esp32: Use SPIRAM in mem-map mode so all of it can be used for uPy heap.

Also enable CONFIG_SPIRAM_IGNORE_NOTFOUND to allow boards with faulty or
missing SPIRAM to still boot.

ports/esp32/boards/sdkconfig.spiram

@@ -13,6 +13,8 @@ CONFIG_LOG_BOOTLOADER_LEVEL_WARN=y
 # ESP32-specific
 CONFIG_ESP32_DEFAULT_CPU_FREQ_240=y
 CONFIG_SPIRAM_SUPPORT=y
+CONFIG_SPIRAM_IGNORE_NOTFOUND=y
+CONFIG_SPIRAM_USE_MEMMAP=y
 CONFIG_TASK_WDT_CHECK_IDLE_TASK_CPU0=n
 CONFIG_ESP32_XTAL_FREQ_AUTO=y
 

ports/esp32/main.c

@@ -37,6 +37,7 @@
 #include "esp_task.h"
 #include "soc/cpu.h"
 #include "esp_log.h"
+#include "esp_spiram.h"
 
 #include "py/stackctrl.h"
 #include "py/nlr.h"
@@ -69,9 +70,29 @@ void mp_task(void *pvParameter) {
     #endif
     uart_init();
 
+    #if CONFIG_SPIRAM_SUPPORT
+    // Try to use the entire external SPIRAM directly for the heap
+    size_t mp_task_heap_size;
+    void *mp_task_heap = (void*)0x3f800000;
+    switch (esp_spiram_get_chip_size()) {
+        case ESP_SPIRAM_SIZE_16MBITS:
+            mp_task_heap_size = 2 * 1024 * 1024;
+            break;
+        case ESP_SPIRAM_SIZE_32MBITS:
+        case ESP_SPIRAM_SIZE_64MBITS:
+            mp_task_heap_size = 4 * 1024 * 1024;
+            break;
+        default:
+            // No SPIRAM, fallback to normal allocation
+            mp_task_heap_size = heap_caps_get_largest_free_block(MALLOC_CAP_8BIT);
+            mp_task_heap = malloc(mp_task_heap_size);
+            break;
+    }
+    #else
     // Allocate the uPy heap using malloc and get the largest available region
     size_t mp_task_heap_size = heap_caps_get_largest_free_block(MALLOC_CAP_8BIT);
     void *mp_task_heap = malloc(mp_task_heap_size);
+    #endif
 
 soft_reset:
     // initialise the stack pointer for the main thread