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);

src/soc/intel/fsp_baytrail/fsp/chipset_fsp_util.h

@@ -32,8 +32,6 @@
 #include <fspvpd.h>
 #include <azalia.h>
 
-#define FSP_RESERVE_MEMORY_SIZE	0x200000
-
 #define FSP_INFO_HEADER_GUID \
   { \
   0x912740BE, 0x2284, 0x4734, {0xB9, 0x71, 0x84, 0xB0, 0x27, 0x35, 0x3F, 0x0C} \

src/soc/intel/fsp_baytrail/memmap.c

@@ -29,18 +29,17 @@ uintptr_t smm_region_start(void)
 	return (iosf_bunit_read(BUNIT_SMRRL) << 20);
 }
 
-/*
- * Calculate the top of usable (low) DRAM.
- * The FSP's reserved memory sits just below the SMM region,
- * allowing calculation of the top of usable memory.
+/** @brief get the top of usable low memory from the FSP's HOB list
+ *
+ * The FSP's reserved memory sits just below the SMM region.  The memory
+ * region below it is usable memory.
  *
  * The entire memory map is shown in northcluster.c
+ *
+ * @return pointer to the first byte of reserved memory
  */
 
 void *cbmem_top(void)
 {
-	uintptr_t tom = smm_region_start();
-	if (!tom)
-		tom = iosf_bunit_read(BUNIT_BMBOUND);
-	return (void *) tom - FSP_RESERVE_MEMORY_SIZE;
+	return find_fsp_reserved_mem(*(void **)CBMEM_FSP_HOB_PTR);
 }

src/soc/intel/fsp_baytrail/northcluster.c

@@ -149,8 +149,7 @@ static void mc_add_dram_resources(device_t dev)
 	uint32_t fsp_mem_base = 0;
 
 	GetHighMemorySize(&highmem_size);
-	GetLowMemorySize(&fsp_mem_base);
-
+	fsp_mem_base=(uint32_t)cbmem_top();
 
 	bmbound = iosf_bunit_read(BUNIT_BMBOUND);
 	bsmmrrl = iosf_bunit_read(BUNIT_SMRRL) << 20;
@@ -162,10 +161,6 @@ static void mc_add_dram_resources(device_t dev)
 
 		printk(BIOS_DEBUG, "FSP memory location: 0x%x\nFSP memory size: %dM\n",
 				fsp_mem_base, (bsmmrrl - fsp_mem_base) >> 20);
-
-		if ((bsmmrrl - fsp_mem_base ) != FSP_RESERVE_MEMORY_SIZE)
-			printk(BIOS_WARNING, "Warning: Fsp memory size does not match "
-					"expected memory size (%x).\n", FSP_RESERVE_MEMORY_SIZE);
 	}
 
 	printk(BIOS_INFO, "Available memory below 4GB: 0x%08x (%dM)\n",