rm48x50: VFP lazy stacking

You need to turn on RT_VFP_LAZY_STACKING in rtconfig.h. By default, RTT
will turn on VFP for all threads and stack all the VFP registers. When
doing lazy stacking, VFP will only be turned on for the thread who
issued VFP instructions.

Currently, if a thread turned on VFP, it cannot be turned off. RTT will
never know what time the thread doesn't need VFP any more. The thread
might could turn off the VFP for it self in proper time.

bsp/rm48x50/HALCoGen/source/sys_core.asm

@@ -72,8 +72,8 @@ _coreInitRegisters_
         orr   r2,      r2,         #0xF00000
         mcr   p15,     #0x00,      r2,       c1, c0, #0x02
 
-        ; Enable FPV
-        fmrx  R2,      fpexc
+        .if (RT_VFP_LAZY_STACKING) = 0
+        fmrx  r2,      fpexc
         orr   r2,      r2,   #0x40000000
         fmxr  fpexc,   r2
 
@@ -93,6 +93,7 @@ _coreInitRegisters_
         fmdrr d13,        r1,     r1
         fmdrr d14,        r1,     r1
         fmdrr d15,        r1,     r1
+        .endif
         bl    next1
 next1
         bl    next2

bsp/rm48x50/HALCoGen/source/sys_intvecs.asm

@@ -21,8 +21,7 @@
 
 resetEntry
         b   _c_int00
-undefEntry
-        b   undefEntry
+        b   turnon_VFP
 svcEntry
         b   svcEntry
 prefetchEntry
@@ -33,5 +32,13 @@ reservedEntry
         b   IRQ_Handler
         ldr pc,[pc,#-0x1b0]
 
-    
+    .sect ".text"
+turnon_VFP
+        ; Enable FPV
+        STMDB sp!,     {r0}
+        fmrx  r0,      fpexc
+        orr   r0,      r0,   #0x40000000
+        fmxr  fpexc,   r0
+        LDMIA sp!,     {r0}
+        subs  pc,      lr,   #4
 ;-------------------------------------------------------------------------------

bsp/rm48x50/rtconfig.h

@@ -211,6 +211,7 @@
 // #define RTGUI_USING_MOUSE_CURSOR
 // </section>
 
+#define RT_VFP_LAZY_STACKING
 // </RDTConfigurator>
 
 #endif