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 4e686a2..7685029 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. The boot loader must ultimately be able to provide a MACH_TYPE_xxx value to the kernel. (see linux/arch/arm/tools/mach-types). -4. Setup boot data ------------------- + +4. Setup the kernel tagged list +------------------------------- Existing boot loaders: OPTIONAL, HIGHLY RECOMMENDED New boot loaders: MANDATORY -The boot loader must provide either a tagged list or a dtb image for -passing configuration data to the kernel. The physical address of the -boot data is passed to the kernel in register r2. - -4a. Setup the kernel tagged list --------------------------------- - The boot loader must create and initialise the kernel tagged list. A valid tagged list starts with ATAG_CORE and ends with ATAG_NONE. 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 the kernel decompressor nor initrd 'bootp' program will overwrite it. The recommended placement is in the first 16KiB of RAM. -4b. Setup the device tree -------------------------- - -The boot loader must load a device tree image (dtb) into system ram -at a 64bit aligned address and initialize it with the boot data. The -dtb format is documented in Documentation/devicetree/booting-without-of.txt. -The kernel will look for the dtb magic value of 0xd00dfeed at the dtb -physical address to determine if a dtb has been passed instead of a -tagged list. - -The boot loader must pass at a minimum the size and location of the -system memory, and the root filesystem location. The dtb must be -placed in a region of memory where the kernel decompressor will not -overwrite it. The recommended placement is in the first 16KiB of RAM -with the caveat that it may not be located at physical address 0 since -the kernel interprets a value of 0 in r2 to mean neither a tagged list -nor a dtb were passed. - 5. Calling the kernel image --------------------------- @@ -149,8 +125,7 @@ In either case, the following conditions must be met: - CPU register settings r0 = 0, r1 = machine type number discovered in (3) above. - r2 = physical address of tagged list in system RAM, or - physical address of device tree block (dtb) in system RAM + r2 = physical address of tagged list in system RAM. - CPU mode 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 9381a14..28b1c9d 100644 --- a/Documentation/devicetree/booting-without-of.txt +++ b/Documentation/devicetree/booting-without-of.txt @@ -13,7 +13,6 @@ Table of Contents I - Introduction 1) Entry point for arch/powerpc - 2) Entry point for arch/arm II - The DT block format 1) Header @@ -226,45 +225,6 @@ it with special cases. cannot support both configurations with Book E and configurations with classic Powerpc architectures. -2) Entry point for arch/arm ---------------------------- - - There is one single entry point to the kernel, at the start - of the kernel image. That entry point supports two calling - conventions. A summary of the interface is described here. A full - description of the boot requirements is documented in - Documentation/arm/Booting - - a) ATAGS interface. Minimal information is passed from firmware - to the kernel with a tagged list of predefined parameters. - - r0 : 0 - - r1 : Machine type number - - r2 : Physical address of tagged list in system RAM - - b) Entry with a flattened device-tree block. Firmware loads the - physical address of the flattened device tree block (dtb) into r2, - r1 is not used, but it is considered good practise to use a valid - machine number as described in Documentation/arm/Booting. - - r0 : 0 - - r1 : Valid machine type number. When using a device tree, - a single machine type number will often be assigned to - represent a class or family of SoCs. - - r2 : physical pointer to the device-tree block - (defined in chapter II) in RAM. Device tree can be located - anywhere in system RAM, but it should be aligned on a 32 bit - boundary. - - The kernel will differentiate between ATAGS and device tree booting by - reading the memory pointed to by r1 and looking for either the flattened - device tree block magic value (0xd00dfeed) or the ATAG_CORE value at - offset 0x4 from r2 (0x54410001). - II - The DT block format ======================== |