Subject: [PATCH] ARM: socfpga: put back v7_invalidate_l1 in socfpga_secondary_startup

From: [email-masked] (Jisheng Zhang)
Date: Thu, 9 Jul 2015 11:52:49 +0800

Dear Russell,

On Wed, 8 Jul 2015 22:07:34 +0100
Russell King - ARM Linux <[email-masked]> wrote:

> On Wed, Jul 08, 2015 at 02:13:32PM -0500, Dinh Nguyen wrote:
> > The value of CPACR is 0x00F00000. So cp11 and cp10 are privileged and
> > user mode access.
> 
> Hmm.
> 
> I think what you've found is a(nother) latent bug in the CPU bring up
> code.
> 
> For SMP CPUs, the sequence we're following during early initialisation is:
> 
> 1. Enable SMP coherency.
> 2. Invalidate the caches.
> 
> If the cache contains rubbish, enabling SMP coherency before invalidating
> the cache is plainly an absurd thing to do.
> 
> Can you try the patch below - not tested in any way, so you may need to
> tweak it, but it should allow us to prove that point.
> 
> diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
> index 0716bbe19872..db5137fc297d 100644
> --- a/arch/arm/mm/proc-v7.S
> +++ b/arch/arm/mm/proc-v7.S
> @@ -275,6 +275,10 @@ __v7_b15mp_setup:
>  __v7_ca17mp_setup:
>  	mov	r10, #0
>  1:
> +	adr	r12, __v7_setup_stack		@ the local stack
> +	stmia	r12, {r0-r5, r7, r9-r11, lr}
> +	bl      v7_invalidate_l1
> +	ldmia	r12, {r0-r5, r7, r9-r11, lr}

Some CPUs such as CA7 need enable SMP before any cache maintenance.

CA7 TRM says something about SMP bit:
"You must ensure this bit is set to 1 before the caches and MMU are enabled,
or any cache and TLB maintenance operations are performed."

So it seems we need to use different path for different CPUs.

Also CA7 would invalidate L1 automatically once reset, can we remove the
invalidate op in CA7 case?

I'm not sure I understand the code correctly, criticism is welcome.

Thanks,
Jisheng

>  #ifdef CONFIG_SMP
>  	ALT_SMP(mrc	p15, 0, r0, c1, c0, 1)
>  	ALT_UP(mov	r0, #(1 << 6))		@ fake it for UP
> @@ -283,7 +287,7 @@ __v7_ca17mp_setup:
>  	orreq	r0, r0, r10			@ Enable CPU-specific SMP bits
>  	mcreq	p15, 0, r0, c1, c0, 1
>  #endif
> -	b	__v7_setup
> +	b	__v7_setup_cont
>  
>  /*
>   * Errata:
> @@ -417,6 +421,7 @@ __v7_setup:
>  	bl      v7_invalidate_l1
>  	ldmia	r12, {r0-r5, r7, r9, r11, lr}
>  
> +__v7_setup_cont:
>  	and	r0, r9, #0xff000000		@ ARM?
>  	teq	r0, #0x41000000
>  	bne	__errata_finish
> @@ -480,7 +485,7 @@ ENDPROC(__v7_setup)
>  
>  	.align	2
>  __v7_setup_stack:
> -	.space	4 * 11				@ 11 registers
> +	.space	4 * 12				@ 12 registers
>  
>  	__INITDATA
>