esp32: Allow fixed static RAM size and DRAM heap size

Merges https://github.com/espressif/esp-idf/pull/3222

components/bootloader/subproject/main/esp32.bootloader.ld

@@ -149,7 +149,6 @@ SECTIONS
     *(.gnu.linkonce.lit4.*)
     _lit4_end = ABSOLUTE(.);
     . = ALIGN(4);
-    _heap_start = ABSOLUTE(.);
   } >dram_seg
 
   .iram.text :

components/esp32/Kconfig

@@ -719,6 +719,27 @@ menu "ESP32-specific"
             This option depends on the CONFIG_FREERTOS_UNICORE option because RTC fast memory
             can be accessed only by PRO_CPU core.
 
+    config ESP32_USE_FIXED_STATIC_RAM_SIZE
+        bool "Use fixed static RAM size"
+        default n
+        help
+            If this option is disabled, the DRAM part of the heap starts right after the .bss section,
+            within the dram0_0 region. As a result, adding or removing some static variables
+            will change the available heap size.
+
+            If this option is enabled, the DRAM part of the heap starts right after the dram0_0 region,
+            where its length is set with ESP32_FIXED_STATIC_RAM_SIZE
+
+    config ESP32_FIXED_STATIC_RAM_SIZE
+        hex "Fixed Static RAM size"
+        default 0x1E000
+        range 0 0x2c200
+        depends on ESP32_USE_FIXED_STATIC_RAM_SIZE
+        help
+            RAM size dedicated for static variables (.data & .bss sections).
+            Please note that the actual length will be reduced by BT_RESERVE_DRAM if Bluetooth
+            controller is enabled.
+
 endmenu  # ESP32-Specific
 
 menu "Power Management"

components/esp32/ld/esp32.ld

@@ -21,6 +21,17 @@
 #define CONFIG_BT_RESERVE_DRAM 0
 #endif
 
+#if defined(CONFIG_ESP32_USE_FIXED_STATIC_RAM_SIZE)
+
+ASSERT((CONFIG_ESP32_FIXED_STATIC_RAM_SIZE <= 0x2c200),
+          "Fixed static ram data does not fit.")
+
+#define DRAM0_0_SEG_LEN CONFIG_ESP32_FIXED_STATIC_RAM_SIZE
+
+#else
+#define DRAM0_0_SEG_LEN 0x2c200
+#endif
+
 MEMORY
 {
   /* All these values assume the flash cache is on, and have the blocks this uses subtracted from the length
@@ -51,7 +62,7 @@ MEMORY
      additional static memory temporarily cannot be used.
   */
   dram0_0_seg (RW) :                 org = 0x3FFB0000 + CONFIG_BT_RESERVE_DRAM,
-                                     len = 0x2c200 - CONFIG_BT_RESERVE_DRAM
+                                     len = DRAM0_0_SEG_LEN - CONFIG_BT_RESERVE_DRAM
 
   /* Flash mapped constant data */
   drom0_0_seg (R) :                  org = 0x3F400018, len = 0x400000-0x18
@@ -61,7 +72,7 @@ MEMORY
   /* RTC fast memory (executable). Persists over deep sleep.
    */
   rtc_iram_seg(RWX) :                org = 0x400C0000, len = 0x2000
-  
+
   /* RTC fast memory (same block as above), viewed from data bus */
   rtc_data_seg(RW) :                 org = 0x3ff80000, len = 0x2000
 
@@ -77,14 +88,21 @@ MEMORY
                                      len = 0x400000
 }
 
+#if defined(CONFIG_ESP32_USE_FIXED_STATIC_RAM_SIZE)
+/* static data ends at defined address */
+_static_data_end = 0x3FFB0000 + DRAM0_0_SEG_LEN;
+#else
+_static_data_end = _bss_end;
+#endif
+
 /* Heap ends at top of dram0_0_seg */
 _heap_end = 0x40000000 - CONFIG_ESP32_TRACEMEM_RESERVE_DRAM;
 
 _data_seg_org = ORIGIN(rtc_data_seg);
 
-/* The lines below define location alias for .rtc.data section based on Kconfig option. 
-   When the option is not defined then use slow memory segment 
-   else the data will be placed in fast memory segment */ 
+/* The lines below define location alias for .rtc.data section based on Kconfig option.
+   When the option is not defined then use slow memory segment
+   else the data will be placed in fast memory segment */
 #ifndef CONFIG_ESP32_RTCDATA_IN_FAST_MEM
 REGION_ALIAS("rtc_data_location", rtc_slow_seg );
 #else

components/esp32/ld/esp32.project.ld.in

@@ -239,8 +239,6 @@ SECTIONS
 
     . = ALIGN (8);
     _bss_end = ABSOLUTE(.);
-    /* The heap starts right after end of this section */
-    _heap_start = ABSOLUTE(.);
   } > dram0_0_seg
 
   ASSERT(((_bss_end - ORIGIN(dram0_0_seg)) <= LENGTH(dram0_0_seg)),

components/soc/src/memory_layout_utils.c

@@ -29,7 +29,7 @@ extern soc_reserved_region_t soc_reserved_memory_region_end;
 These variables have the start and end of the data and static IRAM
 area used by the program. Defined in the linker script.
 */
-extern int _data_start, _bss_end, _iram_start, _iram_end;
+extern int _data_start, _static_data_end, _iram_start, _iram_end;
 
 /* static DRAM & IRAM chunks */
 static const size_t EXTRA_RESERVED_REGIONS = 2;
@@ -68,7 +68,7 @@ static void s_prepare_reserved_regions(soc_reserved_region_t *reserved, size_t c
 
     /* Add the EXTRA_RESERVED_REGIONS at the beginning */
     reserved[0].start = (intptr_t)&_data_start; /* DRAM used by data+bss */
-    reserved[0].end = (intptr_t)&_bss_end;
+    reserved[0].end = (intptr_t)&_static_data_end;
     reserved[1].start = (intptr_t)&_iram_start; /* IRAM used by code */
     reserved[1].end = (intptr_t)&_iram_end;
 

tools/ldgen/samples/template.ld

@@ -134,7 +134,6 @@ SECTIONS
 
     . = ALIGN (8);
     _bss_end = ABSOLUTE(.);
-    _heap_start = ABSOLUTE(.);
   } >dram0_0_seg
 
   .flash.rodata :