diff options
Diffstat (limited to 'Documentation/arm/Booting')
-rw-r--r-- | Documentation/arm/Booting | 33 |
1 files changed, 4 insertions, 29 deletions
diff --git a/Documentation/arm/Booting b/Documentation/arm/Booting index 4e686a2ed91e..76850295af8f 100644 --- a/Documentation/arm/Booting +++ b/Documentation/arm/Booting | |||
@@ -65,19 +65,13 @@ looks at the connected hardware is beyond the scope of this document. | |||
65 | The boot loader must ultimately be able to provide a MACH_TYPE_xxx | 65 | The boot loader must ultimately be able to provide a MACH_TYPE_xxx |
66 | value to the kernel. (see linux/arch/arm/tools/mach-types). | 66 | value to the kernel. (see linux/arch/arm/tools/mach-types). |
67 | 67 | ||
68 | 4. Setup boot data | 68 | |
69 | ------------------ | 69 | 4. Setup the kernel tagged list |
70 | ------------------------------- | ||
70 | 71 | ||
71 | Existing boot loaders: OPTIONAL, HIGHLY RECOMMENDED | 72 | Existing boot loaders: OPTIONAL, HIGHLY RECOMMENDED |
72 | New boot loaders: MANDATORY | 73 | New boot loaders: MANDATORY |
73 | 74 | ||
74 | The boot loader must provide either a tagged list or a dtb image for | ||
75 | passing configuration data to the kernel. The physical address of the | ||
76 | boot data is passed to the kernel in register r2. | ||
77 | |||
78 | 4a. Setup the kernel tagged list | ||
79 | -------------------------------- | ||
80 | |||
81 | The boot loader must create and initialise the kernel tagged list. | 75 | The boot loader must create and initialise the kernel tagged list. |
82 | A valid tagged list starts with ATAG_CORE and ends with ATAG_NONE. | 76 | A valid tagged list starts with ATAG_CORE and ends with ATAG_NONE. |
83 | The ATAG_CORE tag may or may not be empty. An empty ATAG_CORE tag | 77 | The ATAG_CORE tag may or may not be empty. An empty ATAG_CORE tag |
@@ -107,24 +101,6 @@ The tagged list must be placed in a region of memory where neither | |||
107 | the kernel decompressor nor initrd 'bootp' program will overwrite | 101 | the kernel decompressor nor initrd 'bootp' program will overwrite |
108 | it. The recommended placement is in the first 16KiB of RAM. | 102 | it. The recommended placement is in the first 16KiB of RAM. |
109 | 103 | ||
110 | 4b. Setup the device tree | ||
111 | ------------------------- | ||
112 | |||
113 | The boot loader must load a device tree image (dtb) into system ram | ||
114 | at a 64bit aligned address and initialize it with the boot data. The | ||
115 | dtb format is documented in Documentation/devicetree/booting-without-of.txt. | ||
116 | The kernel will look for the dtb magic value of 0xd00dfeed at the dtb | ||
117 | physical address to determine if a dtb has been passed instead of a | ||
118 | tagged list. | ||
119 | |||
120 | The boot loader must pass at a minimum the size and location of the | ||
121 | system memory, and the root filesystem location. The dtb must be | ||
122 | placed in a region of memory where the kernel decompressor will not | ||
123 | overwrite it. The recommended placement is in the first 16KiB of RAM | ||
124 | with the caveat that it may not be located at physical address 0 since | ||
125 | the kernel interprets a value of 0 in r2 to mean neither a tagged list | ||
126 | nor a dtb were passed. | ||
127 | |||
128 | 5. Calling the kernel image | 104 | 5. Calling the kernel image |
129 | --------------------------- | 105 | --------------------------- |
130 | 106 | ||
@@ -149,8 +125,7 @@ In either case, the following conditions must be met: | |||
149 | - CPU register settings | 125 | - CPU register settings |
150 | r0 = 0, | 126 | r0 = 0, |
151 | r1 = machine type number discovered in (3) above. | 127 | r1 = machine type number discovered in (3) above. |
152 | r2 = physical address of tagged list in system RAM, or | 128 | r2 = physical address of tagged list in system RAM. |
153 | physical address of device tree block (dtb) in system RAM | ||
154 | 129 | ||
155 | - CPU mode | 130 | - CPU mode |
156 | All forms of interrupts must be disabled (IRQs and FIQs) | 131 | All forms of interrupts must be disabled (IRQs and FIQs) |