Commit 091994cf authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'spi/merge' of git://git.secretlab.ca/git/linux-2.6 

* 'spi/merge' of git://git.secretlab.ca/git/linux-2.6:
  devicetree-discuss is moderated for non-subscribers
  MAINTAINERS: Add entry for GPIO subsystem
  dt: add documentation of ARM dt boot interface
  dt: Remove obsolete description of powerpc boot interface
  dt: Move device tree documentation out of powerpc directory
  spi/spi_sh_msiof: fix wrong address calculation, which leads to an Oops
parents d8ed516f c170093d

Documentation/arm/Booting

+29 −4
Original line number Diff line number Diff line
@@ -65,13 +65,19 @@ 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 the kernel tagged list

-------------------------------

4. Setup boot data

------------------



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
@@ -101,6 +107,24 @@ 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

---------------------------
@@ -125,7 +149,8 @@ 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.

  r2 = physical address of tagged list in system RAM, or

       physical address of device tree block (dtb) in system RAM



- CPU mode

  All forms of interrupts must be disabled (IRQs and FIQs)

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