Spiram: Add option to reserve MMU banks; add himem API to make use of those banks

components/esp32/Kconfig

@@ -67,15 +67,24 @@ endchoice
 
 choice SPIRAM_TYPE
     prompt "Type of SPI RAM chip in use"
-    default SPIRAM_TYPE_ESPPSRAM32
+    default SPIRAM_TYPE_AUTO
+
+config SPIRAM_TYPE_AUTO
+    bool "Auto-detect"
 
 config SPIRAM_TYPE_ESPPSRAM32
     bool "ESP-PSRAM32 or IS25WP032"
+
+config SPIRAM_TYPE_ESPPSRAM64
+    bool "ESP-PSRAM64 or LY68L6400"
+
 endchoice
 
 config SPIRAM_SIZE
     int
+    default -1 if SPIRAM_TYPE_AUTO
     default 4194304 if SPIRAM_TYPE_ESPPSRAM32
+    default 8388608 if SPIRAM_TYPE_ESPPSRAM64
     default 0
 
 choice SPIRAM_SPEED
@@ -120,6 +129,29 @@ config SPIRAM_CACHE_WORKAROUND
         This will also not use any bits of newlib that are located in ROM, opting for a version that is compiled
         with the workaround and located in flash instead.
 
+config SPIRAM_BANKSWITCH_ENABLE
+    bool "Enable bank switching for >4MiB external RAM"
+    default y
+    depends on SPIRAM_USE_MEMMAP || SPIRAM_USE_CAPS_ALLOC || SPIRAM_USE_MALLOC
+    help
+        The ESP32 only supports 4MiB of external RAM in its address space. The hardware does support larger
+        memories, but these have to be bank-switched in and out of this address space. Enabling this allows you
+        to reserve some MMU pages for this, which allows the use of the esp_himem api to manage these banks.
+
+#Note that this is limited to 62 banks, as esp_spiram_writeback_cache needs some kind of mapping of some banks
+#below that mark to work. We cannot at this moment guarantee this to exist when himem is enabled.
+config SPIRAM_BANKSWITCH_RESERVE
+    int "Amount of 32K pages to reserve for bank switching"
+    depends on SPIRAM_BANKSWITCH_ENABLE
+    default 8
+    range 1 62
+    help
+        Select the amount of banks reserved for bank switching. Note that the amount of RAM allocatable with 
+        malloc/esp_heap_alloc_caps will decrease by 32K for each page reserved here.
+        
+        Note that this reservation is only actually done if your program actually uses the himem API. Without
+        any himem calls, the reservation is not done and the original amount of memory will be available
+        to malloc/esp_heap_alloc_caps.
 
 config SPIRAM_MALLOC_ALWAYSINTERNAL
     int "Maximum malloc() size, in bytes, to always put in internal memory"