Heaps named by their tags; the STM32F746's DTCM is fast memory too

CMakeLists.txt

@@ -49,6 +49,13 @@ endif()
 
 include(configs/mcu/${TARGET}.cmake)
 
+# The heaps' names - dmheap tags: kinds of memory, separated by commas, that
+# drivers find a heap by (dmheap_get_context_by_name("dma")) and modules ask
+# for (Dmod_MallocTagged("fast", ...)). After the MCU configuration, which
+# says what its memories are.
+set(DMBOOT_DMA_HEAP_TAGS "dma" CACHE STRING "Tags of the DMA heap (linker region dma): dma, and e.g. fast where it is fast internal RAM")
+set(DMBOOT_MAIN_HEAP_TAGS "main" CACHE STRING "Tags of the main heap (linker region ram)")
+
 # Splash logo - after the board configuration, which picks the asset
 set(DMBOOT_SPLASH_LOGO "" CACHE STRING "Splash logo the display driver shows at start: name of an asset in assets/splash/ (e.g. dmodos_logo_128) or a path to a .dmvi file; empty: no logo")
 set(DMBOOT_SPLASH_LOGO_PATH "/eviews/splash_logo.dmvir" CACHE STRING "Path of the splash logo (.dmvir) on the target, passed to the display driver in the SPLASH_LOGO environment variable; empty: not set")
@@ -184,6 +191,8 @@ target_compile_definitions(${MODULE_NAME}.elf
         DMBOOT_SHELL_STRING="${DMBOOT_SHELL}"
         DMBOOT_MAIN_MODULE_ARGS_STRING="${DMBOOT_MAIN_MODULE_ARGS}"
         DMBOOT_SPLASH_LOGO_PATH_STRING="${DMBOOT_SPLASH_LOGO_PATH}"
+        DMBOOT_DMA_HEAP_TAGS_STRING="${DMBOOT_DMA_HEAP_TAGS}"
+        DMBOOT_MAIN_HEAP_TAGS_STRING="${DMBOOT_MAIN_HEAP_TAGS}"
 )
 
 target_link_options(${MODULE_NAME}.elf

README.md

@@ -279,6 +279,17 @@ dmlcdtft), the `dma` heap is the DTCM, which is never cached, and the module
 loader calls `Dmod_SyncCode()` once a module is in place, so its code
 reaches the instruction fetch.
 
+### Heaps and their tags
+
+A heap's name is the list of its tags - kinds of memory (dmheap): drivers find
+the DMA heap by a tag (`dmheap_get_context_by_name("dma")`), modules ask for
+memory of a kind with `Dmod_MallocTagged("fast", ...)` and get the default
+memory when there is none. `DMBOOT_DMA_HEAP_TAGS` and `DMBOOT_MAIN_HEAP_TAGS`
+name the heaps (`dma`, `main` by default); an MCU's configuration says what its
+memories are - the STM32F746's DMA heap is the DTCM, `dma,fast,dtcm`: the
+fastest RAM there is, given to what is worked on all the time (dmmp3's decoder
+state: 70 % of the CPU in the SDRAM, 15 % there).
+
 ### `monitor-gdb`
 Monitor logs from the firmware in real-time via GDB server. This target:
 - Automatically builds the `dmlog_monitor` tool for the host architecture

configs/board/stm32f746g-disco/flash.dmd

@@ -118,3 +118,9 @@ dmview@>=0.10 rules=dmview.rules
 # files of the card's music/ directory through dmaudio.
 #
 carhmi service=carhmi.ini
+#
+# The decoders of the album covers carhmi makes of the MP3 files' pictures:
+# dmimg finds them by name, so they are not in carhmi's dependencies.
+#
+dmimg_jpeg
+dmimg_png

configs/mcu/STM32F746ZG.cmake

@@ -27,6 +27,15 @@ set(OPENOCD_TARGET "target/stm32f7x.cfg" CACHE STRING "OpenOCD target configurat
 # Name of the target cpu (if empty, the target is generic)
 set(DMOD_CPU_NAME   ${DMBOOT_MCU_NAME} CACHE STRING "Name of the target cpu, if empty, the target is generic")
 
+# ======================================================================
+#               Heaps
+# ======================================================================
+# The DMA heap is the DTCM: reached by DMA through the core's AHBS port, never
+# in the data cache - and the fastest RAM there is (no wait states, beside the
+# cache): also what modules get when they ask for "fast" memory (e.g. dmmp3's
+# decoder state - 70 % of the CPU in the SDRAM, 15 % here)
+set(DMBOOT_DMA_HEAP_TAGS "dma,fast,dtcm" CACHE STRING "Tags of the DMA heap (linker region dma)")
+
 # ======================================================================
 #               Renode Configuration
 # ======================================================================

configs/mcu/STM32F746xG.cmake

@@ -28,6 +28,15 @@ set(OPENOCD_TARGET "target/stm32f7x.cfg" CACHE STRING "OpenOCD target configurat
 set(DMOD_CPU_NAME   ${DMBOOT_MCU_NAME} CACHE STRING "Name of the target cpu, if empty, the target is generic")
 set(DMBOOT_IRQ_COUNT 98 CACHE STRING "Number of external IRQ lines for this MCU")
 
+# ======================================================================
+#               Heaps
+# ======================================================================
+# The DMA heap is the DTCM: reached by DMA through the core's AHBS port, never
+# in the data cache - and the fastest RAM there is (no wait states, beside the
+# cache): also what modules get when they ask for "fast" memory (e.g. dmmp3's
+# decoder state - 70 % of the CPU in the SDRAM, 15 % here)
+set(DMBOOT_DMA_HEAP_TAGS "dma,fast,dtcm" CACHE STRING "Tags of the DMA heap (linker region dma)")
+
 # ======================================================================
 #               Renode Configuration
 # ======================================================================

src/main.c

@@ -595,10 +595,10 @@ int main(int argc, char** argv)
     dmlog_set_as_default(ctx);
 
     // Initialize the DMA-capable heap (named "dma"), if the target defines one
-    init_heap(&__dma_start__, &__dma_end__, "dma", false);
+    init_heap(&__dma_start__, &__dma_end__, DMBOOT_DMA_HEAP_TAGS_STRING, false);
 
     // Initialize the main heap; a failure here is unrecoverable
-    init_heap(&__heap_start__, &__heap_end__, "main", true);
+    init_heap(&__heap_start__, &__heap_end__, DMBOOT_MAIN_HEAP_TAGS_STRING, true);
 
     dmenv_ctx_t dmenv_ctx = dmenv_create(NULL);
     if(dmenv_ctx == NULL)