fsp_baytrail: Get FSP reserved memory from the FSP HOB list

Because the pointer to the FSP HOB list is now being saved, we can
use that to find the top of usable memory.  This eliminates the need
to hardcode the size of the FSP reserved memory area.

Tested on minnowboard max for baytrail.

The HOB structure used does not seem to be present for the rangeley
or ivybridge/pantherpoint FSPs.  At the very least, the GUID is not
documented in the integration guides.

Change-Id: I643e57655f55bfada60075b55aad2ce010ec4f67
Signed-off-by: Martin Roth <gaumless@gmail.com>
Reviewed-on: http://review.coreboot.org/8308
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-by: Aaron Durbin <adurbin@google.com>

src/drivers/intel/fsp/fsp_util.c

@@ -195,6 +195,26 @@ void * find_saved_temp_mem(void *hob_list_ptr)
 	return (void *) ((char *) saved_mem_hob + sizeof(EFI_HOB_GUID_TYPE));
 }
 
+#ifndef FSP_RESERVE_MEMORY_SIZE
+/** @brief locates the HOB containing the location of the fsp reserved mem area
+ *
+ * @param hob_list_ptr pointer to the start of the hob list
+ * @return pointer to the start of the FSP reserved memory or NULL if not found.
+ */
+void * find_fsp_reserved_mem(void *hob_list_ptr)
+{
+	EFI_GUID fsp_reserved_guid = FSP_HOB_RESOURCE_OWNER_FSP_GUID;
+	EFI_HOB_RESOURCE_DESCRIPTOR *fsp_reserved_mem =
+			(EFI_HOB_RESOURCE_DESCRIPTOR *) find_hob_by_guid(
+			hob_list_ptr, &fsp_reserved_guid);
+
+	if (fsp_reserved_mem == NULL)
+		return NULL;
+
+	return  (void *)((uintptr_t)fsp_reserved_mem->PhysicalStart);
+}
+#endif /* FSP_RESERVE_MEMORY_SIZE */
+
 #ifndef __PRE_RAM__ /* Only parse HOB data in ramstage */
 
 void print_fsp_info(void) {

src/drivers/intel/fsp/fsp_util.h

@@ -38,6 +38,7 @@ void chipset_fsp_early_init(FSP_INIT_PARAMS *FspInitParams,
 	FSP_INFO_HEADER *fsp_ptr);
 void ChipsetFspReturnPoint(EFI_STATUS Status, VOID *HobListPtr);
 void * find_saved_temp_mem(void *hob_list_ptr);
+void * find_fsp_reserved_mem(void *hob_list_ptr);
 
 /* functions in hob.c */
 void print_hob_mem_attributes(void *Hobptr);