Added FAST_RAM_INITIALIZED (#5733)

* Added FAST_RAM_INITIALIZED for those who really want it

* Added the white crow of KISSFCV2F7

* Made initialized data LMAs robust

* Fixed indirection when initializing fast memory

src/main/fc/fc_init.c

@@ -265,10 +265,18 @@ void init(void)
 {
 #ifdef USE_ITCM_RAM
     /* Load functions into ITCM RAM */
-    extern unsigned char tcm_code_start;
+    extern uint8_t tcm_code_start;
-    extern unsigned char tcm_code_end;
+    extern uint8_t tcm_code_end;
-    extern unsigned char tcm_code;
+    extern uint8_t tcm_code;
-    memcpy(&tcm_code_start, &tcm_code, (int)(&tcm_code_end - &tcm_code_start));
+    memcpy(&tcm_code_start, &tcm_code, (size_t) (&tcm_code_end - &tcm_code_start));
+#endif
+
+#ifdef USE_FAST_RAM
+    /* Load FAST_RAM_INITIALIZED variable intializers into FAST RAM */
+    extern uint8_t _sfastram_data;
+    extern uint8_t _efastram_data;
+    extern uint8_t _sfastram_idata;
+    memcpy(&_sfastram_data, &_sfastram_idata, (size_t) (&_efastram_data - &_sfastram_data));
 #endif
 
 #ifdef USE_HAL_DRIVER

src/main/flight/pid.c

@@ -158,7 +158,7 @@ void pidResetITerm(void)
     }
 }
 
-static FAST_RAM float itermAccelerator = 1.0f;
+static FAST_RAM_INITIALIZED float itermAccelerator = 1.0f;
 
 void pidSetItermAccelerator(float newItermAccelerator)
 {

src/main/target/KISSFCV2F7/stm32_flash_f722_no_split.ld

@@ -136,7 +136,7 @@ SECTIONS
   } >FLASH
 
   /* used by the startup to initialize data */
-  _sidata = .;
+  _sidata = LOADADDR(.data);
 
   /* Initialized data sections goes into RAM, load LMA copy after code */
   .data :
@@ -182,6 +182,21 @@ SECTIONS
     __sram2_end__ = _esram2;
   } >SRAM2
 
+  /* used during startup to initialized fastram_data */
+  _sfastram_idata = LOADADDR(.fastram_data);
+
+  /* Initialized FAST_RAM section for unsuspecting developers */
+  .fastram_data :
+  {
+    . = ALIGN(4);
+    _sfastram_data = .;        /* create a global symbol at data start */
+    *(.fastram_data)           /* .data sections */
+    *(.fastram_data*)          /* .data* sections */
+
+    . = ALIGN(4);
+    _efastram_data = .;        /* define a global symbol at data end */
+  } >FASTRAM AT> FLASH
+
   . = ALIGN(4);
   .fastram_bss (NOLOAD) :
   {

src/main/target/common_fc_pre.h

@@ -99,8 +99,10 @@
 
 #ifdef USE_FAST_RAM
 #define FAST_RAM                    __attribute__ ((section(".fastram_bss"), aligned(4)))
+#define FAST_RAM_INITIALIZED        __attribute__ ((section(".fastram_data"), aligned(4)))
 #else
 #define FAST_RAM
+#define FAST_RAM_INITIALIZED
 #endif // USE_FAST_RAM
 
 #ifdef STM32F4

src/main/target/link/stm32_flash_f7_split.ld

@@ -93,7 +93,7 @@ SECTIONS
   } >FLASH AT >AXIM_FLASH
 
   /* used by the startup to initialize data */
-  _sidata = .;
+  _sidata = LOADADDR(.data);
 
   /* Initialized data sections goes into RAM, load LMA copy after code */
   .data :
@@ -139,6 +139,21 @@ SECTIONS
     __sram2_end__ = _esram2;
   } >SRAM2
 
+  /* used during startup to initialized fastram_data */
+  _sfastram_idata = LOADADDR(.fastram_data);
+
+  /* Initialized FAST_RAM section for unsuspecting developers */
+  .fastram_data :
+  {
+    . = ALIGN(4);
+    _sfastram_data = .;        /* create a global symbol at data start */
+    *(.fastram_data)           /* .data sections */
+    *(.fastram_data*)          /* .data* sections */
+
+    . = ALIGN(4);
+    _efastram_data = .;        /* define a global symbol at data end */
+  } >FASTRAM AT> FLASH
+
   . = ALIGN(4);
   .fastram_bss (NOLOAD) :
   {

src/main/target/link/stm32_flash_split.ld

@@ -106,7 +106,7 @@ SECTIONS
   } >FLASH
 
   /* used by the startup to initialize data */
-  _sidata = .;
+  _sidata = LOADADDR(.data);
 
   /* Initialized data sections goes into RAM, load LMA copy after code */
   .data :
@@ -136,6 +136,22 @@ SECTIONS
     __bss_end__ = _ebss;
   } >RAM
 
+  /* used during startup to initialized fastram_data */
+  _sfastram_idata = LOADADDR(.fastram_data);
+
+  /* Initialized FAST_RAM section for unsuspecting developers */
+  .fastram_data :
+  {
+    . = ALIGN(4);
+    _sfastram_data = .;        /* create a global symbol at data start */
+    *(.fastram_data)           /* .data sections */
+    *(.fastram_data*)          /* .data* sections */
+
+    . = ALIGN(4);
+    _efastram_data = .;        /* define a global symbol at data end */
+  } >FASTRAM AT> FLASH
+
+  . = ALIGN(4);
   .fastram_bss (NOLOAD) :
   {
     __fastram_bss_start__ = .;