esp32: Improve support for OTA updates.

This commit adds several small items to improve the support for OTA
updates on an esp32:

- a partition table for 4MB flash modules that has two OTA partitions ready
  to go to do updates
- a GENERIC_OTA board that uses that partition table and that enables
  automatic roll-back in the bootloader
- a new esp32.Partition.mark_app_valid_cancel_rollback() class-method to
  signal that the boot is successful and should not be rolled back at the
  next reset
- an automated test for doing an OTA update
- documentation updates

5 files changed, 29 insertions, 0 deletions

diff --git a/ports/esp32/boards/GENERIC_OTA/mpconfigboard.h b/ports/esp32/boards/GENERIC_OTA/mpconfigboard.h
new file mode 100644
index 000000000..ff39c4b2b
--- /dev/null
+++ b/ports/esp32/boards/GENERIC_OTA/mpconfigboard.h
@@ -0,0 +1,2 @@
+#define MICROPY_HW_BOARD_NAME "4MB/OTA module"
+#define MICROPY_HW_MCU_NAME "ESP32"
diff --git a/ports/esp32/boards/GENERIC_OTA/mpconfigboard.mk b/ports/esp32/boards/GENERIC_OTA/mpconfigboard.mk
new file mode 100644
index 000000000..db6492cac
--- /dev/null
+++ b/ports/esp32/boards/GENERIC_OTA/mpconfigboard.mk
@@ -0,0 +1,4 @@
+SDKCONFIG += boards/sdkconfig.base
+SDKCONFIG += boards/GENERIC_OTA/sdkconfig.board
+
+PART_SRC = partitions-ota.csv
diff --git a/ports/esp32/boards/GENERIC_OTA/sdkconfig.board b/ports/esp32/boards/GENERIC_OTA/sdkconfig.board
new file mode 100644
index 000000000..b0ed171d8
--- /dev/null
+++ b/ports/esp32/boards/GENERIC_OTA/sdkconfig.board
@@ -0,0 +1,4 @@
+CONFIG_BOOTLOADER_APP_ROLLBACK_ENABLE=y
+
+# ESP-IDF v3:
+CONFIG_APP_ROLLBACK_ENABLE=y
diff --git a/ports/esp32/esp32_partition.c b/ports/esp32/esp32_partition.c
index cbb62206f..dc2bdd712 100644
--- a/ports/esp32/esp32_partition.c
+++ b/ports/esp32/esp32_partition.c
@@ -209,6 +209,15 @@ STATIC mp_obj_t esp32_partition_get_next_update(mp_obj_t self_in) {
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(esp32_partition_get_next_update_obj, esp32_partition_get_next_update);
 
+STATIC mp_obj_t esp32_partition_mark_app_valid_cancel_rollback(mp_obj_t cls_in) {
+    check_esp_err(esp_ota_mark_app_valid_cancel_rollback());
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(esp32_partition_mark_app_valid_cancel_rollback_fun_obj,
+    esp32_partition_mark_app_valid_cancel_rollback);
+STATIC MP_DEFINE_CONST_CLASSMETHOD_OBJ(esp32_partition_mark_app_valid_cancel_rollback_obj,
+    MP_ROM_PTR(&esp32_partition_mark_app_valid_cancel_rollback_fun_obj));
+
 STATIC const mp_rom_map_elem_t esp32_partition_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_find), MP_ROM_PTR(&esp32_partition_find_obj) },
 
@@ -218,6 +227,7 @@ STATIC const mp_rom_map_elem_t esp32_partition_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_ioctl), MP_ROM_PTR(&esp32_partition_ioctl_obj) },
 
     { MP_ROM_QSTR(MP_QSTR_set_boot), MP_ROM_PTR(&esp32_partition_set_boot_obj) },
+    { MP_ROM_QSTR(MP_QSTR_mark_app_valid_cancel_rollback), MP_ROM_PTR(&esp32_partition_mark_app_valid_cancel_rollback_obj) },
     { MP_ROM_QSTR(MP_QSTR_get_next_update), MP_ROM_PTR(&esp32_partition_get_next_update_obj) },
 
     { MP_ROM_QSTR(MP_QSTR_BOOT), MP_ROM_INT(ESP32_PARTITION_BOOT) },
diff --git a/ports/esp32/partitions-ota.csv b/ports/esp32/partitions-ota.csv
new file mode 100644
index 000000000..007293015
--- /dev/null
+++ b/ports/esp32/partitions-ota.csv
@@ -0,0 +1,9 @@
+# Partition table for MicroPython with OTA support using 4MB flash
+# Name,   Type, SubType, Offset,  Size, Flags
+# Note: if you change the phy_init or app partition offset, make sure to change the offset in Kconfig.projbuild
+nvs,      data, nvs,     0x9000,   0x4000,
+otadata,  data, ota,     0xd000,   0x2000,
+phy_init, data, phy,     0xf000,   0x1000,
+ota_0,    app,  ota_0,   0x10000,  0x180000,
+ota_1,    app,  ota_1,   0x190000, 0x180000,
+vfs,      data, fat,     0x310000, 0x0f0000,