stage_cache: Add resume_from_stage_cache()

Factor out the condition when an attempt to load
stage from cache can be tried.

Change-Id: I936f07bed6fc82f46118d217f1fd233e2e041405
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50000
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/include/stage_cache.h

@@ -3,6 +3,7 @@
 #ifndef _STAGE_CACHE_H_
 #define _STAGE_CACHE_H_
 
+#include <romstage_handoff.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <program_loading.h>
@@ -38,6 +39,15 @@ static inline void stage_cache_get_raw(int stage_id, void **base, size_t *size)
 
 #endif
 
+static inline int resume_from_stage_cache(void)
+{
+	if (CONFIG(NO_STAGE_CACHE))
+		return 0;
+
+	/* TBD: Replace this with acpi_is_wakeup_s3(). */
+	return romstage_handoff_is_resume();
+}
+
 /* Fill in parameters for the external stage cache, if utilized. */
 void stage_cache_external_region(void **base, size_t *size);