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

Will Deacon
2013-07-24T14:41:19Z

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 <ben.dooks@codethink.co.uk>
> ---
> 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).

> 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).

>
> 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.

Will