diff options
authorGrant Likely <>2011-02-14 08:13:20 -0700
committerGrant Likely <>2011-02-14 08:13:20 -0700
commit7211da17785536bacd3171a28bc6a3853c8bb477 (patch)
parent9830fcd6f6a4781d8b46d2b35c13b39f30915c63 (diff)
Revert "dt: add documentation of ARM dt boot interface"
This reverts commit 9830fcd6f6a4781d8b46d2b35c13b39f30915c63. The ARM dt support has not been merged yet; this documentation update was premature. Signed-off-by: Grant Likely <>
2 files changed, 4 insertions, 69 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.
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
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 9381a1481027..28b1c9d3d351 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