HAL_ChibiOS: added a DMA reserve heap

this ensures we keep some DMA-capable memory aside for when it is
needed

libraries/AP_HAL_ChibiOS/hwdef/common/board.c

@@ -17,6 +17,7 @@
 
 #include "hal.h"
 #include "usbcfg.h"
+#include "stm32_util.h"
 
 #if HAL_USE_PAL || defined(__DOXYGEN__)
 /**
@@ -64,6 +65,9 @@ void __early_init(void) {
 void __late_init(void) {
   halInit();
   chSysInit();
+#if CH_CFG_USE_HEAP == TRUE
+  malloc_init();
+#endif
 #ifdef HAL_USB_PRODUCT_ID
   setup_usb_strings();
 #endif

libraries/AP_HAL_ChibiOS/hwdef/common/malloc.c

@@ -41,22 +41,49 @@
 
 #if defined(CCM_RAM_SIZE_KB)
 static memory_heap_t ccm_heap;
-static bool ccm_heap_initialised = false;
 #endif
 
 #if defined(DTCM_RAM_SIZE_KB)
 static memory_heap_t dtcm_heap;
-static bool dtcm_heap_initialised = false;
 #endif
 
+// size of memory reserved for dma-capable alloc
+#ifndef DMA_RESERVE_SIZE
+#define DMA_RESERVE_SIZE 4096
+#endif
+
+static memory_heap_t dma_reserve_heap;
+
+static void *malloc_dtcm(size_t size);
+
+/*
+  initialise memory handling
+ */
+void malloc_init(void)
+{
+#if defined(CCM_RAM_SIZE_KB)
+    chHeapObjectInit(&ccm_heap, (void *)CCM_BASE_ADDRESS, CCM_RAM_SIZE_KB*1024);
+#endif
+
+#if defined(DTCM_RAM_SIZE_KB)
+    chHeapObjectInit(&dtcm_heap, (void *)DTCM_BASE_ADDRESS, DTCM_RAM_SIZE_KB*1024);
+#endif
+
+    /*
+      create a DMA reserve heap, to ensure we keep some memory for DMA
+      safe memory allocations
+     */
+    void *dma_reserve = malloc_dtcm(DMA_RESERVE_SIZE);
+    if (!dma_reserve) {
+        dma_reserve = chHeapAllocAligned(NULL, DMA_RESERVE_SIZE, MIN_ALIGNMENT);
+    }
+    chHeapObjectInit(&dma_reserve_heap, dma_reserve, DMA_RESERVE_SIZE);
+}
+
 void *malloc_ccm(size_t size)
 {
     void *p = NULL;
 #if defined(CCM_RAM_SIZE_KB)
-    if (!ccm_heap_initialised) {
-        ccm_heap_initialised = true;
-        chHeapObjectInit(&ccm_heap, (void *)CCM_BASE_ADDRESS, CCM_RAM_SIZE_KB*1024);
-    }
     p = chHeapAllocAligned(&ccm_heap, size, CH_HEAP_ALIGNMENT);
     if (p != NULL) {
         memset(p, 0, size);
@@ -67,21 +94,17 @@ void *malloc_ccm(size_t size)
     return p;
 }
 
-void *malloc_dtcm(size_t size)
+static void *malloc_dtcm(size_t size)
 {
     void *p = NULL;
 #if defined(DTCM_RAM_SIZE_KB)
-    if (!dtcm_heap_initialised) {
-        dtcm_heap_initialised = true;
-        chHeapObjectInit(&dtcm_heap, (void *)DTCM_BASE_ADDRESS, DTCM_RAM_SIZE_KB*1024);
-    }
     p = chHeapAllocAligned(&dtcm_heap, size, CH_HEAP_ALIGNMENT);
-    if (p != NULL) {
-        memset(p, 0, size);
-    }
 #else
     (void)size;
 #endif
+    if (p != NULL) {
+        memset(p, 0, size);
+    }
     return p;
 }
 
@@ -109,24 +132,36 @@ void *malloc(size_t size)
             return p;
         }
     }
+
+    // fall back to DMA reserve
+    p = chHeapAllocAligned(&dma_reserve_heap, size, MIN_ALIGNMENT);
+    if (p) {
+        memset(p, 0, size);
+        return p;
+    }
+
     return NULL;
 }
 
 /*
-  allocte DMA-safe memory
+  allocate DMA-safe memory
  */
 void *malloc_dma(size_t size)
 {
+    void *p;
 #if defined(DTCM_RAM_SIZE_KB)
-    return malloc_dtcm(size);
+    p = malloc_dtcm(size);
 #else
     // if we don't have DTCM memory then assume that main heap is DMA-safe
-    void *p = chHeapAllocAligned(NULL, size, MIN_ALIGNMENT);
+    p = chHeapAllocAligned(NULL, size, MIN_ALIGNMENT);
+#endif
+    if (p == NULL) {
+        p = chHeapAllocAligned(&dma_reserve_heap, size, MIN_ALIGNMENT);
+    }
     if (p) {
         memset(p, 0, size);
     }
     return p;
-#endif
 }
 
 void *calloc(size_t nmemb, size_t size)
@@ -165,6 +200,10 @@ size_t mem_available(void)
     totalp += dtcm_available;
 #endif
 
+    size_t reserve_available = 0;
+    chHeapStatus(&dma_reserve_heap, &reserve_available, NULL);
+    totalp += reserve_available;
+
     return totalp;
 }
 

libraries/AP_HAL_ChibiOS/hwdef/common/stm32_util.h

@@ -31,7 +31,6 @@ void show_stack_usage(void);
 // allocation functions in malloc.c    
 size_t mem_available(void);
 void *malloc_ccm(size_t size);
-void *malloc_dtcm(size_t size);
 void *malloc_dma(size_t size);
 
 // flush all dcache
@@ -68,6 +67,9 @@ void set_fast_reboot(enum rtc_boot_magic v);
 // enable peripheral power if needed
 void peripheral_power_enable(void);
 
+// initialise allocation subsystem
+void malloc_init(void);
+    
 #ifdef __cplusplus
 }
 #endif