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ARM: zImage: allow supplementing appended DTB with traditional ATAG data

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Some old bootloaders can't be updated to a device tree capable one,
yet they provide ATAGs with memory configuration, the ramdisk address,
the kernel cmdline string, etc.  To allow a device tree enabled
kernel to be used with such bootloaders, it is necessary to convert those
ATAGs into FDT properties and fold them into the DTB appended to zImage.

Currently the following ATAGs are converted:

	ATAG_CMDLINE
	ATAG_MEM
	ATAG_INITRD2

If the corresponding information already exists in the appended DTB, it
is replaced, otherwise the required node is created to hold it.

The code looks for ATAGs at the location pointed by the value of r2 upon
entry into the zImage code.  If no ATAGs are found there, an attempt at
finding ATAGs at the typical 0x100 offset from start of RAM is made.
Otherwise the DTB is left unchanged.

Thisstarted from an older patch from John Bonesio <bones@secretlab.ca>,
with contributions from David Brown <davidb@codeaurora.org>.

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Tested-by: Dave Martin <dave.martin@linaro.org>
Tested-by: Thomas Abraham <thomas.abraham@linaro.org>
This commit is contained in:
Nicolas Pitre
2011-09-13 22:37:07 -04:00
committed by Nicolas Pitre
parent df4879fa26
commit b90b9a3825
6 changed files with 184 additions and 2 deletions
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32
arch/arm/boot/compressed/head.S
View File

@@ -246,6 +246,38 @@ restart: adr r0, LC0
cmp lr, r1
bne dtb_check_done @ not found
#ifdef CONFIG_ARM_ATAG_DTB_COMPAT
/*
* OK... Let's do some funky business here.
* If we do have a DTB appended to zImage, and we do have
* an ATAG list around, we want the later to be translated
* and folded into the former here. To be on the safe side,
* let's temporarily move the stack away into the malloc
* area. No GOT fixup has occurred yet, but none of the
* code we're about to call uses any global variable.
*/
add sp, sp, #0x10000
stmfd sp!, {r0-r3, ip, lr}
mov r0, r8
mov r1, r6
sub r2, sp, r6
bl atags_to_fdt
/*
* If returned value is 1, there is no ATAG at the location
* pointed by r8. Try the typical 0x100 offset from start
* of RAM and hope for the best.
*/
cmp r0, #1
sub r0, r4, #(TEXT_OFFSET - 0x100)
mov r1, r6
sub r2, sp, r6
blne atags_to_fdt
ldmfd sp!, {r0-r3, ip, lr}
sub sp, sp, #0x10000
#endif
mov r8, r6 @ use the appended device tree
/*