[U-Boot] [PATCH 4/9] ARM: non-sec: reset CNTVOFF to zero

[Andre Przywara]

On 11/21/2013 09:59 AM, Marc Zyngier wrote:
> Before switching to non-secure, make sure that CNTVOFF is set
> to zero on all CPUs. Otherwise, kernel running in non-secure
> without HYP enabled (hence using virtual timers) may observe
> timers that are not synchronized, effectively seeing time
> going backward...

Under what circumstances would native Linux use the virtual timers? When 
VIRT_EXT is not defined?

Regards,
Andre.

>
> Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
> ---
>   arch/arm/cpu/armv7/nonsec_virt.S | 7 +++++++
>   1 file changed, 7 insertions(+)
>
> diff --git a/arch/arm/cpu/armv7/nonsec_virt.S b/arch/arm/cpu/armv7/nonsec_virt.S
> index 648066f..bbacbce 100644
> --- a/arch/arm/cpu/armv7/nonsec_virt.S
> +++ b/arch/arm/cpu/armv7/nonsec_virt.S
> @@ -53,7 +53,14 @@ _secure_monitor:
>   	mrceq	p15, 0, r0, c12, c0, 1		@ get MVBAR value
>   	mcreq	p15, 4, r0, c12, c0, 0		@ write HVBAR
>   #endif
> +	bne	1f
>
> +	@ Reset CNTVOFF to 0 before leaving monitor mode
> +	mrc	p15, 0, r0, c0, c1, 1		@ read ID_PFR1
> +	ands	r0, r0, #CPUID_ARM_GENTIMER_MASK	@ test arch timer bits
> +	movne	r0, #0
> +	mcrrne	p15, 4, r0, r0, c14		@ Reset CNTVOFF to zero
> +1:
>   	movs	pc, lr				@ return to non-secure SVC
>
>   _hyp_trap:
>