system: add kconfig option for using parts of SRAM1 for IRAM

Using parts of SRAM1 for IRAM allows apps with more statically allocated IRAM

Closes https://github.com/espressif/esp-idf/issues/9824

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

@@ -25,7 +25,7 @@ MEMORY
   */
   iram_seg (RWX) :                  org = 0x40080400, len = 0xfc00
   /* 64k at the end of DRAM, after ROM bootloader stack */
-  dram_seg (RW) :                  	org = 0x3FFF0000, len = 0x10000
+  dram_seg (RW) :                  	org = 0x3FFF0000, len = 0x6000
 }
 
 /*  Default entry point:  */

components/esp_system/ld/esp32/memory.ld.in

@@ -48,6 +48,13 @@ ASSERT((CONFIG_ESP32_FIXED_STATIC_RAM_SIZE <= 0x2c200),
 #define DRAM0_0_SEG_LEN 0x2c200
 #endif
 
+#if CONFIG_ESP_SYSTEM_ESP32_SRAM1_REGION_AS_IRAM
+#define SRAM1_IRAM_LEN 0xA000
+#else
+#define SRAM1_IRAM_LEN 0x0
+#endif
+
+
 MEMORY
 {
   /* All these values assume the flash cache is on, and have the blocks this uses subtracted from the length
@@ -55,7 +62,7 @@ MEMORY
   are connected to the data port of the CPU and eg allow bytewise access. */
 
   /* IRAM for PRO cpu. Not sure if happy with this, this is MMU area... */
-  iram0_0_seg (RX) :                 org = 0x40080000, len = 0x20000
+  iram0_0_seg (RX) :                 org = 0x40080000, len = 0x20000 + SRAM1_IRAM_LEN
 
 #ifdef CONFIG_APP_BUILD_USE_FLASH_SECTIONS
   /* Even though the segment name is iram, it is actually mapped to flash
@@ -121,8 +128,14 @@ _heap_start = 0x3FFB0000 + DRAM0_0_SEG_LEN;
 _heap_start = _heap_low_start;
 #endif
 
-/* Heap ends at top of dram0_0_seg */
+_sram1_iram_start = 0x400A0000;
+_sram1_iram_len = ( _iram_end > _sram1_iram_start) ? (_iram_end - _sram1_iram_start) : 0;
+_heap_end = ALIGN(0x40000000 - _sram1_iram_len - 3, 4);
+
+#if CONFIG_ESP32_TRACEMEM_RESERVE_DRAM != 0
 _heap_end = 0x40000000 - CONFIG_ESP32_TRACEMEM_RESERVE_DRAM;
+#endif
+
 
 _data_seg_org = ORIGIN(rtc_data_seg);
 

components/esp_system/port/soc/esp32/Kconfig.memory

@@ -41,4 +41,19 @@ menu "Memory"
             This is possible due to handling of exceptions `LoadStoreError (3)` and `LoadStoreAlignmentError (9)`
             Each unaligned read/write access will incur a penalty of maximum of 167 CPU cycles.
 
+    menu "Non-backward compatible options"
+
+        config ESP_SYSTEM_ESP32_SRAM1_REGION_AS_IRAM
+            bool "Reserve parts of SRAM1 for app IRAM (WARNING, read help before enabling)"
+            depends on !ESP32_TRAX
+            help
+                Reserve parts of SRAM1 for app IRAM which was previously reserved for bootloader DRAM.
+                If booting an app on an older bootloader from before this option was introduced, the app may fail
+                to boot due to overlapping memory areas. If this is the case please test carefully before pushing out
+                any OTA updates.
+
+                The bootloader DRAM memory should be sufficient for any non-modified IDF bootloader.
+
+    endmenu
+
 endmenu # Memory

components/heap/port/esp32/memory_layout.c

@@ -172,7 +172,7 @@ SOC_RESERVE_MEMORY_REGION(0x3fffc000, 0x40000000, trace_mem); //Reserve trace me
 SOC_RESERVE_MEMORY_REGION(SOC_EXTRAM_DATA_LOW, SOC_EXTRAM_DATA_HIGH, spi_ram);
 #endif
 
-extern int _data_start, _heap_start, _iram_start, _iram_end, _rtc_force_fast_end, _rtc_noinit_end;
+extern int _data_start, _heap_start, _heap_end, _iram_start, _iram_end, _rtc_force_fast_end, _rtc_noinit_end;
 // Static data region. DRAM used by data+bss and possibly rodata
 SOC_RESERVE_MEMORY_REGION((intptr_t)&_data_start, (intptr_t)&_heap_start, dram_data);
 
@@ -180,6 +180,11 @@ SOC_RESERVE_MEMORY_REGION((intptr_t)&_data_start, (intptr_t)&_heap_start, dram_d
 // ESP32 has an IRAM-only region 0x4008_0000 - 0x4009_FFFF, reserve the used part
 SOC_RESERVE_MEMORY_REGION((intptr_t)&_iram_start, (intptr_t)&_iram_end, iram_code);
 
+// If IRAM spans into SRAM1 due to CONFIG_ESP_SYSTEM_ESP32_SRAM1_REGION_AS_IRAM, reserve the corresponding part of DRAM
+#ifdef CONFIG_ESP_SYSTEM_ESP32_SRAM1_REGION_AS_IRAM
+SOC_RESERVE_MEMORY_REGION((intptr_t) &_heap_end, 0x40000000, sram1_iram);
+#endif
+
 // RTC Fast RAM region
 #ifdef CONFIG_ESP_SYSTEM_ALLOW_RTC_FAST_MEM_AS_HEAP
 #ifdef CONFIG_ESP32_RTCDATA_IN_FAST_MEM

components/soc/esp32/include/soc/soc.h

@@ -182,7 +182,7 @@
 #define SOC_CACHE_APP_LOW       0x40078000
 #define SOC_CACHE_APP_HIGH      0x40080000
 #define SOC_IRAM_LOW            0x40080000
-#define SOC_IRAM_HIGH           0x400A0000
+#define SOC_IRAM_HIGH           0x400AA000
 #define SOC_RTC_IRAM_LOW        0x400C0000
 #define SOC_RTC_IRAM_HIGH       0x400C2000
 #define SOC_RTC_DRAM_LOW        0x3FF80000

docs/en/api-guides/performance/ram-usage.rst

@@ -142,6 +142,29 @@ The following options will reduce IRAM usage of some ESP-IDF features:
     - Setting :ref:`CONFIG_HAL_DEFAULT_ASSERTION_LEVEL` to disable assertion for HAL component will save some IRAM especially for HAL code who calls `HAL_ASSERT` a lot and resides in IRAM.
     - Refer to sdkconfig menu ``Auto-detect flash chips`` and you can disable flash drivers which you don't need to save some IRAM.
 
+.. only:: esp32
+
+   Using SRAM1 for IRAM
+   ^^^^^^^^^^^^^^^^^^^^
+
+   The SRAM1 memory area is normally used for DRAM, but it is possible to use parts of it for IRAM with :ref:`CONFIG_ESP_SYSTEM_ESP32_SRAM1_REGION_AS_IRAM`. This memory would previously be reserved for DRAM data usage (e.g. bss) by the software bootloader and later added to the heap. After this option was introduced, the bootloader DRAM size was reduced to a value closer to what it normally actually needs.
+
+   When compiling with this config option, the linker will make sure that both the app's IRAM section and the bootloader's DRAM section is sufficiently large, and not overlapping. If the software bootloader was compiled before this option existed, then it is guaranteed that these two sections will not overlap. This would typically happen if you are doing an OTA update, where only the app would be updated.
+
+   If the IRAM section were to overlap the bootloader's DRAM section then this would be detected during the bootup process and result in a failed boot:
+
+   .. code-block:: text
+
+      E (204) esp_image: _dram_start = 0x3fff0000, _dram_end = 0x3fff1be0
+      E (208) esp_image: Segment 4 0x3fff14e0-0x3ffffffc invalid: overlaps bootloader data
+
+   .. warning::
+
+      Apps compiled with :ref:`CONFIG_ESP_SYSTEM_ESP32_SRAM1_REGION_AS_IRAM`, may fail to boot if used together with a software bootloader compiled without the config option.
+
+   Currently the software bootloader compiled with security features enabled uses less than 16KB of DRAM, which means that even when allocating the entirety of this IRAM (40KB), there should still be some spare room. However, as this is not guaranteed, we recommended thoroughly testing before pushing an app update with this option enabled.
+
+   Any memory which ends up not being used for static IRAM will be added to the heap.
 
 .. only:: esp32c3
 

tools/ci/build_template_app.sh

@@ -23,6 +23,8 @@ gen_configs() {
     # CONFIG_COMPILER_OPTIMIZATION_PERF with flag -O2
     echo "CONFIG_COMPILER_OPTIMIZATION_PERF=y" > esp-idf-template/sdkconfig.ci.O2
     echo "CONFIG_BOOTLOADER_COMPILER_OPTIMIZATION_PERF=y" >> esp-idf-template/sdkconfig.ci.O2
+    # -O2 makes the bootloader too large to fit in the default space, otherwise(!)
+    echo "CONFIG_PARTITION_TABLE_OFFSET=0x10000" >> esp-idf-template/sdkconfig.ci.O2
 
     # This part will be built in earlier stage (pre_build job) with only cmake. Built with make in later stage
     # CONFIG_COMPILER_OPTIMIZATION_DEFAULT with flag -Og

tools/test_apps/system/startup/sdkconfig.ci.sram1_iram

@@ -0,0 +1,3 @@
+# Only ESP32 has this option
+CONFIG_IDF_TARGET="esp32"
+CONFIG_ESP_SYSTEM_ESP32_SRAM1_REGION_AS_IRAM=y