path: root/Documentation/devicetree/booting-without-of.txt
diff options
authorSebastian Andrzej Siewior <bigeasy@linutronix.de>2011-02-22 21:07:37 +0100
committerThomas Gleixner <tglx@linutronix.de>2011-02-23 22:27:52 +0100
commitda6b737b9ab768dd06bb4b0395131d10e524cf83 (patch)
tree5ae44f22f3be802f2a9d3c09fd068f394efbd0a6 /Documentation/devicetree/booting-without-of.txt
parentf1c2b357148ec27fcc6ce0992211209a0ea20d8f (diff)
x86: Add device tree support
This patch adds minimal support for device tree on x86. The device tree blob is passed to the kernel via setup_data which requires at least boot protocol 2.09. Memory size, restricted memory regions, boot arguments are gathered the traditional way so things like cmd_line are just here to let the code compile. The current plan is use the device tree as an extension and to gather information which can not be enumerated and would have to be hardcoded otherwise. This includes things like - which devices are on this I2C/SPI bus? - how are the interrupts wired to IO APIC? - where could my hpet be? Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Dirk Brandewie <dirk.brandewie@gmail.com> Acked-by: Grant Likely <grant.likely@secretlab.ca> Cc: sodaville@linutronix.de Cc: devicetree-discuss@lists.ozlabs.org LKML-Reference: <1298405266-1624-3-git-send-email-bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'Documentation/devicetree/booting-without-of.txt')
1 files changed, 20 insertions, 0 deletions
diff --git a/Documentation/devicetree/booting-without-of.txt b/Documentation/devicetree/booting-without-of.txt
index 28b1c9d3d351..55fd2623445b 100644
--- a/Documentation/devicetree/booting-without-of.txt
+++ b/Documentation/devicetree/booting-without-of.txt
@@ -13,6 +13,7 @@ Table of Contents
I - Introduction
1) Entry point for arch/powerpc
+ 2) Entry point for arch/x86
II - The DT block format
1) Header
@@ -225,6 +226,25 @@ it with special cases.
cannot support both configurations with Book E and configurations
with classic Powerpc architectures.
+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