esp32/boards/ESP32_GENERIC_S3: Add 4MiB partitioning board variant.

Added a 4MiB flash partitioning variant for ESP32S3: adds support for 4MiB
discrete flash boards or ESP32-S3FH4R2 with embedded 4MiB flash based ones.

Tested on the waveshare ESP32-S3 Mini w/ESP32-S3FH4R2.

Signed-off-by: Stanislav Ponomarev <me@stasponomarev.com>

ports/esp32/boards/ESP32_GENERIC_S3/board.json

@@ -18,6 +18,7 @@
     "url": "https://www.espressif.com/en/products/modules",
     "vendor": "Espressif",
     "variants": {
-        "SPIRAM_OCT": "Support for Octal-SPIRAM"
+        "SPIRAM_OCT": "Support for Octal-SPIRAM",
+        "FLASH_4M": "4MiB flash"
     }
 }

ports/esp32/boards/ESP32_GENERIC_S3/board.md

@@ -1,7 +1,9 @@
 The following files are firmware that should work on most ESP32-S3-based
-boards with 8MiB of flash, including WROOM and MINI modules.
+boards with 4/8MiB of flash, including WROOM and MINI modules.
 
 This firmware supports configurations with and without SPIRAM (also known as
 PSRAM) and will auto-detect a connected SPIRAM chip at startup and allocate
 the MicroPython heap accordingly. However if your board has Octal SPIRAM, then
 use the "spiram-oct" variant.
+
+If your board has 4MiB flash (including ESP32-S3FH4R2 based ones with embedded flash), then use the "flash-4m" build.

ports/esp32/boards/ESP32_GENERIC_S3/mpconfigboard.cmake

@@ -20,3 +20,10 @@ if(MICROPY_BOARD_VARIANT STREQUAL "SPIRAM_OCT")
         MICROPY_HW_BOARD_NAME="Generic ESP32S3 module with Octal-SPIRAM"
     )
 endif()
+
+if(MICROPY_BOARD_VARIANT STREQUAL "FLASH_4M")
+    set(SDKCONFIG_DEFAULTS
+        ${SDKCONFIG_DEFAULTS}
+        boards/ESP32_GENERIC_S3/sdkconfig.flash_4m
+    )
+endif()

ports/esp32/boards/ESP32_GENERIC_S3/sdkconfig.flash_4m

@@ -0,0 +1,4 @@
+CONFIG_ESPTOOLPY_FLASHSIZE_4MB=y
+CONFIG_ESPTOOLPY_FLASHSIZE_8MB=
+
+CONFIG_PARTITION_TABLE_CUSTOM_FILENAME="partitions-4MiB.csv"