armv8: Add Secure Monitor/Hypervisor Call (SMC/HVC) infrastructure

This commit adds functions issuing calls to secure monitor or
hypervisore. This allows using services such as Power State
Coordination Interface (PSCI) provided by firmware, e.g. ARM
Trusted Firmware (ATF)

The SMC call can destroy all registers declared temporary by the
calling conventions. The clobber list is "x0..x17" because of
this

Signed-off-by: Sergey Temerkhanov <s.temerkhanov@gmail.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Radha Mohan Chintakuntla <rchintakuntla@cavium.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Mateusz Kulikowski <mateusz.kulikowski@gmail.com>
diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h
index 393e7af..67cbbc2 100644
--- a/arch/arm/include/asm/system.h
+++ b/arch/arm/include/asm/system.h
@@ -1,6 +1,9 @@
 #ifndef __ASM_ARM_SYSTEM_H
 #define __ASM_ARM_SYSTEM_H
 
+#include <common.h>
+#include <linux/compiler.h>
+
 #ifdef CONFIG_ARM64
 
 /*
@@ -105,6 +108,24 @@
 
 void flush_l3_cache(void);
 
+/*
+ *Issue a hypervisor call in accordance with ARM "SMC Calling convention",
+ * DEN0028A
+ *
+ * @args: input and output arguments
+ *
+ */
+void hvc_call(struct pt_regs *args);
+
+/*
+ *Issue a secure monitor call in accordance with ARM "SMC Calling convention",
+ * DEN0028A
+ *
+ * @args: input and output arguments
+ *
+ */
+void smc_call(struct pt_regs *args);
+
 #endif	/* __ASSEMBLY__ */
 
 #else /* CONFIG_ARM64 */