Use saved mstatus for FPU/VPU state determination

portable/GCC/RISC-V/chip_specific_extensions/Pulpino_Vega_RV32M1RM/freertos_risc_v_chip_specific_extensions.h

@@ -80,22 +80,22 @@ csrr t2, lpcount0
 csrr t3, lpstart1
 csrr t4, lpend1
 csrr t5, lpcount1
-sw t0, 2 * portWORD_SIZE( sp )
-sw t1, 3 * portWORD_SIZE( sp )
-sw t2, 4 * portWORD_SIZE( sp )
-sw t3, 5 * portWORD_SIZE( sp )
-sw t4, 6 * portWORD_SIZE( sp )
-sw t5, 7 * portWORD_SIZE( sp )
+sw t0, 1 * portWORD_SIZE( sp )
+sw t1, 2 * portWORD_SIZE( sp )
+sw t2, 3 * portWORD_SIZE( sp )
+sw t3, 4 * portWORD_SIZE( sp )
+sw t4, 5 * portWORD_SIZE( sp )
+sw t5, 6 * portWORD_SIZE( sp )
    .endm
 
 /* Restore the additional registers found on the Pulpino. */
    .macro portasmRESTORE_ADDITIONAL_REGISTERS
-lw t0, 2 * portWORD_SIZE( sp ) /* Load additional registers into accessible temporary registers. */
-lw t1, 3 * portWORD_SIZE( sp )
-lw t2, 4 * portWORD_SIZE( sp )
-lw t3, 5 * portWORD_SIZE( sp )
-lw t4, 6 * portWORD_SIZE( sp )
-lw t5, 7 * portWORD_SIZE( sp )
+lw t0, 1 * portWORD_SIZE( sp ) /* Load additional registers into accessible temporary registers. */
+lw t1, 2 * portWORD_SIZE( sp )
+lw t2, 3 * portWORD_SIZE( sp )
+lw t3, 4 * portWORD_SIZE( sp )
+lw t4, 5 * portWORD_SIZE( sp )
+lw t5, 6 * portWORD_SIZE( sp )
 csrw lpstart0, t0
 csrw lpend0, t1
 csrw lpcount0, t2

portable/GCC/RISC-V/portASM.S

@@ -193,8 +193,8 @@ definitions. */
  * portTASK_RETURN_ADDRESS
  * [FPU registers (when enabled/available) go here]
  * [VPU registers (when enabled/available) go here]
- * [chip specific registers go here]
  * mstatus
+ * [chip specific registers go here]
  * pxCode
  */
 pxPortInitialiseStack:
@@ -212,14 +212,6 @@ pxPortInitialiseStack:
     load_x t0, xTaskReturnAddress
     store_x t0, 0(a0)                   /* Return address onto the stack. */
 
-    addi t0, x0, portasmADDITIONAL_CONTEXT_SIZE /* The number of chip specific additional registers. */
-chip_specific_stack_frame:              /* First add any chip specific registers to the stack frame being created. */
-    beq t0, x0, 1f                      /* No more chip specific registers to save. */
-    addi a0, a0, -portWORD_SIZE         /* Make space for chip specific register. */
-    store_x x0, 0(a0)                   /* Give the chip specific register an initial value of zero. */
-    addi t0, t0, -1                     /* Decrement the count of chip specific registers remaining. */
-    j chip_specific_stack_frame         /* Until no more chip specific registers. */
-1:
     csrr t0, mstatus                    /* Obtain current mstatus value. */
     andi t0, t0, ~0x8                   /* Ensure interrupts are disabled when the stack is restored within an ISR.  Required when a task is created after the scheduler has been started, otherwise interrupts would be disabled anyway. */
     addi t1, x0, 0x188                  /* Generate the value 0x1880, which are the MPIE=1 and MPP=M_Mode in mstatus. */
@@ -245,6 +237,15 @@ chip_specific_stack_frame:              /* First add any chip specific registers
     addi a0, a0, -portWORD_SIZE
     store_x t0, 0(a0)                   /* mstatus onto the stack. */
 
+    addi t0, x0, portasmADDITIONAL_CONTEXT_SIZE /* The number of chip specific additional registers. */
+chip_specific_stack_frame:              /* First add any chip specific registers to the stack frame being created. */
+    beq t0, x0, 1f                      /* No more chip specific registers to save. */
+    addi a0, a0, -portWORD_SIZE         /* Make space for chip specific register. */
+    store_x x0, 0(a0)                   /* Give the chip specific register an initial value of zero. */
+    addi t0, t0, -1                     /* Decrement the count of chip specific registers remaining. */
+    j chip_specific_stack_frame         /* Until no more chip specific registers. */
+1:
+
     addi a0, a0, -portWORD_SIZE
     store_x a1, 0(a0)                   /* mret value (pxCode parameter) onto the stack. */
     ret
@@ -256,12 +257,12 @@ xPortStartFirstTask:
 
     load_x  x1, 0( sp ) /* Note for starting the scheduler the exception return address is used as the function return address. */
 
+    portasmRESTORE_ADDITIONAL_REGISTERS /* Defined in freertos_risc_v_chip_specific_extensions.h to restore any registers unique to the RISC-V implementation. */
+
     load_x  x5, 1 * portWORD_SIZE( sp ) /* Initial mstatus into x5 (t0). */
     addi    x5, x5, 0x08                /* Set MIE bit so the first task starts with interrupts enabled - required as returns with ret not eret. */
     csrw    mstatus, x5                 /* Interrupts enabled from here! */
 
-    portasmRESTORE_ADDITIONAL_REGISTERS /* Defined in freertos_risc_v_chip_specific_extensions.h to restore any registers unique to the RISC-V implementation. */
-
     load_x  x7,  5  * portWORD_SIZE( sp )   /* t2 */
     load_x  x8,  6  * portWORD_SIZE( sp )   /* s0/fp */
     load_x  x9,  7  * portWORD_SIZE( sp )   /* s1 */

portable/GCC/RISC-V/portContext.h

@@ -322,17 +322,17 @@ store_x t0, portCRITICAL_NESTING_OFFSET * portWORD_SIZE( sp ) /* Store the criti
     srl t1, t0, MSTATUS_VS_OFFSET
     andi t1, t1, 3
     addi t2, x0, 3
-    bne t1, t2, 2f /* If VPU status is not dirty, do not save FPU registers. */
+    bne t1, t2, 2f /* If VPU status is not dirty, do not save VPU registers. */
 
     portcontexSAVE_VPU_CONTEXT
 2:
 #endif
 
-portasmSAVE_ADDITIONAL_REGISTERS /* Defined in freertos_risc_v_chip_specific_extensions.h to save any registers unique to the RISC-V implementation. */
-
 csrr t0, mstatus
 store_x t0, 1 * portWORD_SIZE( sp )
 
+portasmSAVE_ADDITIONAL_REGISTERS /* Defined in freertos_risc_v_chip_specific_extensions.h to save any registers unique to the RISC-V implementation. */
+
 #if( configENABLE_FPU == 1 )
     /* Mark the FPU as clean, if it was dirty and we saved FPU registers. */
     srl t1, t0, MSTATUS_FS_OFFSET
@@ -396,16 +396,17 @@ load_x sp, 0 ( t1 )     /* Read sp from first TCB member. */
 load_x t0, 0 ( sp )
 csrw mepc, t0
 
-/* Restore mstatus register. */
-load_x t0, 1 * portWORD_SIZE( sp )
-csrw mstatus, t0
-
 /* Defined in freertos_risc_v_chip_specific_extensions.h to restore any registers unique to the RISC-V implementation. */
 portasmRESTORE_ADDITIONAL_REGISTERS
 
+/* Restore mstatus register. It is important to use t3 (and not t0) here as t3
+ * is not clobbered by portcontextRESTORE_VPU_CONTEXT and
+ * portcontextRESTORE_FPU_CONTEXT. */
+load_x t3, 1 * portWORD_SIZE( sp )
+csrw mstatus, t3
+
 #if( configENABLE_VPU == 1 )
-    csrr t0, mstatus
-    srl t1, t0, MSTATUS_VS_OFFSET
+    srl t1, t3, MSTATUS_VS_OFFSET
     andi t1, t1, 3
     addi t2, x0, 3
     bne t1, t2, 5f /* If VPU status is not dirty, do not restore VPU registers. */
@@ -415,8 +416,7 @@ portasmRESTORE_ADDITIONAL_REGISTERS
 #endif /* ifdef portasmSTORE_VPU_CONTEXT */
 
 #if( configENABLE_FPU == 1 )
-    csrr t0, mstatus
-    srl t1, t0, MSTATUS_FS_OFFSET
+    srl t1, t3, MSTATUS_FS_OFFSET
     andi t1, t1, 3
     addi t2, x0, 3
     bne t1, t2, 6f /* If FPU status is not dirty, do not restore FPU registers. */