Subject: [PATCH 04/14] ARM: set BE8 if LE in head code

From: [email-masked] (Ben Dooks)
Date: Wed, 24 Jul 2013 16:55:05 +0100

On 24/07/13 15:41, Will Deacon wrote:
> On Wed, Jul 24, 2013 at 11:27:52AM +0100, Ben Dooks wrote:
>> If we are booting in LE and compiled for BE8, then add code to
>> set the state to bE8. Since the instruction stream is always LE,
>> we do not need to do anything special to the instruction.
>>
>> Also ensure that the secondary processors are started in the same mode.
>>
>> Note, we do add about 20 bytes to the kernel image, but it seems easier
>> to do this than adding another configuration to change.
>>
>> Signed-off-by: Ben Dooks<[email-masked]>
>> ---
>>   arch/arm/boot/compressed/head.S |    1 +
>>   arch/arm/kernel/head.S          |    4 ++++
>>   arch/arm/kernel/sleep.S         |    1 +
>>   3 files changed, 6 insertions(+)
>>
>> diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
>> index 4eb8364..4d83bfd 100644
>> --- a/arch/arm/boot/compressed/head.S
>> +++ b/arch/arm/boot/compressed/head.S
>> @@ -135,6 +135,7 @@ start:
>>   		.word	_edata			@ zImage end address
>>    THUMB(		.thumb			)
>>   1:
>> + ARM_BE8(	setend	be )			@ go BE8 if LE, no-op if BE8
 >
> I find the comment here slightly confusing as it makes it sound like the
> macro expands to nothing if we're BE8 (which is clearly not the case).

I've changed it to "go BE8 if compiled for BE8"

>>   		mrs	r9, cpsr
>>   #ifdef CONFIG_ARM_VIRT_EXT
>>   		bl	__hyp_stub_install	@ get into SVC mode, reversibly
>> diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
>> index e40c0b3b..706c441 100644
>> --- a/arch/arm/kernel/head.S
>> +++ b/arch/arm/kernel/head.S
>> @@ -77,6 +77,7 @@
>>
>>   	__HEAD
>>   ENTRY(stext)
>> + ARM_BE8(setend	be )			@ ensure we are in BE8 mode
>
> Alignment issue here -- please try to align the instruction with the
> instructions below (it's awkward to read with all the brackets).

If I move it one to the left, then it gets coloured blue by
my editor, as it is the first thing on the line like the
ENTRY() macro.

>>
>>    THUMB(	adr	r9, BSYM(1f)	)	@ Kernel is always entered in ARM.
>>    THUMB(	bx	r9		)	@ If this is a Thumb-2 kernel,
>> @@ -351,6 +352,9 @@ ENTRY(secondary_startup)
>>   	 * the processor type - there is no need to check the machine type
>>   	 * as it has already been validated by the primary processor.
>>   	 */
>> +
>> + ARM_BE8(setend	be)				@ if system starts LE, go BE8
>> +
>>   #ifdef CONFIG_ARM_VIRT_EXT
>>   	bl	__hyp_stub_install_secondary
>>   #endif
>> diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S
>> index 987dcf3..954c28a 100644
>> --- a/arch/arm/kernel/sleep.S
>> +++ b/arch/arm/kernel/sleep.S
>> @@ -81,6 +81,7 @@ ENDPROC(cpu_resume_after_mmu)
>>   	.data
>>   	.align
>>   ENTRY(cpu_resume)
>> +ARM_BE8(setend be)			@ ensure we are in BE mode
>
> Any reason to have three different comments for the same thing? I think you
> probably just need to comment the one in head.S.

I've changed the comments to match in.

-- 
Ben Dooks				http://www.codethink.co.uk/
Senior Engineer				Codethink - Providing Genius