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Diffstat (limited to 'Documentation/devicetree/booting-without-of.txt')
| -rw-r--r-- | Documentation/devicetree/booting-without-of.txt | 58 |
1 files changed, 19 insertions, 39 deletions
diff --git a/Documentation/devicetree/booting-without-of.txt b/Documentation/devicetree/booting-without-of.txt index 9381a1481027..55fd2623445b 100644 --- a/Documentation/devicetree/booting-without-of.txt +++ b/Documentation/devicetree/booting-without-of.txt @@ -13,7 +13,7 @@ Table of Contents I - Introduction 1) Entry point for arch/powerpc - 2) Entry point for arch/arm + 2) Entry point for arch/x86 II - The DT block format 1) Header @@ -226,45 +226,25 @@ 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). +2) Entry point for arch/x86 +------------------------------- + There is one single 32bit entry point to the kernel at code32_start, + the decompressor (the real mode entry point goes to the same 32bit + entry point once it switched into protected mode). That entry point + supports one calling convention which is documented in + Documentation/x86/boot.txt + The physical pointer to the device-tree block (defined in chapter II) + is passed via setup_data which requires at least boot protocol 2.09. + The type filed is defined as + + #define SETUP_DTB 2 + + This device-tree is used as an extension to the "boot page". As such it + does not parse / consider data which is already covered by the boot + page. This includes memory size, reserved ranges, command line arguments + or initrd address. It simply holds information which can not be retrieved + otherwise like interrupt routing or a list of devices behind an I2C bus. II - The DT block format ======================== |