@@ -99,6 +99,30 @@ static int power_init_board(void)
 	return 0;
 }
 
+/* read piggydata via a bootrom callback and place it behind our copy in SDRAM */
+static int imx8m_bootrom_load_image(void)
+{
+	int (*download_image)(u8 *dest, u32 offset, u32 size, u32 xor) = *(void **)0x988;
+	size_t count = __piggydata_end - __piggydata_start;
+	char *p = (char *)MX8M_ATF_BL33_BASE_ADDR + (__piggydata_start - __image_start);
+
+	while (count) {
+		size_t chunksize = min(count, (size_t)1024);
+		int ret;
+
+		ret = download_image(p, 0, chunksize, (uintptr_t)p ^ chunksize);
+		if (ret != 0xf0) {
+			pr_err("Failed to load piggy data (ret = %x)\n", ret);
+			return -EIO;
+		}
+
+		p += chunksize;
+		count -= chunksize;
+	}
+
+	return 0;
+}
+
 extern struct dram_timing_info imx8mp_evk_dram_timing;
 
 static void start_atf(void)

@@ -125,6 +149,9 @@ static void start_atf(void)
 	case BOOTSOURCE_MMC:
 		imx8mp_esdhc_load_image(instance, false);
 		break;
+	case BOOTSOURCE_SERIAL:
+		imx8m_bootrom_load_image();
+		break;
 	default:
 		printf("Unhandled bootsource BOOTSOURCE_%d\n", src);
 		hang();

@@ -495,10 +495,12 @@ static void __imx7_get_boot_source(enum bootsource *src, int *instance,
 	case 5:
 		*src = BOOTSOURCE_NOR;
 		break;
-	case 15:
+	case 14: /* observed on i.MX8MP for USB "serial" booting */
+	case 15: /* observed on i.MX8MM for USB "serial" booting */
 		*src = BOOTSOURCE_SERIAL;
 		break;
 	default:
+		*src = BOOTSOURCE_UNKNOWN;
 		break;
 	}
 }

@@ -9,6 +9,7 @@ extern char _end[];
 extern char __image_start[];
 extern char __image_end[];
 extern char __piggydata_start[];
+extern char __piggydata_end[];
 extern void *_barebox_image_size;
 extern void *_barebox_bare_init_size;
 extern void *_barebox_pbl_size;