
281 lines
10 KiB
Plaintext
281 lines
10 KiB
Plaintext
|
|
Adding a new board to LinuxSH
|
|
================================
|
|
|
|
Paul Mundt <lethal@linux-sh.org>
|
|
|
|
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
|
|
hierarchy 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 ...
|
|
|
|
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
|
|
should also add a directory in include/asm-sh for headers localized to this
|
|
board (if there are going to be more than one). 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 (via incdir-y
|
|
overloading), 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/ hierarchy. 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>
|
|
#include <asm/rtc.h> /* for board_time_init() */
|
|
|
|
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.
|
|
|
|
machvec functions fall into a number of categories:
|
|
|
|
- I/O functions to IO memory (inb etc) and PCI/main memory (readb etc).
|
|
- I/O mapping functions (ioport_map, ioport_unmap, etc).
|
|
- a 'heartbeat' function.
|
|
- PCI and IRQ initialization routines.
|
|
- Consistent allocators (for boards that need special allocators,
|
|
particularly for allocating out of some board-specific SRAM for DMA
|
|
handles).
|
|
|
|
There are machvec functions added and removed over time, so always be sure to
|
|
consult include/asm-sh/machvec.h for the current state of the machvec.
|
|
|
|
The kernel will automatically wrap in generic routines for undefined function
|
|
pointers in the machvec at boot time, as machvec functions are referenced
|
|
unconditionally throughout most of the tree. Some boards have incredibly
|
|
sparse machvecs (such as the dreamcast and sh03), whereas others must define
|
|
virtually everything (rts7751r2d).
|
|
|
|
Adding a new machine is relatively trivial (using vapor as an example):
|
|
|
|
If the board-specific definitions are quite minimalistic, as is the case for
|
|
the vast majority of boards, simply having a single board-specific header is
|
|
sufficient.
|
|
|
|
- add a new file include/asm-sh/vapor.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.
|
|
|
|
Note that these prototypes are generated automatically by setting
|
|
__IO_PREFIX to something sensible. A typical example would be:
|
|
|
|
#define __IO_PREFIX vapor
|
|
#include <asm/io_generic.h>
|
|
|
|
somewhere in the board-specific header. Any boards being ported that still
|
|
have a legacy io.h should remove it entirely and switch to the new model.
|
|
|
|
- Add machine vector definitions to the board's setup.c. At a bare minimum,
|
|
this must be defined as something like:
|
|
|
|
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 (if there are enough to warrant it).
|
|
|
|
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
|
|
board.
|