Add support for populating initial_device_params through a dtb blob appended to vmlinux. Signed-off-by: Jonas Gorski <jogo@xxxxxxxxxxx> --- 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_device_params is a good idea, or a new variable should be introduced. The reasoning for initial_device_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 bootloade expects an lzma compressed kernel, so I wanted to not 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 | 6 ++++++ 3 files changed, 43 insertions(+) diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig index 3f05b56..58527cd 100644 --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -2476,6 +2476,24 @@ config USE_OF select OF_EARLY_FLATTREE select IRQ_DOMAIN +config MIPS_APPENDED_DTB + bool "Use appended device tree blob to vmlinux (EXPERIMENTAL)" + depends on OF + help + With this option, the boot code will look for a device tree binary + DTB) appended to vmlinux + (e.g. cat vmlinux <filename>.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. Do not leave this option active in a production kernel + if you don't intend to always append a DTB. + endmenu config LOCKDEP_SUPPORT diff --git a/arch/mips/kernel/head.S b/arch/mips/kernel/head.S index 95afd66..72c1049 100644 --- a/arch/mips/kernel/head.S +++ b/arch/mips/kernel/head.S @@ -93,7 +93,22 @@ NESTED(kernel_entry, 16, sp) # kernel entry point PTR_LA t0, 0f 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 @@ -107,6 +122,10 @@ NESTED(kernel_entry, 16, sp) # kernel entry point 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. */ diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S index 3b46f7c..8009530 100644 --- a/arch/mips/kernel/vmlinux.lds.S +++ b/arch/mips/kernel/vmlinux.lds.S @@ -127,6 +127,12 @@ SECTIONS } PERCPU_SECTION(1 << CONFIG_MIPS_L1_CACHE_SHIFT) + +#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 -- 2.0.0
