For bootloaders that support booting only ELF kernels and load only ELF
segments to memory there is no easy way to supply DTB without kernel
recompilation. For that purpose, create a section called .appended_dtb
that can be later updated with board-specific DTB using binutils e.g. at
kernel installation time.
Signed-off-by: Aaro Koskinen <aaro.koskinen@xxxxxxxxx>
---
arch/mips/Kconfig | 14 ++++++++++++++
arch/mips/kernel/setup.c | 4 ++++
arch/mips/kernel/vmlinux.lds.S | 5 +++++
3 files changed, 23 insertions(+)
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 199a835..f22ff1b 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -2686,6 +2686,20 @@ choice
help
Do not enable appended dtb support.
+ config MIPS_ELF_APPENDED_DTB
+ bool "vmlinux"
+ help
+ With this option, the boot code will look for a device tree binary
+ DTB) included in the vmlinux ELF section .appended_dtb. By default
+ it is empty and the DTB can be appended using binutils command
+ objcopy:
+
+ objcopy --update-section .appended_dtb=<filename>.dtb vmlinux
+
+ This is meant as a backward compatiblity convenience for those
+ systems with a bootloader that can't be upgraded to accommodate
+ the documented boot protocol using a device tree.
+
config MIPS_RAW_APPENDED_DTB
bool "vmlinux.bin"
help
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 008b337..fb022f4 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -38,6 +38,10 @@
#include <asm/smp-ops.h>
#include <asm/prom.h>
+#ifdef CONFIG_MIPS_ELF_APPENDED_DTB
+const char __section(.appended_dtb) __appended_dtb[0x100000];
+#endif /* CONFIG_MIPS_ELF_APPENDED_DTB */
+
struct cpuinfo_mips cpu_data[NR_CPUS] __read_mostly;
EXPORT_SYMBOL(cpu_data);
diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
index 07d32a4..f4c23d9 100644
--- a/arch/mips/kernel/vmlinux.lds.S
+++ b/arch/mips/kernel/vmlinux.lds.S
@@ -132,6 +132,11 @@ SECTIONS
__appended_dtb = .;
/* leave space for appended DTB */
. += 0x100000;
+#elif defined(CONFIG_MIPS_ELF_APPENDED_DTB)
+ .appended_dtb : AT(ADDR(.appended_dtb) - LOAD_OFFSET) {
+ *(.appended_dtb)
+ KEEP(*(.appended_dtb))
+ }
#endif
/*
* Align to 64K in attempt to eliminate holes before the
--
2.4.3
