1Command syntax extensions for the new uImage format
2===================================================
3
4Author: Bartlomiej Sieka <tur@semihalf.com>
5
6With the introduction of the new uImage format, bootm command (and other
7commands as well) have to understand new syntax of the arguments. This is
8necessary in order to specify objects contained in the new uImage, on which
9bootm has to operate. This note attempts to first summarize bootm usage
10scenarios, and then introduces new argument syntax.
11
12
13bootm usage scenarios
14---------------------
15
16Below is a summary of bootm usage scenarios, focused on booting a PowerPC
17Linux kernel. The purpose of the following list is to document a complete list
18of supported bootm usages.
19
20Note: U-Boot supports two methods of booting a PowerPC Linux kernel: old way,
21i.e., without passing the Flattened Device Tree (FDT), and new way, where the
22kernel is passed a pointer to the FDT. The boot method is indicated for each
23scenario.
24
25
261.  bootm		boot image at the current address, equivalent to 2,3,8
27
28Old uImage:
292.  bootm <addr1>		    /* single image at <addr1> */
303.  bootm <addr1>		    /* multi-image at <addr1>  */
314.  bootm <addr1> -		    /* multi-image at <addr1>  */
325.  bootm <addr1> <addr2>	    /* single image at <addr1> */
336.  bootm <addr1> <addr2> <addr3>   /* single image at <addr1> */
347.  bootm <addr1> -	  <addr3>   /* single image at <addr1> */
35
36New uImage:
378.  bootm <addr1>
389.  bootm [<addr1>]:<subimg1>
3910. bootm [<addr1>]#<conf>
4011. bootm [<addr1>]:<subimg1> [<addr2>]:<subimg2>
4112. bootm [<addr1>]:<subimg1> [<addr2>]:<subimg2> [<addr3>]:<subimg3>
4213. bootm [<addr1>]:<subimg1> [<addr2>]:<subimg2> <addr3>
4314. bootm [<addr1>]:<subimg1> -			  [<addr3>]:<subimg3>
4415. bootm [<addr1>]:<subimg1> -			  <addr3>
45
46
47Ad. 1. This is equivalent to cases 2,3,8, depending on the type of image at
48the current image address.
49- boot method: see cases 2,3,8
50
51Ad. 2. Boot kernel image located at <addr1>.
52- boot method: non-FDT
53
54Ad. 3. First and second components of the image at <addr1> are assumed to be a
55kernel and a ramdisk, respectively. The kernel is booted with initrd loaded
56with the ramdisk from the image.
57- boot method: depends on the number of components at <addr1>, and on whether
58  U-Boot is compiled with OF support:
59
60		    |	       2 components |	       3 components |
61		    |	   (kernel, initrd) | (kernel, initrd, fdt) |
62---------------------------------------------------------------------
63#ifdef CONFIG_OF_*  |		    non-FDT |			FDT |
64#ifndef CONFIG_OF_* |		    non-FDT |		    non-FDT |
65
66Ad. 4. Similar to case 3, but the kernel is booted without initrd.  Second
67component of the multi-image is irrelevant (it can be a dummy, 1-byte file).
68- boot method: see case 3
69
70Ad. 5. Boot kernel image located at <addr1> with initrd loaded with ramdisk
71from the image at <addr2>.
72- boot method: non-FDT
73
74Ad. 6. <addr1> is the address of a kernel image, <addr2> is the address of a
75ramdisk image, and <addr3> is the address of a FDT binary blob.  Kernel is
76booted with initrd loaded with ramdisk from the image at <addr2>.
77- boot method: FDT
78
79Ad. 7. <addr1> is the address of a kernel image and <addr3> is the address of
80a FDT binary blob. Kernel is booted without initrd.
81- boot method: FDT
82
83Ad. 8. Image at <addr1> is assumed to contain a default configuration, which
84is booted.
85- boot method: FDT or non-FDT, depending on whether the default configuration
86  defines FDT
87
88Ad. 9. Similar to case 2: boot kernel stored in <subimg1> from the image at
89address <addr1>.
90- boot method: non-FDT
91
92Ad. 10. Boot configuration <conf> from the image at <addr1>.
93- boot method: FDT or non-FDT, depending on whether the configuration given
94  defines FDT
95
96Ad. 11. Equivalent to case 5: boot kernel stored in <subimg1> from the image
97at <addr1> with initrd loaded with ramdisk <subimg2> from the image at
98<addr2>.
99- boot method: non-FDT
100
101Ad. 12. Equivalent to case 6: boot kernel stored in <subimg1> from the image
102at <addr1> with initrd loaded with ramdisk <subimg2> from the image at
103<addr2>, and pass FDT blob <subimg3> from the image at <addr3>.
104- boot method: FDT
105
106Ad. 13. Similar to case 12, the difference being that <addr3> is the address
107of FDT binary blob that is to be passed to the kernel.
108- boot method: FDT
109
110Ad. 14. Equivalent to case 7: boot kernel stored in <subimg1> from the image
111at <addr1>, without initrd, and pass FDT blob <subimg3> from the image at
112<addr3>.
113- boot method: FDT
114
115Ad. 15. Similar to case 14, the difference being that <addr3> is the address
116of the FDT binary blob that is to be passed to the kernel.
117- boot method: FDT
118
119
120New uImage argument syntax
121--------------------------
122
123New uImage support introduces two new forms for bootm arguments, with the
124following syntax:
125
126- new uImage sub-image specification
127<addr>:<sub-image unit_name>
128
129- new uImage configuration specification
130<addr>#<configuration unit_name>
131
132
133Examples:
134
135- boot kernel "kernel@1" stored in a new uImage located at 200000:
136bootm 200000:kernel@1
137
138- boot configuration "cfg@1" from a new uImage located at 200000:
139bootm 200000#cfg@1
140
141- boot "kernel@1" from a new uImage at 200000 with initrd "ramdisk@2" found in
142  some other new uImage stored at address 800000:
143bootm 200000:kernel@1 800000:ramdisk@2
144
145- boot "kernel@2" from a new uImage at 200000, with initrd "ramdisk@1" and FDT
146  "fdt@1", both stored in some other new uImage located at 800000:
147bootm 200000:kernel@1 800000:ramdisk@1 800000:fdt@1
148
149- boot kernel "kernel@2" with initrd "ramdisk@2", both stored in a new uImage
150  at address 200000, with a raw FDT blob stored at address 600000:
151bootm 200000:kernel@2 200000:ramdisk@2 600000
152
153- boot kernel "kernel@2" from new uImage at 200000 with FDT "fdt@1" from the
154  same new uImage:
155bootm 200000:kernel@2 - 200000:fdt@1
156
157
158Note on current image address
159-----------------------------
160
161When bootm is called without arguments, the image at current image address is
162booted. The current image address is the address set most recently by a load
163command, etc, and is by default equal to CONFIG_SYS_LOAD_ADDR. For example, consider
164the following commands:
165
166tftp 200000 /tftpboot/kernel
167bootm
168Last command is equivalent to:
169bootm 200000
170
171In case of the new uImage argument syntax, the address portion of any argument
172can be omitted. If <addr3> is omitted, then it is assumed that image at
173<addr2> should be used. Similarly, when <addr2> is omitted, is is assumed that
174image at <addr1> should be used. If <addr1> is omitted, it is assumed that the
175current image address is to be used. For example, consider the following
176commands:
177
178tftp 200000 /tftpboot/uImage
179bootm :kernel@1
180Last command is equivalent to:
181bootm 200000:kernel@1
182
183tftp 200000 /tftpboot/uImage
184bootm 400000:kernel@1 :ramdisk@1
185Last command is equivalent to:
186bootm 400000:kernel@1 400000:ramdisk@1
187
188tftp 200000 /tftpboot/uImage
189bootm :kernel@1 400000:ramdisk@1 :fdt@1
190Last command is equivalent to:
191bootm 200000:kernel@1 400000:ramdisk@1 400000:fdt@1
192