From 24fc6e6ebbb5769941845e4549382be6d6f76ced Mon Sep 17 00:00:00 2001
From: Grissiom <chaos.proton@gmail.com>
Date: Fri, 31 May 2013 20:25:44 +0800
Subject: 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.
---
 libcpu/arm/rm48x50/context_ccs.asm | 12 ++++++------
 libcpu/arm/rm48x50/stack.c         |  9 +++++++--
 2 files changed, 13 insertions(+), 8 deletions(-)

(limited to 'libcpu')

diff --git a/libcpu/arm/rm48x50/context_ccs.asm b/libcpu/arm/rm48x50/context_ccs.asm
index 695844e300..dc4113f5e4 100644
--- a/libcpu/arm/rm48x50/context_ccs.asm
+++ b/libcpu/arm/rm48x50/context_ccs.asm
@@ -75,13 +75,13 @@ __no_vfp_frame1
 
     .if (__TI_VFP_SUPPORT__)
         LDMIA   sp!, {r0}       ; get fpexc
+        VMSR    fpexc,  r0      ; restore fpexc
         TST     r0,  #0x40000000
         BEQ     __no_vfp_frame2
         LDMIA   sp!, {r1}       ; get fpscr
         VMSR    fpscr, r1
 		VLDMIA  sp!, {d0-d15}
 __no_vfp_frame2
-        VMSR    fpexc, r0
     .endif
 
     LDMIA   sp!, {r4}           ; pop new task cpsr to spsr
@@ -99,13 +99,13 @@ rt_hw_context_switch_to
 
     .if (__TI_VFP_SUPPORT__)
         LDMIA   sp!, {r0}       ; get fpexc
+        VMSR    fpexc, r0
         TST     r0,  #0x40000000
         BEQ     __no_vfp_frame_to
         LDMIA   sp!, {r1}       ; get fpscr
         VMSR    fpscr, r1
 		VLDMIA  sp!, {d0-d15}
 __no_vfp_frame_to
-        VMSR    fpexc, r0
     .endif
 
     LDMIA   sp!, {r4}           ; pop new task cpsr to spsr
@@ -162,13 +162,13 @@ __no_vfp_frame_str_irq
 
     .if (__TI_VFP_SUPPORT__)
         LDMIA   sp!, {r0}       ; get fpexc
+        VMSR    fpexc, r0
         TST     r0,  #0x40000000
         BEQ     __no_vfp_frame_ldr_irq
         LDMIA   sp!, {r1}       ; get fpscr
         VMSR    fpscr, r1
 		VLDMIA  sp!, {d0-d15}
 __no_vfp_frame_ldr_irq
-        VMSR    fpexc, r0
     .endif
 
     LDMIA   sp!, {r0-r12,lr}
@@ -184,13 +184,13 @@ rt_hw_context_switch_interrupt_do
 
     .if (__TI_VFP_SUPPORT__)
         LDMIA   sp!, {r0}       ; get fpexc
+        VMSR    fpexc, r0
         TST     r0,  #0x40000000
         BEQ     __no_vfp_frame_do1
         LDMIA   sp!, {r1}       ; get fpscr
         VMSR    fpscr, r1
 		VLDMIA  sp!, {d0-d15}
 __no_vfp_frame_do1
-        VMSR    fpexc, r0
     .endif
 
     LDMIA   sp!, {r0-r12,lr}  ; reload saved registers
@@ -216,7 +216,7 @@ __no_vfp_frame_do1
 		VMRS    r0,  fpexc
         TST     r0,  #0x40000000
         BEQ     __no_vfp_frame_do2
-		VSTMDB  sp!, {d0-d15}
+        VSTMDB  sp!, {d0-d15}
         VMRS    r1, fpscr
         ; TODO: add support for Common VFPv3.
         ;       Save registers like FPINST, FPINST2
@@ -235,13 +235,13 @@ __no_vfp_frame_do2
 
     .if (__TI_VFP_SUPPORT__)
         LDMIA   sp!, {r0}       ; get fpexc
+        VMSR    fpexc, r0
         TST     r0,  #0x40000000
         BEQ     __no_vfp_frame_do3
         LDMIA   sp!, {r1}       ; get fpscr
         VMSR    fpscr, r1
 		VLDMIA  sp!, {d0-d15}
 __no_vfp_frame_do3
-        VMSR    fpexc, r0
     .endif
 
     LDMIA   sp!, {r4}         ; pop new task's cpsr to spsr
diff --git a/libcpu/arm/rm48x50/stack.c b/libcpu/arm/rm48x50/stack.c
index a11d8896f9..02dc84e6f1 100644
--- a/libcpu/arm/rm48x50/stack.c
+++ b/libcpu/arm/rm48x50/stack.c
@@ -58,8 +58,9 @@ rt_uint8_t *rt_hw_stack_init(void *tentry, void *parameter,
 		*(--stk) = SVCMODE;					/* arm mode   */
 
 #ifdef __TI_VFP_SUPPORT__
-    #define VFP_DATA_NR 32
+#ifndef RT_VFP_LAZY_STACKING
     {
+        #define VFP_DATA_NR 32
         int i;
 
         for (i = 0; i < VFP_DATA_NR; i++)
@@ -68,9 +69,13 @@ rt_uint8_t *rt_hw_stack_init(void *tentry, void *parameter,
         }
         /* FPSCR TODO: do we need to set the values other than 0? */
         *(--stk) = 0;
-        /* FPEXC. Enable the FVP by default. */
+        /* FPEXC. Enable the FVP if no lazy stacking. */
         *(--stk) = 0x40000000;
     }
+#else
+        /* FPEXC. Disable the FVP by default. */
+        *(--stk) = 0x00000000;
+#endif
 #endif
 
 	/* return task's current stack address */
-- 
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