tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1 =========================
2 BOOTING FR-V LINUX KERNEL
3 =========================
4
5======================
6PROVIDING A FILESYSTEM
7======================
8
9First of all, a root filesystem must be made available. This can be done in
10one of two ways:
11
12 (1) NFS Export
13
14 A filesystem should be constructed in a directory on an NFS server that
15 the target board can reach. This directory should then be NFS exported
16 such that the target board can read and write into it as root.
17
18 (2) Flash Filesystem (JFFS2 Recommended)
19
20 In this case, the image must be stored or built up on flash before it
21 can be used. A complete image can be built using the mkfs.jffs2 or
22 similar program and then downloaded and stored into flash by RedBoot.
23
24
25========================
26LOADING THE KERNEL IMAGE
27========================
28
29The kernel will need to be loaded into RAM by RedBoot (or by some alternative
30boot loader) before it can be run. The kernel image (arch/frv/boot/Image) may
31be loaded in one of three ways:
32
33 (1) Load from Flash
34
35 This is the simplest. RedBoot can store an image in the flash (see the
36 RedBoot documentation) and then load it back into RAM. RedBoot keeps
37 track of the load address, entry point and size, so the command to do
38 this is simply:
39
40 fis load linux
41
42 The image is then ready to be executed.
43
44 (2) Load by TFTP
45
46 The following command will download a raw binary kernel image from the
47 default server (as negotiated by BOOTP) and store it into RAM:
48
49 load -b 0x00100000 -r /tftpboot/image.bin
50
51 The image is then ready to be executed.
52
53 (3) Load by Y-Modem
54
55 The following command will download a raw binary kernel image across the
56 serial port that RedBoot is currently using:
57
58 load -m ymodem -b 0x00100000 -r zImage
59
60 The serial client (such as minicom) must then be told to transmit the
61 program by Y-Modem.
62
63 When finished, the image will then be ready to be executed.
64
65
66==================
67BOOTING THE KERNEL
68==================
69
70Boot the image with the following RedBoot command:
71
72 exec -c "<CMDLINE>" 0x00100000
73
74For example:
75
76 exec -c "console=ttySM0,115200 ip=:::::dhcp root=/dev/mtdblock2 rw"
77
78This will start the kernel running. Note that if the GDB-stub is compiled in,
79then the kernel will immediately wait for GDB to connect over serial before
80doing anything else. See the section on kernel debugging with GDB.
81
82The kernel command line <CMDLINE> tells the kernel where its console is and
83how to find its root filesystem. This is made up of the following components,
84separated by spaces:
85
86 (*) console=ttyS<x>[,<baud>[<parity>[<bits>[<flow>]]]]
87
88 This specifies that the system console should output through on-chip
89 serial port <x> (which can be "0" or "1").
90
91 <baud> is a standard baud rate between 1200 and 115200 (default 9600).
92
93 <parity> is a parity setting of "N", "O", "E", "M" or "S" for None, Odd,
94 Even, Mark or Space. "None" is the default.
95
96 <stop> is "7" or "8" for the number of bits per character. "8" is the
97 default.
98
99 <flow> is "r" to use flow control (XCTS on serial port 2 only). The
100 default is to not use flow control.
101
102 For example:
103
104 console=ttyS0,115200
105
106 To use the first on-chip serial port at baud rate 115200, no parity, 8
107 bits, and no flow control.
108
109 (*) root=/dev/<xxxx>
110
111 This specifies the device upon which the root filesystem resides. For
112 example:
113
114 /dev/nfs NFS root filesystem
115 /dev/mtdblock3 Fourth RedBoot partition on the System Flash
116
117 (*) rw
118
119 Start with the root filesystem mounted Read/Write.
120
121 The remaining components are all optional:
122
123 (*) ip=<ip>::::<host>:<iface>:<cfg>
124
125 Configure the network interface. If <cfg> is "off" then <ip> should
126 specify the IP address for the network device <iface>. <host> provide
127 the hostname for the device.
128
129 If <cfg> is "bootp" or "dhcp", then all of these parameters will be
130 discovered by consulting a BOOTP or DHCP server.
131
132 For example, the following might be used:
133
134 ip=192.168.73.12::::frv:eth0:off
135
136 This sets the IP address on the VDK motherboard RTL8029 ethernet chipset
137 (eth0) to be 192.168.73.12, and sets the board's hostname to be "frv".
138
139 (*) nfsroot=<server>:<dir>[,v<vers>]
140
141 This is mandatory if "root=/dev/nfs" is given as an option. It tells the
142 kernel the IP address of the NFS server providing its root filesystem,
143 and the pathname on that server of the filesystem.
144
145 The NFS version to use can also be specified. v2 and v3 are supported by
146 Linux.
147
148 For example:
149
150 nfsroot=192.168.73.1:/nfsroot-frv
151
152 (*) profile=1
153
154 Turns on the kernel profiler (accessible through /proc/profile).
155
156 (*) console=gdb0
157
158 This can be used as an alternative to the "console=ttyS..." listed
159 above. I tells the kernel to pass the console output to GDB if the
160 gdbstub is compiled in to the kernel.
161
162 If this is used, then the gdbstub passes the text to GDB, which then
163 simply dumps it to its standard output.
164
165 (*) mem=<xxx>M
166
167 Normally the kernel will work out how much SDRAM it has by reading the
168 SDRAM controller registers. That can be overridden with this
169 option. This allows the kernel to be told that it has <xxx> megabytes of
170 memory available.
171
172 (*) init=<prog> [<arg> [<arg> [<arg> ...]]]
173
174 This tells the kernel what program to run initially. By default this is
175 /sbin/init, but /sbin/sash or /bin/sh are common alternatives.
176
177 (*) vdc=...
178
179 This option configures the MB93493 companion chip visual display
180 driver. Please see Documentation/frv/mb93493/vdc.txt for more
181 information.