F3 - Add support for code in CCM RAM.

src/link/stm32_flash.ld

@@ -53,6 +53,19 @@ SECTIONS
     _etext = .;        /* define a global symbols at end of code */
   } >FLASH
 
+  /* Critical program code goes into CCM RAM */
+  /* Copy specific fast-executing code to CCM RAM */ 
+  ccm_code = LOADADDR(.ccm_code); 
+  .ccm_code :
+  {
+    . = ALIGN(4);
+    ccm_code_start = .; 
+    *(.ccm_code)
+    *(.ccm_code*)
+    . = ALIGN(4);
+    ccm_code_end = .; 
+  } >CCM AT >FLASH
+
 
    .ARM.extab   : { *(.ARM.extab* .gnu.linkonce.armextab.*) } >FLASH
     .ARM : {

src/main/drivers/system.c

@@ -253,6 +253,14 @@ void initialiseMemorySections(void)
     memcpy(&tcm_code_start, &tcm_code, (size_t) (&tcm_code_end - &tcm_code_start));
 #endif
 
+#ifdef USE_CCM_CODE
+    /* Load functions into RAM */
+    extern uint8_t ccm_code_start;
+    extern uint8_t ccm_code_end;
+    extern uint8_t ccm_code;
+    memcpy(&ccm_code_start, &ccm_code, (size_t) (&ccm_code_end - &ccm_code_start));
+#endif
+
 #ifdef USE_FAST_RAM
     /* Load FAST_RAM variable intializers into DTCM RAM */
     extern uint8_t _sfastram_data;

src/main/target/common_pre.h

@@ -44,6 +44,7 @@
 #define MINIMAL_CLI
 #define USE_DSHOT
 #define USE_GYRO_DATA_ANALYSE
+#define USE_CCM_CODE
 #endif
 
 #ifdef STM32F4
@@ -133,6 +134,7 @@
 #define DEFAULT_AUX_CHANNEL_COUNT       6
 #endif
 
+
 #ifdef USE_ITCM_RAM
 #define FAST_CODE                   __attribute__((section(".tcm_code")))
 #define FAST_CODE_NOINLINE          NOINLINE
@@ -141,6 +143,12 @@
 #define FAST_CODE_NOINLINE
 #endif // USE_ITCM_RAM
 
+#ifdef USE_CCM_CODE
+#define CCM_CODE              __attribute__((section(".ccm_code")))
+#else
+#define CCM_CODE
+#endif
+
 #ifdef USE_FAST_RAM
 #define FAST_RAM_ZERO_INIT             __attribute__ ((section(".fastram_bss"), aligned(4)))
 #define FAST_RAM                    __attribute__ ((section(".fastram_data"), aligned(4)))