v3.10 - big endian core support

Vijay Kilari vijay.kilari at gmail.com
Fri Jul 12 07:56:59 EDT 2013

On Fri, Jul 12, 2013 at 5:17 PM, Thomas Petazzoni
<thomas.petazzoni at free-electrons.com> wrote:
> Dear Vijay Kilari,
> On Fri, 12 Jul 2013 17:09:12 +0530, Vijay Kilari wrote:
>> > Ben Dooks has a separate branch on top of this base branch for
>> > big-endian support, that adds atags compat code to convert the ATAGs
>> > data from LE to BE. See the baserock/311/be/atags branch in
>> > git://git.baserock.org/delta/linux. Or
>> > http://git.baserock.org/cgi-bin/cgit.cgi/delta/linux.git/log/?h=baserock/311/be/atags.
>>  ARM VE TC2 board, enabling CONFIG_THUMB2_KERNEL failed to boot in BE mode
>> It hangs at very early stage of boot
> Yeah, the Thumb2 code is not supported by Ben Dooks patches, it's part
> of the TODO-list. I think Ben said he would probably not have much time
> to work on this. I might be able to spare some time on this, so just
> let me know if I should start working on this. If I remember correctly,
> it's mainly the fixup_pv_table code that needed some Thumb2/BE love.

In fact, I tried with below changes.. still it fails

diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index 2de1114..7df64c7 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -592,8 +592,14 @@ __fixup_a_pv_table:
        b       2f
 1:     add     r7, r3
        ldrh    ip, [r7, #2]
+       rev     ip, ip
        and     ip, 0x8f00
        orr     ip, r6  @ mask in offset bits 31-24
+       rev     ip, ip
        strh    ip, [r7, #2]
 2:     cmp     r4, r5
        ldrcc   r7, [r4], #4    @ use branch for delay slot

> Will, is getting Thumb2 working a requirement to get the BE support
> merged, or can we for now make the BE option depends on !THUMB2_KERNEL ?
> Thanks!
> Thomas
> --
> Thomas Petazzoni, Free Electrons
> Kernel, drivers, real-time and embedded Linux
> development, consulting, training and support.
> http://free-electrons.com

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