app: Fix full modem update completion flow

Move full modem FOTA setup into a shared helper used by both start and
finish paths. Reconfigure full modem update storage and load firmware
using the resolved flash device and offset in the completion path.

Also set pm-ext-flash in board overlay for external partition support.

Signed-off-by: Syver Haraldsen <syver.haraldsen@nordicsemi.no>
(cherry picked from commit 448cf99)

Author: SyverHaraldsen

app/boards/nrf9151dk_nrf9151_ns.overlay

@@ -7,6 +7,7 @@
 / {
 	chosen {
 		ncs,sm-uart = &dtr_uart0;
+		nordic,pm-ext-flash = &gd25wb256;
 	};
 };
 

app/src/sm_at_fota.c

@@ -64,12 +64,53 @@ static char hostname[URI_HOST_MAX];
 static uint8_t fmfu_buf[FMFU_BUF_SIZE];
 
 /* External flash device for full modem firmware storage */
+#if !defined(CONFIG_DFU_TARGET_FULL_MODEM_USE_EXT_PARTITION)
 #define FLASH_NODE DT_COMPAT_GET_ANY_STATUS_OKAY(jedec_spi_nor)
 static const struct device *flash_dev = DEVICE_DT_GET(FLASH_NODE);
+#endif
 
 /* dfu_target specific configurations */
 static struct dfu_target_fmfu_fdev fdev;
 static struct dfu_target_full_modem_params full_modem_fota_params;
+
+/* Setup full modem FOTA configuration */
+static int setup_full_modem_fota_config(void)
+{
+	int err;
+
+	full_modem_fota_params.buf = fmfu_buf;
+	full_modem_fota_params.len = sizeof(fmfu_buf);
+	full_modem_fota_params.dev = &fdev;
+
+#if defined(CONFIG_DFU_TARGET_FULL_MODEM_USE_EXT_PARTITION)
+	fdev.dev = NULL;
+	fdev.offset = 0;
+	fdev.size = 0;
+#else
+	fdev.dev = flash_dev;
+	fdev.offset = 0;
+	fdev.size = DT_PROP(FLASH_NODE, size) / 8;
+
+	if (!device_is_ready(flash_dev)) {
+		LOG_ERR("Flash device %s not ready", flash_dev->name);
+		return -ENXIO;
+	}
+#endif
+
+	err = dfu_target_full_modem_cfg(&full_modem_fota_params);
+	if (err != 0 && err != -EALREADY) {
+		LOG_ERR("dfu_target_full_modem_cfg failed: %d", err);
+		return err;
+	}
+
+	err = dfu_target_full_modem_fdev_get(&fdev);
+	if (err != 0) {
+		LOG_ERR("dfu_target_full_modem_fdev_get failed: %d", err);
+		return err;
+	}
+
+	return 0;
+}
 #endif
 
 static int do_fota_mfw_read(void)
@@ -334,24 +375,11 @@ static int handle_at_fota(enum at_parser_cmd_type cmd_type, struct at_parser *pa
 				type = DFU_TARGET_IMAGE_TYPE_MCUBOOT;
 			}
 #if defined(CONFIG_SM_FULL_FOTA)
-			else if (op == SM_FOTA_START_FULL_FOTA)  {
-				fdev.dev = flash_dev;
-				fdev.size = DT_PROP(FLASH_NODE, size) / 8;
-				full_modem_fota_params.buf = fmfu_buf;
-				full_modem_fota_params.len = sizeof(fmfu_buf);
-				full_modem_fota_params.dev = &fdev;
-
-				if (!device_is_ready(flash_dev)) {
-					LOG_ERR("Flash device %s not ready", flash_dev->name);
-					return -ENXIO;
-				}
-
-				err = dfu_target_full_modem_cfg(&full_modem_fota_params);
-				if (err != 0 && err != -EALREADY) {
-					LOG_ERR("dfu_target_full_modem_cfg failed: %d", err);
+			else if (op == SM_FOTA_START_FULL_FOTA) {
+				err = setup_full_modem_fota_config();
+				if (err != 0) {
 					return err;
 				}
-
 				type = DFU_TARGET_IMAGE_TYPE_FULL_MODEM;
 			}
 #endif
@@ -516,8 +544,13 @@ void sm_finish_modem_full_fota(void)
 		handle_full_fota_activation_fail(err);
 	}
 
-	/* Loading data from external flash to modem's flash. */
-	err = fmfu_fdev_load(fmfu_buf, sizeof(fmfu_buf), flash_dev, 0);
+	/* Re-establish dfu_target configuration after reboot */
+	err = setup_full_modem_fota_config();
+	if (err != 0) {
+		handle_full_fota_activation_fail(err);
+	}
+
+	err = fmfu_fdev_load(fmfu_buf, sizeof(fmfu_buf), fdev.dev, fdev.offset);
 	if (err != 0) {
 		LOG_ERR("fmfu_fdev_load failed: %d", err);
 		handle_full_fota_activation_fail(err);
@@ -529,16 +562,9 @@ void sm_finish_modem_full_fota(void)
 		handle_full_fota_activation_fail(err);
 	}
 
-	/* Reset dfu_target to a pristine state, otherwise it has been observed to
-	 * fail when attempting a second full MFW update without application reset.
-	 */
-	err = fota_download_util_image_reset(DFU_TARGET_IMAGE_TYPE_FULL_MODEM);
-	if (err) {
-		LOG_ERR("fota_download_util_image_reset() failed: %d\n", err);
-	}
-
 	sm_fota_status = FOTA_STATUS_OK;
 	sm_fota_info = 0;
+
 	LOG_INF("Full modem firmware update complete.");
 }