1 .. SPDX-License-Identifier: GPL-2.0
2
3 =============================
4 Adding a new board to LinuxSH
5 =============================
6
7 Paul Mundt <lethal@linux-sh.org>
8
9 This document attempts to outline what steps a
10 for new boards to the LinuxSH port under the n
11 also attempts to outline some of the noticeabl
12 and the 2.5/2.6 SH backend.
13
14 1. New Directory Structure
15 ==========================
16
17 The first thing to note is the new directory s
18 of the board-specific code (with the exception
19 in arch/sh/kernel/ directly, with board-specif
20 include/asm-sh/. For the new kernel, things ar
21 companion chip type, and CPU type. Looking at
22 hierarchy looks like the following:
23
24 Board-specific code::
25
26 .
27 |-- arch
28 | `-- sh
29 | `-- boards
30 | |-- adx
31 | | `-- board-specific files
32 | |-- bigsur
33 | | `-- board-specific files
34 | |
35 | ... more boards here ...
36 |
37 `-- include
38 `-- asm-sh
39 |-- adx
40 | `-- board-specific headers
41 |-- bigsur
42 | `-- board-specific headers
43 |
44 .. more boards here ...
45
46 Next, for companion chips::
47
48 .
49 `-- arch
50 `-- sh
51 `-- cchips
52 `-- hd6446x
53 `-- hd64461
54 `-- cchip-specific fil
55
56 ... and so on. Headers for the companion chips
57 board-specific headers. Thus, include/asm-sh/h
58 hd64461-specific headers.
59
60 Finally, CPU family support is also abstracted
61
62 .
63 |-- arch
64 | `-- sh
65 | |-- kernel
66 | | `-- cpu
67 | | |-- sh2
68 | | | `-- SH-2 generic files
69 | | |-- sh3
70 | | | `-- SH-3 generic files
71 | | `-- sh4
72 | | `-- SH-4 generic files
73 | `-- mm
74 | `-- This is also broken out pe
75 | have their own set of cach
76 |
77 `-- include
78 `-- asm-sh
79 |-- cpu-sh2
80 | `-- SH-2 specific headers
81 |-- cpu-sh3
82 | `-- SH-3 specific headers
83 `-- cpu-sh4
84 `-- SH-4 specific headers
85
86 It should be noted that CPU subtypes are _not_
87 need to be dealt with by the CPU family specif
88
89 2. Adding a New Board
90 =====================
91
92 The first thing to determine is whether the bo
93 isolated, or whether it will be part of a fami
94 share the same board-specific code with minor
95
96 In the first case, this is just a matter of ma
97 board in arch/sh/boards/ and adding rules to h
98 build system (more on this in the next section
99 it makes more sense to have a common top-level
100 and then populate that with sub-directories fo
101 Both the Solution Engine and the hp6xx boards
102
103 After you have setup your new arch/sh/boards/
104 should also add a directory in include/asm-sh
105 board (if there are going to be more than one)
106 seamlessly with the build system, it's best to
107 as the arch/sh/boards/ directory name, though
108 a family, the build system has ways of dealing
109 overloading), and you can feel free to name th
110 member itself.
111
112 There are a few things that each board is requ
113 arch/sh/boards and the include/asm-sh/ hierarc
114 explain this, we use some examples for adding
115 setup code, we're required at the very least t
116 get_system_type() and platform_setup(). For ou
117 might look something like::
118
119 /*
120 * arch/sh/boards/vapor/setup.c - Setup cod
121 */
122 #include <linux/init.h>
123
124 const char *get_system_type(void)
125 {
126 return "FooTech Vaporboard";
127 }
128
129 int __init platform_setup(void)
130 {
131 /*
132 * If our hardware actually existed
133 * setup here. Though it's also san
134 * if there's no real init work tha
135 * this board.
136 */
137
138 /* Start-up imaginary PCI ... */
139
140 /* And whatever else ... */
141
142 return 0;
143 }
144
145 Our new imaginary board will also have to tie
146 to be of any use.
147
148 machvec functions fall into a number of catego
149
150 - I/O functions to IO memory (inb etc) and PC
151 - I/O mapping functions (ioport_map, ioport_u
152 - a 'heartbeat' function.
153 - PCI and IRQ initialization routines.
154 - Consistent allocators (for boards that need
155 particularly for allocating out of some boa
156 handles).
157
158 There are machvec functions added and removed
159 consult include/asm-sh/machvec.h for the curre
160
161 The kernel will automatically wrap in generic
162 pointers in the machvec at boot time, as machv
163 unconditionally throughout most of the tree. S
164 sparse machvecs (such as the dreamcast and sh0
165 virtually everything (rts7751r2d).
166
167 Adding a new machine is relatively trivial (us
168
169 If the board-specific definitions are quite mi
170 the vast majority of boards, simply having a s
171 sufficient.
172
173 - add a new file include/asm-sh/vapor.h which
174 any machine specific IO functions prefixed
175 example vapor_inb. These will be needed whe
176 vector.
177
178 Note that these prototypes are generated au
179 __IO_PREFIX to something sensible. A typica
180
181 #define __IO_PREFIX vapor
182 #include <asm/io_generic.h>
183
184 somewhere in the board-specific header. Any
185 have a legacy io.h should remove it entirel
186
187 - Add machine vector definitions to the board
188 this must be defined as something like::
189
190 struct sh_machine_vector mv_vapor __in
191 .mv_name = "vapor",
192 };
193 ALIAS_MV(vapor)
194
195 - finally add a file arch/sh/boards/vapor/io.
196 the machine specific io functions (if there
197
198 3. Hooking into the Build System
199 ================================
200
201 Now that we have the corresponding directories
202 board-specific code is in place, it's time to
203 whole mess to fit into the build system.
204
205 Large portions of the build system are now ent
206 require the proper entry here and there in ord
207
208 The first thing to do is to add an entry to ar
209 "System type" menu::
210
211 config SH_VAPOR
212 bool "Vapor"
213 help
214 select Vapor if configuring for a
215
216 next, this has to be added into arch/sh/Makefi
217 machdir-y entry in order to be built. This ent
218 the board directory as it appears in arch/sh/b
219 sub-directory (in which case, all parent direc
220 need to be listed). For our new board, this en
221
222 machdir-$(CONFIG_SH_VAPOR) += vapor
223
224 provided that we've placed everything in the a
225
226 Next, the build system assumes that your inclu
227 be named the same. If this is not the case (as
228 boards belonging to a common family), then the
229 implicitly appended to incdir-y. The existing
230 Solution Engine and hp6xx boards, so see these
231
232 Once that is taken care of, it's time to add a
233 This is done by adding an entry to the end of
234 list. The method for doing this is self explan
235 space restating it here. After this is done, y
236 implicit checks for your board if you need thi
237 common code, such as::
238
239 /* Make sure we're on the FooTech Vapo
240 if (!mach_is_vapor())
241 return -ENODEV;
242
243 also note that the mach_is_boardname() check w
244 lowercase, regardless of the fact that the mac
245 uppercase. You can read the script if you real
246 so you probably don't want to do that.
247
248 Now all that's left to do is providing a defco
249 way, other people who end up with this board c
250 for reference instead of trying to guess what
251 used on it.
252
253 Also, as soon as you have copied over a sample
254 (assume arch/sh/configs/vapor_defconfig), you
255 build target, and it will be implicitly listed
256
257 Looking at the 'make help' output, you should
258
259 Architecture specific targets (sh):
260
261 ======================= ==================
262 zImage Compressed kernel
263 adx_defconfig Build for adx
264 cqreek_defconfig Build for cqreek
265 dreamcast_defconfig Build for dreamcas
266 ...
267 vapor_defconfig Build for vapor
268 ======================= ==================
269
270 which then allows you to do::
271
272 $ make ARCH=sh CROSS_COMPILE=sh4-linux- va
273
274 which will in turn copy the defconfig for this
275 oldconfig (prompting you for any new options s
276 and start you on your way to having a function
277 board.
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