ARM: vf610: Add ARM Global Timer clocksource option

Add the ARM Global Timer as clocksource/scheduler clock option and
use it as default scheduler clock. This leaves the PIT timer for
other users e.g. the secondary Cortex-M4 core. Also, the Global Timer
has double the precission (running at pheripheral clock compared to
IPG clock) and a 64-bit incrementing counter register. We still keep
the PIT timer as an secondary option in case the ARM Global Timer is
not available.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Acked-by: Bill Pringlemeir <bpringlemeir@nbsps.com>
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>

arch/arm/mach-imx/Kconfig

@@ -633,12 +633,31 @@ config SOC_VF610
 	bool "Vybrid Family VF610 support"
 	select ARM_GIC
 	select PINCTRL_VF610
-	select VF_PIT_TIMER
 	select PL310_ERRATA_769419 if CACHE_L2X0
 
 	help
 	  This enable support for Freescale Vybrid VF610 processor.
 
+choice
+	prompt "Clocksource for scheduler clock"
+	depends on SOC_VF610
+	default VF_USE_ARM_GLOBAL_TIMER
+
+	config VF_USE_ARM_GLOBAL_TIMER
+		bool "Use ARM Global Timer"
+		select ARM_GLOBAL_TIMER
+		select CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
+		help
+		  Use the ARM Global Timer as clocksource
+
+	config VF_USE_PIT_TIMER
+		bool "Use PIT timer"
+		select VF_PIT_TIMER
+		help
+		  Use SoC Periodic Interrupt Timer (PIT) as clocksource
+
+endchoice
+
 endif
 
 source "arch/arm/mach-imx/devices/Kconfig"