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

[Marc Zyngier]

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...

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:
-- 
1.8.2.3