From 318c1fce4aeef298cbb6153416c499c94ad7cda0 Mon Sep 17 00:00:00 2001 From: Jonas Gorski Date: Tue, 24 Jun 2014 10:53:15 +0200 Subject: [PATCH RFC v3] MIPS: add support for vmlinux.bin appended DTB Add support for populating initial_boot_params through a dtb blob appended to raw vmlinux.bin. Signed-off-by: Jonas Gorski --- Changes RFC v2 -> v3 * fixed !smp kernels (TODO: move it to its own patch Changes RFC v1 -> v2 * changed all occurences of vmlinux to vmlinux.bin * clarified this applies to the raw vmlinux.bin without decompressor * s/initial_device_params/initial_boot_params/ Initial comments by me still valid: Mostly adapted from how ARM is doing it. Sent as an RFC PATCH because I am not sure if this is the right way to it, and whether storing the pointer in initial_boot_params is a good idea, or a new variable should be introduced. The reasoning for initial_boot_params is that there is no common MIPS interface yet, so the next best thing was using that. This also has the advantage of keeping the original fw_args intact. This patch works for me on bcm63xx, where the bootloader expects an lzma compressed kernel, so I didn't want to double compress using the in-kernel compressed kernel support. Completely untested on anything except MIPS32 / big endian. arch/mips/Kconfig | 18 ++++++++++++++++++ arch/mips/kernel/head.S | 19 +++++++++++++++++++ arch/mips/kernel/vmlinux.lds.S | 7 +++++++ 3 files changed, 43 insertions(+) --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -2645,6 +2645,24 @@ config RAPIDIO source "drivers/rapidio/Kconfig" +config MIPS_APPENDED_DTB + bool "Use appended device tree blob to vmlinux.bin (EXPERIMENTAL)" + depends on OF + help + With this option, the boot code will look for a device tree binary + DTB) appended to raw vmlinux.bin (without decompressor). + (e.g. cat vmlinux.bin .dtb > vmlinux_w_dtb). + + This is meant as a backward compatibility convenience for those + systems with a bootloader that can't be upgraded to accommodate + the documented boot protocol using a device tree. + + Beware that there is very little in terms of protection against + this option being confused by leftover garbage in memory that might + look like a DTB header after a reboot if no actual DTB is appended + to vmlinux.bin. Do not leave this option active in a production kernel + if you don't intend to always append a DTB. + endmenu menu "Executable file formats" --- a/arch/mips/kernel/head.S +++ b/arch/mips/kernel/head.S @@ -100,6 +100,22 @@ NESTED(kernel_entry, 16, sp) # kernel jr t0 0: +#ifdef CONFIG_MIPS_APPENDED_DTB + PTR_LA t0, __appended_dtb + PTR_LI t3, 0 + +#ifdef CONFIG_CPU_BIG_ENDIAN + PTR_LI t1, 0xd00dfeed +#else + PTR_LI t1, 0xedfe0dd0 +#endif + LONG_L t2, (t0) + bne t1, t2, not_found + + PTR_LA t3, __appended_dtb + +not_found: +#endif PTR_LA t0, __bss_start # clear .bss LONG_S zero, (t0) PTR_LA t1, __bss_stop - LONGSIZE @@ -113,6 +129,10 @@ NESTED(kernel_entry, 16, sp) # kernel LONG_S a2, fw_arg2 LONG_S a3, fw_arg3 +#ifdef CONFIG_MIPS_APPENDED_DTB + LONG_S t3, initial_boot_params +#endif + MTC0 zero, CP0_CONTEXT # clear context register PTR_LA $28, init_thread_union /* Set the SP after an empty pt_regs. */ --- a/arch/mips/kernel/vmlinux.lds.S +++ b/arch/mips/kernel/vmlinux.lds.S @@ -125,8 +125,14 @@ SECTIONS .exit.data : { EXIT_DATA } - +#ifdef CONFIG_SMP PERCPU_SECTION(1 << CONFIG_MIPS_L1_CACHE_SHIFT) +#endif +#ifdef CONFIG_MIPS_APPENDED_DTB + __appended_dtb = .; + /* leave space for appended DTB */ + . = . + 0x100000; +#endif /* * Align to 64K in attempt to eliminate holes before the * .bss..swapper_pg_dir section at the start of .bss. This