plat/st: manage backup partition with FIP

Implement the plat_try_next_boot_source to load
backup partition on specific device.

Change-Id: Ica74596838b339e398c335f9e28ebf60795ab508
Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/tf-a/+/179616


Reviewed-by: CITOOLS <smet-aci-reviews@lists.codex.cro.st.com>
Reviewed-by: Etienne CARRIERE <etienne.carriere@st.com>
Reviewed-by: Yann GAUTIER <yann.gautier@st.com>

plat/st/common/bl2_io_storage.c

@@ -43,6 +43,7 @@ uintptr_t fip_dev_handle;
 uintptr_t storage_dev_handle;
 
 static const io_dev_connector_t *fip_dev_con;
+static uint32_t nand_bkp_offset;
 
 #if STM32MP_SDMMC || STM32MP_EMMC
 static uint32_t block_buffer[MMC_BLOCK_SIZE] __aligned(MMC_BLOCK_SIZE);
@@ -243,6 +244,8 @@ static void boot_fmc2_nand(boot_api_context_t *boot_context)
 	io_result = io_dev_open(nand_dev_con, (uintptr_t)&nand_dev_spec,
 				&storage_dev_handle);
 	assert(io_result == 0);
+
+	nand_bkp_offset = nand_dev_spec.erase_size;
 }
 #endif /* STM32MP_RAW_NAND */
 
@@ -262,6 +265,8 @@ static void boot_spi_nand(boot_api_context_t *boot_context)
 				(uintptr_t)&spi_nand_dev_spec,
 				&storage_dev_handle);
 	assert(io_result == 0);
+
+	nand_bkp_offset = spi_nand_dev_spec.erase_size;
 }
 #endif /* STM32MP_SPI_NAND */
 
@@ -478,3 +483,33 @@ int plat_get_image_source(unsigned int image_id, uintptr_t *dev_handle,
 
 	return rc;
 }
+
+/*
+ * This function shall return 0 if it cannot find an alternate
+ * image to be loaded or it returns 1 otherwise.
+ */
+int plat_try_next_boot_source(unsigned int image_id)
+{
+	static unsigned int backup_id;
+	static unsigned int backup_nb;
+
+	/* No backup available */
+	if (nand_bkp_offset == 0U) {
+		return 0;
+	}
+
+	if (backup_id != image_id) {
+		backup_nb = 0;
+		backup_id = image_id;
+	}
+
+	backup_nb++;
+
+	if (backup_nb >= PLATFORM_MTD_BACKUP_BLOCKS) {
+		return 0;
+	}
+
+	image_block_spec.offset += nand_bkp_offset;
+
+	return 1;
+}