[PATCHv2 1/3] ARM: mvebu: make the coherency_ll.S functions work with no coherency fabric

[gregory.clement@free-electrons.com (Gregory CLEMENT)]

Hi Thomas,

On 27/10/2014 16:32, Thomas Petazzoni wrote:
> The ll_add_cpu_to_smp_group(), ll_enable_coherency() and
> ll_disable_coherency() are used on Armada XP to control the coherency
> fabric. However, they make the assumption that the coherency fabric is
> always available, which is currently a correct assumption but will no
> longer be true with a followup commit that disables the usage of the
> coherency fabric when the conditions are not met to use it.
> 
> Therefore, this commit modifies those functions so that they check the
> return value of ll_get_coherency_base(), and if the return value is 0,
> they simply return without configuring anything in the coherency
> fabric.
> 
> The ll_get_coherency_base() function is also modified to properly
> return 0 when the function is called with the MMU disabled. In this
> case, it normally returns the physical address of the coherency
> fabric, but we now check if the virtual address is 0, and if that's
> case, return a physical address of 0 to indicate that the coherency
> fabric is not enabled.
> 
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> Cc: <stable@vger.kernel.org> # v3.8+
> ---
>  arch/arm/mach-mvebu/coherency_ll.S | 21 +++++++++++++++++++--
>  1 file changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/mach-mvebu/coherency_ll.S b/arch/arm/mach-mvebu/coherency_ll.S
> index f5d881b..0ed07c3 100644
> --- a/arch/arm/mach-mvebu/coherency_ll.S
> +++ b/arch/arm/mach-mvebu/coherency_ll.S
> @@ -24,7 +24,10 @@
>  #include <asm/cp15.h>
>  
>  	.text
> -/* Returns the coherency base address in r1 (r0 is untouched) */
> +/*
> + * Returns the coherency base address in r1 (r0 is untouched), or 0 if
> + * the coherency fabric is not enabled.
> + */
>  ENTRY(ll_get_coherency_base)
>  	mrc	p15, 0, r1, c1, c0, 0
>  	tst	r1, #CR_M @ Check MMU bit enabled
> @@ -32,8 +35,13 @@ ENTRY(ll_get_coherency_base)
>  
>  	/*
>  	 * MMU is disabled, use the physical address of the coherency
> -	 * base address.
> +	 * base address. However, if the coherency fabric isn't mapped
> +	 * (i.e its virtual address is zero), it means coherency is
> +	 * not enabled, so we return 0.
>  	 */
> +	ldr	r1, =coherency_base
> +	cmp	r1, #0
> +	beq	2f
>  	adr	r1, 3f
>  	ldr	r3, [r1]
>  	ldr	r1, [r1, r3]
> @@ -85,6 +93,9 @@ ENTRY(ll_add_cpu_to_smp_group)
>  	 */
>  	mov 	r0, lr
>  	bl	ll_get_coherency_base
> +	/* Bail out if the coherency is not enabled */
> +	cmp	r1, #0
> +	moveq	pc, r0

Since the commit "6ebbf2ce437b33022d30badd49dc94d33ecfa498:
ARM: convert all "mov.* pc, reg" to "bx reg" for ARMv6+", you should
use "reteq r0" instead of "moveq	pc, r0".

>  	bl	ll_get_coherency_cpumask
>  	mov 	lr, r0
>  	add	r0, r1, #ARMADA_XP_CFB_CFG_REG_OFFSET
> @@ -107,6 +118,9 @@ ENTRY(ll_enable_coherency)
>  	 */
>  	mov r0, lr
>  	bl	ll_get_coherency_base
> +	/* Bail out if the coherency is not enabled */
> +	cmp	r1, #0
> +	moveq	pc, r0

Same here

>  	bl	ll_get_coherency_cpumask
>  	mov lr, r0
>  	add	r0, r1, #ARMADA_XP_CFB_CTL_REG_OFFSET
> @@ -131,6 +145,9 @@ ENTRY(ll_disable_coherency)
>  	 */
>  	mov 	r0, lr
>  	bl	ll_get_coherency_base
> +	/* Bail out if the coherency is not enabled */
> +	cmp	r1, #0
> +	moveq	pc, r0

and same here

>  	bl	ll_get_coherency_cpumask
>  	mov 	lr, r0
>  	add	r0, r1, #ARMADA_XP_CFB_CTL_REG_OFFSET
> 

Besides this small changes:


Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>


Thanks,

Gregory


-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com