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/*
----------------------------------------------------------------------
    CHiPES Embedded RTR Systems Copyright (c) Tim Oliver 2002-2004
----------------------------------------------------------------------
 File   : os_cpu_a.S
 Author(s) :    Tim Oliver, timtimoliver@yahoo.co.uk
                Julius Baxter, julius@opencores.org
---------------------------[Description]------------------------------
        Start up file for OpenRISC Reference Platform
        Assembly code required for ORP port of MicroC/OS-II 
        
        Macros :
         exception_vector name org
                load32i reg const
                store_context
                restore_context
        
        Internal Routines :
                _reset          Boot code installed at interrupt vector 0x100
                _start          Start up sequence

                _OSTickISR      Operating system timer tick interrupt service routine
                _OSStartHighRdy Starts the highest priority task that is available to run
                _OSCtxSwBP
                _OSCtxSw        Task switch
                _OSIntCtxSw     Task switch after interrupt
                _UserISR        Interrupt service routine template - requires code
                _align          Attempts to recover from memory alignment errors
                nest_not_one
        
        External Routines       :
                _OSIntExit      
                _OSTimeTick
                _OSTaskSwHook
 
        External variables      :
                _OSIntNesting   
                _OSRunning
                _OSPrioHighRdy
                _OSPrioCur
                _OSTCBCur
                _OSTCBHighRdy
        
        Interrupt Vectors Installed:
                0x100   _reset
                0x500   _OSTickISR
                0x600   _align

                0x800   _UserISR

                0xc00   _OSCtxSw
*/

/*
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 
*/

#include "spr-defs.h"
#include "board.h"

#define RED_ZONE_SIZE 128
#define STK_FRAME_SIZE (128+RED_ZONE_SIZE)
#define SPR_TTMR_LOAD  (SPR_TTMR_IE | SPR_TTMR_RT | ((IN_CLK/TICKS_PER_SEC) & SPR_TTMR_PERIOD))

/* function prototypes */

        .global  OSTickISR      /* internal functions */
        .global  OSStartHighRdy
        .global  OSCtxSwBP
        .global  OSCtxSw
        .global  OSIntCtxSw
        .global  UserISR
        .global  _align
        .global  nest_not_one

        .extern  OSIntExit      /* external functions */
        .extern  OSTimeTick
        .extern  OSTaskSwHook

        .extern  OSIntNesting   /* values */
        .extern  OSRunning
        .extern  OSPrioHighRdy
        .extern  OSPrioCur
        .extern  OSTCBCur
        .extern  OSTCBHighRdy

/* Macro Definitions */
/* Utility macro: Load a 32-bit constant into a register */
        .macro  load32i reg const
        l.movhi \reg,hi(\const)
        l.ori   \reg,\reg,lo(\const)
        .endm

/* Utility macro: Start code for an exception handler */
        .macro exception_vector name
        l.addi  r1,r1,-STK_FRAME_SIZE
        l.sw    0xc(r1),r3
        l.movhi r3,hi(\name)
        l.ori   r3,r3,lo(\name)
        l.jr    r3
        l.nop

        .endm

        .macro unhandled_exception
        l.ori r3, r0, 1
        l.j 0
        l.nop NOP_EXIT

        .endm
        
/* Utility macro: store the cpu context on the stack */
        .macro store_context
        l.sw    0x8(r1),r2
        l.sw    0x10(r1),r4
        l.sw    0x14(r1),r5
        l.sw    0x18(r1),r6
        l.sw    0x1c(r1),r7
        l.sw    0x20(r1),r8
        l.sw    0x24(r1),r9
        l.sw    0x28(r1),r10
        l.sw    0x2c(r1),r11
        l.sw    0x30(r1),r12
        l.sw    0x34(r1),r13
        l.sw    0x38(r1),r14
        l.sw    0x3c(r1),r15
        l.sw    0x40(r1),r16
        l.sw    0x44(r1),r17
        l.sw    0x48(r1),r18
        l.sw    0x4c(r1),r19
        l.sw    0x50(r1),r20
        l.sw    0x54(r1),r21
        l.sw    0x58(r1),r22
        l.sw    0x5c(r1),r23
        l.sw    0x60(r1),r24
        l.sw    0x64(r1),r25
        l.sw    0x68(r1),r26
        l.sw    0x6c(r1),r27
        l.sw    0x70(r1),r28
        l.sw    0x74(r1),r29
        l.sw    0x78(r1),r30
        l.sw    0x7c(r1),r31
        .endm

/* Utility macro: restore the cpu context from the stack */
        .macro restore_context
        l.lwz   r2,0x8(r1)
        l.lwz   r3,0xc(r1)
        l.lwz   r4,0x10(r1)
        l.lwz   r5,0x14(r1)
        l.lwz   r6,0x18(r1)
        l.lwz   r7,0x1c(r1)
        l.lwz   r8,0x20(r1)
        l.lwz   r9,0x24(r1)
        l.lwz   r10,0x28(r1)
        l.lwz   r11,0x2c(r1)
        l.lwz   r12,0x30(r1)
        l.lwz   r13,0x34(r1)
        l.lwz   r14,0x38(r1)
        l.lwz   r15,0x3c(r1)
        l.lwz   r16,0x40(r1)
        l.lwz   r17,0x44(r1)
        l.lwz   r18,0x48(r1)
        l.lwz   r19,0x4c(r1)
        l.lwz   r20,0x50(r1)
        l.lwz   r21,0x54(r1)
        l.lwz   r22,0x58(r1)
        l.lwz   r23,0x5c(r1)
        l.lwz   r24,0x60(r1)
        l.lwz   r25,0x64(r1)
        l.lwz   r26,0x68(r1)
        l.lwz   r27,0x6c(r1)
        l.lwz   r28,0x70(r1)
        l.lwz   r29,0x74(r1)
        l.lwz   r30,0x78(r1)
        l.lwz   r31,0x7c(r1)
        .endm

/* actual code */
        
        .section .stack, "aw", @nobits

.space  STACK_SIZE
_stack:

/* Exception vectors */ 

        .section .vectors, "ax"

        .org 0x100
_reset:
        l.movhi r0,0
        l.addi  r3,r0,SPR_SR_SM
        l.mtspr r0,r3,SPR_SR
        load32i r3,_start
        l.jr    r3
        l.nop

        .org 0x200
        unhandled_exception

        .org 0x300
        unhandled_exception

        .org 0x400
        unhandled_exception
        
        .org 0x500
        exception_vector OSTickISR
        
        .org 0x600
        exception_vector _align

        .org 0x700
        unhandled_exception
        
        .org 0x800
        exception_vector UserISR

        .org 0x900
        unhandled_exception

        .org 0xa00
        unhandled_exception

        .org 0xb00
        unhandled_exception

        .org 0xc00
        exception_vector OSCtxSw


        /* Start of text section */
        
        .section .text

        /* _start function - called immediately after reset */
_start:
        
        /* Instruction cache enable */
        /* Check if IC present and skip enabling otherwise */
        l.mfspr r24,r0,SPR_UPR
        l.andi  r26,r24,SPR_UPR_ICP
        l.sfeq  r26,r0
        l.bf    .L8
        l.nop
        
        /* Disable IC */
        l.mfspr r6,r0,SPR_SR
        l.addi  r5,r0,-1
        l.xori  r5,r5,SPR_SR_ICE
        l.and   r5,r6,r5
        l.mtspr r0,r5,SPR_SR
        
        /* Establish cache block size
        If BS=0, 16;
        If BS=1, 32;
        r14 contain block size
        */
        l.mfspr r24,r0,SPR_ICCFGR
        l.andi  r26,r24,SPR_ICCFGR_CBS
        l.srli  r28,r26,7
        l.ori   r30,r0,16
        l.sll   r14,r30,r28
        
        /* Establish number of cache sets
        r16 contains number of cache sets
        r28 contains log(# of cache sets)
        */
        l.andi  r26,r24,SPR_ICCFGR_NCS
        l.srli  r28,r26,3
        l.ori   r30,r0,1
        l.sll   r16,r30,r28
        
        /* Invalidate IC */
        l.addi  r6,r0,0
        l.sll   r5,r14,r28
        
.L7:
        l.mtspr r0,r6,SPR_ICBIR
        l.sfne  r6,r5
        l.bf    .L7
        l.add   r6,r6,r14
        
        /* Enable IC */
        l.mfspr r6,r0,SPR_SR
        l.ori   r6,r6,SPR_SR_ICE
        l.mtspr r0,r6,SPR_SR
        l.nop
        l.nop
        l.nop
        l.nop
        l.nop
        l.nop
        l.nop
        l.nop

.L8:
        /* Data cache enable */
        /* Check if DC present and skip enabling otherwise */
        l.mfspr r24,r0,SPR_UPR
        l.andi  r26,r24,SPR_UPR_DCP
        l.sfeq  r26,r0
        l.bf    .L10
        l.nop
        /* Disable DC */
        l.mfspr r6,r0,SPR_SR
        l.addi  r5,r0,-1
        l.xori  r5,r5,SPR_SR_DCE
        l.and   r5,r6,r5
        l.mtspr r0,r5,SPR_SR
        /* Establish cache block size
           If BS=0, 16;
           If BS=1, 32;
           r14 contain block size
        */
        l.mfspr r24,r0,SPR_DCCFGR
        l.andi  r26,r24,SPR_DCCFGR_CBS
        l.srli  r28,r26,7
        l.ori   r30,r0,16
        l.sll   r14,r30,r28
        /* Establish number of cache sets
           r16 contains number of cache sets
           r28 contains log(# of cache sets)
        */
        l.andi  r26,r24,SPR_DCCFGR_NCS
        l.srli  r28,r26,3
        l.ori   r30,r0,1
        l.sll   r16,r30,r28
        /* Invalidate DC */
        l.addi  r6,r0,0
        l.sll   r5,r14,r28
.L9:
        l.mtspr r0,r6,SPR_DCBIR
        l.sfne  r6,r5
        l.bf    .L9
        l.add   r6,r6,r14
        /* Enable DC */
        l.mfspr r6,r0,SPR_SR
        l.ori   r6,r6,SPR_SR_DCE
        l.mtspr r0,r6,SPR_SR

.L10:

        /* Clear BSS */
        load32i r28, ___bss_start
        load32i r30, __end
1:
        l.sw    (0)(r28), r0
        l.sfltu r28, r30
        l.bf    1b
        l.addi  r28, r28, 4

        /* Initialise stack pointer */
        load32i r1,_stack-4

        l.addi  r2,r0,-3
        l.and   r1,r1,r2
        l.ori   r2,r1,0
        
        load32i r3,main

        l.jr    r3
        l.addi  r3,r0,0


        
_align:
        l.ori   r3,r0,0x600
        l.nop   NOP_REPORT
        l.mfspr r3,r0,SPR_EPCR_BASE
        l.nop   NOP_REPORT
        l.lwz   r3,0(r3)
        l.nop   NOP_REPORT      
        l.mfspr r3,r0,SPR_EEAR_BASE
        l.nop   NOP_REPORT
        /* Loop in place, cause simulator to exit */
        l.ori   r3,r0,1
        l.j     0
        l.nop   NOP_EXIT

/*
------------------------------
            OSCtxSw
------------------------------
 Description :
 This routine switches between two different tasks.
 The task state of one is saved on its kernel stack.
 Then the state of the other is restored from its kernel stack.

 There maybe memory management hardware issues

 Finally, we can return to the second task, via the 'return'.

 Includes OSIntCtxSw
------------------------------
 Uses:
------------------------------
*/

OSCtxSw:
        /* l.sys exception for now so we are in supervisor mode */
        /* exception  - recover pc from epcr */

        l.mfspr r3,r0,SPR_EPCR_BASE     /* save program counter that was put in exception register */
        l.sw    0(r1),r3
        l.mfspr r3,r0,SPR_ESR_BASE      /* save status register that was put in exception register */
        l.sw    4(r1),r3

        store_context
                                        /* Store current stack pointer   */
        load32i r3,OSTCBCur            /* r3= &OSTCBCur */

        l.lwz   r3,0(r3)                /* r3 = &CurrentTask.OSTCBStkPtr  */
        l.sw    0(r3),r1                /* CurrentTask.OSTCBStkPtr = SP */

OSIntCtxSw:
        l.jal   OSTaskSwHook           /* call OSTaskSwHook */
        l.nop

        load32i r2,OSTCBHighRdy        /* r2= &OSTCBHighRdy */
        l.lwz   r2,0(r2)
        load32i r3,OSTCBCur            /* r3= &OSTCBCur */
        l.sw    0(r3),r2                /* OSTCBCur = OSTCBHighRdy */

        load32i r3,OSPrioHighRdy       /* r3= &OSPrioHighRdy */
        l.lbz   r3, 0(r3)
        load32i r4,OSPrioCur           /* r4= &OSPrioCur */
        l.sb    0(r4), r3               /* OSPrioCur = OSPrioHighRdy */

        l.lwz   r1, 0(r2)               /* sp = OSTCBHighRdy */


        l.lwz   r2,0(r1)                /* load context for task to be resumed */
        l.mtspr r0,r2,SPR_EPCR_BASE
        l.lwz   r2,4(r1)
        l.mtspr r0,r2,SPR_ESR_BASE

        restore_context
        
OSCtxSwBP:
        l.addi  r1,r1,STK_FRAME_SIZE
        l.rfe
        l.nop

/*
------------------------------
        OSStartHighRdy
------------------------------
 Description :
   Starts the highest priority task that is available to run

 OSStartHighRdy() MUST:
  a) Call OSTaskSwHook() then,
  b) Set OSRunning to TRUE,
  c) Switch to the HPT

------------------------------
 Uses :
------------------------------
*/
OSStartHighRdy:

        l.jal   OSTaskSwHook           /* call OSTaskSwHook */
        l.nop

        load32i r3,OSRunning           /* r3= &OSRunning */

        l.ori   r4,r0, 0x01             /* set OSRunning == TRUE */
        l.sb    0(r3), r4
                                        /* load stack pointer from next task's TCB area  */
        load32i r3,OSTCBHighRdy        /* r3 = &OSTCBHighRdy */
        l.lwz   r3,0(r3)                /* r3 = &OS_TCB */
        l.lwz   r1, 0(r3)               /* stack is the first element */

        l.lwz   r2,0(r1)
        l.mtspr r0,r2,SPR_EPCR_BASE
        l.lwz   r2,4(r1)
        l.mtspr r0,r2,SPR_ESR_BASE

        restore_context

        l.addi  r1,r1,STK_FRAME_SIZE
        l.rfe
        l.nop

/*
------------------------------
        OSTickISR
------------------------------
 Description :

------------------------------
 Uses :
------------------------------
*/
OSTickISR:
        l.mfspr r3,r0,SPR_EPCR_BASE     /* save program counter that was put in exception register */
        l.sw    0(r1),r3
        l.mfspr r3,r0,SPR_ESR_BASE      /* save status register that was put in exception register */
        l.sw    4(r1),r3

        store_context
/* either call OSIntEnter or Increment OSIntNesting */

/*
        l.jal   OSIntEnter
        l.nop
        load32i r2,OSIntNesting
        l.lbz   r3,0(r2)
*/
        load32i r2,OSIntNesting     /* r2 &OSIntNesting */
        l.lbz   r3,0(r2)             /* r3 OSIntNesting  */
        l.addi  r3,r3,1
        l.sb    0(r2),r3

   /* if (OSIntNesting == 1) OSTCBCur->OSTCBStkPtr = sp */
        l.sfeqi r3,1
        l.bnf   nest_not_one
        l.nop

        load32i r4,OSTCBCur            /* set pointer to Current TCB pointer */
                                        /* r4= &OSTCBCur */

                                        /* Store current stack pointer   */
        l.lwz   r5,0(r4)                /* r5 = &CurrentTask.OSTCBStkPtr  */
        l.sw    0(r5),r1                /* CurrentTask.OSTCBStkPtr = SP */

nest_not_one:
        /* clear interrupt */
        load32i r3,SPR_TTMR_LOAD
        l.mtspr r0,r3,SPR_TTMR

        /* optionally re enable interrupt */

        /*Call OSTimeTick()*/
        l.jal   OSTimeTick
        l.nop
        /*Call OSIntExit()*/
        l.jal   OSIntExit
        l.nop
                                        /* load stack pointer from next task's TCB area  */
        load32i r3,OSTCBHighRdy        /* r3 = &OSTCBHighRdy */
        l.lwz   r3,0(r3)                /* r3 = &OS_TCB */
        l.lwz   r1, 0(r3)               /* stack is the first element */

        l.lwz   r2,0(r1)
        l.mtspr r0,r2,SPR_EPCR_BASE
        l.lwz   r2,4(r1)
        l.mtspr r0,r2,SPR_ESR_BASE

        restore_context

        l.addi  r1,r1,STK_FRAME_SIZE
        l.rfe
        l.nop


        /*
------------------------------
        UserISR
------------------------------
 Description :

------------------------------
 Uses :
------------------------------
*/
UserISR:
        l.mfspr r2,r0,SPR_EPCR_BASE     /* save program counter that was put in exception register */
        l.sw    0(r1),r2
        l.mfspr r2,r0,SPR_ESR_BASE      /* save status register that was put in exception register */
        l.sw    4(r1),r2

        store_context
/* either call OSIntEnter or Increment OSIntNesting */

/*
        l.jal   _OSIntEnter
        l.nop
        load32i r2,_OSIntNesting
        l.lbz   r3,0(r2)
*/
        load32i r2,OSIntNesting     /* r2 &OSIntNesting */

        l.lbz   r3,0(r2)             /* r3 OSIntNesting  */
        l.addi  r3,r3,1
        l.sb    0(r2),r3

   /* if (OSIntNesting == 1) OSTCBCur->OSTCBStkPtr = sp */
        l.sfeqi r3,1
        l.bnf   Unest_not_one
        l.nop

        load32i r4,OSTCBCur            /* set pointer to Current TCB pointer */
                                        /* r4= &OSTCBCur */

                                        /* Store current stack pointer   */
        l.lwz   r5,0(r4)                /* r5 = &CurrentTask.OSTCBStkPtr  */
        l.sw    0(r5),r1                /* CurrentTask.OSTCBStkPtr = SP */

Unest_not_one:
        /* clear interrupt */
        l.mtspr r0,r0,SPR_PICSR

        /* optionally re enable interrupt */

        /*Call interrupt service routine */

        /*Call OSIntExit()*/
        l.jal   OSIntExit
        l.nop

                                        /* load stack pointer from next task's TCB area  */
        load32i r3,OSTCBHighRdy        /* r3 = &OSTCBHighRdy */
        l.lwz   r3,0(r3)                /* r3 = &OS_TCB */
        l.lwz   r1, 0(r3)               /* stack is the first element */

        l.lwz   r2,0(r1)
        l.mtspr r0,r2,SPR_EPCR_BASE
        l.lwz   r2,4(r1)
        l.mtspr r0,r2,SPR_ESR_BASE

        restore_context

        l.addi  r1,r1,STK_FRAME_SIZE
        l.rfe
        l.nop