[PATCH] ARM: rcar-gen2: Do not attempt to re-setup timer if running correctly

[Ben Dooks]

If the system has been started in non-secure mode, then the ARM generic
timer is not configurable during the kernel initialisation. Currently
the only thing we can check for is if the timer has been correctly
configured during the boot process.

Signed-off-by: Ben Dooks <ben.dooks at codethink.co.uk>
Reviewed-by: Ian Molton <ian.molton at codethink.co.uk>
---
 arch/arm/mach-shmobile/setup-rcar-gen2.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/arm/mach-shmobile/setup-rcar-gen2.c b/arch/arm/mach-shmobile/setup-rcar-gen2.c
index 5734c24..6b7b7f1 100644
--- a/arch/arm/mach-shmobile/setup-rcar-gen2.c
+++ b/arch/arm/mach-shmobile/setup-rcar-gen2.c
@@ -78,12 +78,20 @@ void __init rcar_gen2_timer_init(void)
 	/* Remap "armgcnt address map" space */
 	base = ioremap(0xe6080000, PAGE_SIZE);
 
-	/* Update registers with correct frequency */
-	iowrite32(freq, base + CNTFID0);
-	asm volatile("mcr p15, 0, %0, c14, c0, 0" : : "r" (freq));
+	/* Update the timer if it is either not running, or is not at the
+	 * right frequency. The timer is only configurable in secure mode
+	 * so this avoids an abort if the loader started the timer and
+	 * started the kernel in non-secure mode. */
+	if ((ioread32(base + CNTCR) & 1) == 0 ||
+	    ioread32(base + CNTFID0) != freq) {
+		/* Update registers with correct frequency */
+		iowrite32(freq, base + CNTFID0);
+		asm volatile("mcr p15, 0, %0, c14, c0, 0" : : "r" (freq));
+
+		/* make sure arch timer is started by setting bit 0 of CNTCR */
+		iowrite32(1, base + CNTCR);
+	}
 
-	/* make sure arch timer is started by setting bit 0 of CNTCR */
-	iowrite32(1, base + CNTCR);
 	iounmap(base);
 #endif /* CONFIG_ARM_ARCH_TIMER */
 
-- 
1.8.5.1