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Commit 9c24ce29 authored by Kevin Cernekee's avatar Kevin Cernekee Committed by Ralf Baechle
Browse files

MIPS: BMIPS: Document the firmware->kernel DTB interface 



Add a new section covering the Generic BMIPS machine type.

Signed-off-by: default avatarKevin Cernekee <cernekee@gmail.com>
Cc: f.fainelli@gmail.com
Cc: jaedon.shin@gmail.com
Cc: abrestic@chromium.org
Cc: tglx@linutronix.de
Cc: jason@lakedaemon.net
Cc: jogo@openwrt.org
Cc: arnd@arndb.de
Cc: computersforpeace@gmail.com
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/8849/


Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
parent 5432eeb6

Documentation/devicetree/booting-without-of.txt

+28 −0
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ Table of Contents 
    1) Entry point for arch/arm

    2) Entry point for arch/powerpc

    3) Entry point for arch/x86

    4) Entry point for arch/mips/bmips



  II - The DT block format

    1) Header
@@ -288,6 +289,33 @@ it with special cases. 
  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.



4) Entry point for arch/mips/bmips

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



  Some bootloaders only support a single entry point, at the start of the

  kernel image.  Other bootloaders will jump to the ELF start address.

  Both schemes are supported; CONFIG_BOOT_RAW=y and CONFIG_NO_EXCEPT_FILL=y,

  so the first instruction immediately jumps to kernel_entry().



  Similar to the arch/arm case (b), a DT-aware bootloader is expected to

  set up the following registers:



         a0 : 0



         a1 : 0xffffffff



         a2 : Physical pointer to the device tree block (defined in chapter

         II) in RAM.  The device tree can be located anywhere in the first

         512MB of the physical address space (0x00000000 - 0x1fffffff),

         aligned on a 64 bit boundary.



  Legacy bootloaders do not use this convention, and they do not pass in a

  DT block.  In this case, Linux will look for a builtin DTB, selected via

  CONFIG_DT_*.



  This convention is defined for 32-bit systems only, as there are not

  currently any 64-bit BMIPS implementations.



II - The DT block format

========================