arm64: add cpu_is_bsp() concept

It's helpful to know if the current running CPU
is the BSP. Therefore, provide that semantic.

BUG=chrome-os-partner:32082
BRANCH=None
TEST=Built and booted to kernel.

Change-Id: I18cb8ab5149c3337e22b1f6046b1af266be7e47c
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: b390dc70b658c207cd3b64408713ec4cddab3172
Original-Change-Id: I3d5518d1f6d6a78b14f25bb7ef79727605064561
Original-Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/218653
Original-Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: http://review.coreboot.org/9083
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/arch/arm64/c_entry.c

@@ -56,6 +56,7 @@ static void seed_stack(void)
 
 void arm64_init(void)
 {
+	cpu_set_bsp();
 	seed_stack();
 	arm64_soc_init();
 	main();

src/arch/arm64/cpu.c

@@ -27,6 +27,7 @@
 #include "cpu-internal.h"
 
 static struct cpu_info cpu_infos[CONFIG_MAX_CPUS];
+struct cpu_info *bsp_cpu_info;
 
 static inline struct cpu_info *cpu_info_for_cpu(unsigned int id)
 {

src/arch/arm64/include/armv8/arch/cpu.h

@@ -66,6 +66,19 @@ struct cpu_info {
 /* Obtain cpu_info for current executing CPU. */
 struct cpu_info *cpu_info(void);
 
+extern struct cpu_info *bsp_cpu_info;
+
+/* Ran only by BSP at initial boot strapping. */
+static inline void cpu_set_bsp(void)
+{
+	bsp_cpu_info = cpu_info();
+}
+
+static inline int cpu_is_bsp(void)
+{
+	return cpu_info() == bsp_cpu_info;
+}
+
 /* Control routines for starting CPUs. */
 struct cpu_control_ops {
 	/* Return the maximum number of CPUs supported. */