feat(arm): add IO policy to use backup gpt header

Add a IO block spec to use GPT backup header if primary fails.
Currently we use only the primary gpt header which is in the second
block(LBA-1) after the MBR block(LBA-0) so we restrict IO access to
primary gpt header and its entries.

But we plan to use backup GPT which is the last block of the
partition (LBA-n) in case our primary GPT header fails verification
or is corrupted.

Offset and length of the block spec will be updated runtime from
partition driver after parsing MBR data.

Change-Id: Id1d49841d6f4cbcc3248af19faf2fbd8e24a8ba1
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>

plat/arm/common/fconf/arm_fconf_io.c

@@ -50,6 +50,18 @@ static const io_block_spec_t gpt_spec = {
 	.length         = PLAT_PARTITION_BLOCK_SIZE *
 			  (PLAT_PARTITION_MAX_ENTRIES / 4 + 2),
 };
+
+/*
+ * length will be assigned at runtime based on MBR header data.
+ * Backup GPT Header is present in Last LBA-1 and its entries
+ * are last 32 blocks starts at LBA-33, On runtime update these
+ * before device usage. Update offset to beginning LBA-33 and
+ * length to LBA-33.
+ */
+static io_block_spec_t bkup_gpt_spec = {
+	.offset         = PLAT_ARM_FLASH_IMAGE_BASE,
+	.length         = 0,
+};
 #endif /* ARM_GPT_SUPPORT */
 
 const io_uuid_spec_t arm_uuid_spec[MAX_NUMBER_IDS] = {
@@ -107,6 +119,11 @@ struct plat_io_policy policies[MAX_NUMBER_IDS] = {
 		(uintptr_t)&gpt_spec,
 		open_memmap
 	},
+	[BKUP_GPT_IMAGE_ID] = {
+		&memmap_dev_handle,
+		(uintptr_t)&bkup_gpt_spec,
+		open_memmap
+	},
 #endif /* ARM_GPT_SUPPORT */
 #if PSA_FWU_SUPPORT
 	[FWU_METADATA_IMAGE_ID] = {