NWRAM & Direct Boot (#1149)

* SCFG_BIOS now selects between NDS and DSi BIOS
Allowing experimental direct boot.

* - making NWRAM Priorities work as in the HW
- fixed loading DSi stage2 Bootloader when in direct boot (should not be loaded) and might interfere with the image loaded into the (N)WRAM previously

* NWRAM and SCFG Registers are now write-guarded by the corresponding SCFG_EXT7/9 Bits

* removed debugging remainder

* Moved NDSHeader dependent SCFG initialization into the new DSi::SetupDirectBoot function called from NDS::SetupDirectBoot when ConsoleType is DSi

* removed redundant SCFG_BIOS bit checks

* Set of changes from RSDuck's review

* removed a forgotten comment

* - removed the guarded debug outputs for NWRAM
- NWRAM writes to bank and window registers now apply their write masks.
- added comment on an existing TODO within the code describing, why this is OK
- fixed initial NWRAM bank reset just accessing set A

* NWRAM not mapped to 03... range if bit25 in SCFG_EXT is cleared

* removed NWRAM write block on cleared bit25 in SCFG_EXT

* changed type of iterator for MapNWRAM_x functions from s8 to int

* - reduced calculations/comparisons on NWRAM write operations
- changed u8 to unsigned int for an iterator MapNWRAM_x

Co-authored-by: Tim Seidel <t.seidel@kts-systeme.de>

src/DSi.h

@@ -60,6 +60,7 @@ bool Init();
 void DeInit();
 void Reset();
 
+void SetupDirectBoot();
 void SoftReset();
 
 bool LoadBIOS();

src/NDS.cpp

@@ -164,7 +164,6 @@ bool Running;
 
 bool RunningGame;
 
-
 void DivDone(u32 param);
 void SqrtDone(u32 param);
 void RunTimer(u32 tid, s32 cycles);
@@ -342,8 +341,13 @@ void SetupDirectBoot()
 {
     if (ConsoleType == 1)
     {
-        printf("!! DIRECT BOOT NOT SUPPORTED IN DSI MODE\n");
-        return;
+        // With the BIOS select in SCFG_BIOS and the initialization od
+        // SCFG_BIOS depending on the Header->UnitType, we can now boot 
+        // directly in the roms.
+        // There are some more SCFG Settings that change depending on
+        // the unit type, so this is experimental
+        printf("!! DIRECT BOOT NOT STABLE IN DSI MODE\n");
+        DSi::SetupDirectBoot();
     }
 
     u32 bootparams[8];