diff options
| -rw-r--r-- | Documentation/arm/Booting | 33 | ||||
| -rw-r--r-- | Documentation/devicetree/booting-without-of.txt | 40 |
2 files changed, 4 insertions, 69 deletions
diff --git a/Documentation/arm/Booting b/Documentation/arm/Booting index 4e686a2ed91..76850295af8 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) |
diff --git a/Documentation/devicetree/booting-without-of.txt b/Documentation/devicetree/booting-without-of.txt index 9381a148102..28b1c9d3d35 100644 --- a/Documentation/devicetree/booting-without-of.txt +++ b/Documentation/devicetree/booting-without-of.txt | |||
| @@ -13,7 +13,6 @@ Table of Contents | |||
| 13 | 13 | ||
| 14 | I - Introduction | 14 | I - Introduction |
| 15 | 1) Entry point for arch/powerpc | 15 | 1) Entry point for arch/powerpc |
| 16 | 2) Entry point for arch/arm | ||
| 17 | 16 | ||
| 18 | II - The DT block format | 17 | II - The DT block format |
| 19 | 1) Header | 18 | 1) Header |
| @@ -226,45 +225,6 @@ it with special cases. | |||
| 226 | cannot support both configurations with Book E and configurations | 225 | cannot support both configurations with Book E and configurations |
| 227 | with classic Powerpc architectures. | 226 | with classic Powerpc architectures. |
| 228 | 227 | ||
| 229 | 2) Entry point for arch/arm | ||
| 230 | --------------------------- | ||
| 231 | |||
| 232 | There is one single entry point to the kernel, at the start | ||
| 233 | of the kernel image. That entry point supports two calling | ||
| 234 | conventions. A summary of the interface is described here. A full | ||
| 235 | description of the boot requirements is documented in | ||
| 236 | Documentation/arm/Booting | ||
| 237 | |||
| 238 | a) ATAGS interface. Minimal information is passed from firmware | ||
| 239 | to the kernel with a tagged list of predefined parameters. | ||
| 240 | |||
| 241 | r0 : 0 | ||
| 242 | |||
| 243 | r1 : Machine type number | ||
| 244 | |||
| 245 | r2 : Physical address of tagged list in system RAM | ||
| 246 | |||
| 247 | b) Entry with a flattened device-tree block. Firmware loads the | ||
| 248 | physical address of the flattened device tree block (dtb) into r2, | ||
| 249 | r1 is not used, but it is considered good practise to use a valid | ||
| 250 | machine number as described in Documentation/arm/Booting. | ||
| 251 | |||
| 252 | r0 : 0 | ||
| 253 | |||
| 254 | r1 : Valid machine type number. When using a device tree, | ||
| 255 | a single machine type number will often be assigned to | ||
| 256 | represent a class or family of SoCs. | ||
| 257 | |||
| 258 | r2 : physical pointer to the device-tree block | ||
| 259 | (defined in chapter II) in RAM. Device tree can be located | ||
| 260 | anywhere in system RAM, but it should be aligned on a 32 bit | ||
| 261 | boundary. | ||
| 262 | |||
| 263 | The kernel will differentiate between ATAGS and device tree booting by | ||
| 264 | reading the memory pointed to by r1 and looking for either the flattened | ||
| 265 | device tree block magic value (0xd00dfeed) or the ATAG_CORE value at | ||
| 266 | offset 0x4 from r2 (0x54410001). | ||
| 267 | |||
| 268 | 228 | ||
| 269 | II - The DT block format | 229 | II - The DT block format |
| 270 | ======================== | 230 | ======================== |
