From 9c24ce29b2b8c60d4bcca90c0a4da54b28f0b4e7 Mon Sep 17 00:00:00 2001 From: Kevin Cernekee Date: Thu, 25 Dec 2014 09:49:11 -0800 Subject: [PATCH] MIPS: BMIPS: Document the firmware->kernel DTB interface Add a new section covering the Generic BMIPS machine type. Signed-off-by: Kevin Cernekee 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: Ralf Baechle --- .../devicetree/booting-without-of.txt | 28 +++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/Documentation/devicetree/booting-without-of.txt b/Documentation/devicetree/booting-without-of.txt index 77685185cf3b..e49e423268c0 100644 --- a/Documentation/devicetree/booting-without-of.txt +++ b/Documentation/devicetree/booting-without-of.txt @@ -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 ======================== -- 2.20.1