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/* crt0.S. C design runtime startup file.

   Copyright (C) 2004, Jacob Bower
   Copyright (C) 2010, Embecosm Limited <info@embecosm.com>
   Copyright (C) 2011, ORSoC AB

   Contributor Jeremy Bennett <jeremy.bennett@embecosm.com>
   Contributor Julius Baxter  <julius.baxter@orsoc.se>

   This file is part of Newlib.

   The original work by Jacob Bower is provided as-is without any kind of
   warranty. Use it at your own risk!

   All subsequent work is bound by version 3 of the GPL as follows.

   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 3 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, see <http://www.gnu.org/licenses/>.            */
/* -------------------------------------------------------------------------- */
/* This program is commented throughout in a fashion suitable for processing
   with Doxygen.                                                              */
/* -------------------------------------------------------------------------- */

#include "spr-defs.h"

/* -------------------------------------------------------------------------- */
/*!Macro to load a symbol's address into a register.         
  
  @param[in] gpr  General purpose register to load address into.       
  @param[in] symbol Name of symbol to load.                                   */
/* -------------------------------------------------------------------------- */
#define LOAD_SYMBOL_2_GPR(gpr,symbol)  \
        .global symbol ;               \
        l.movhi gpr, hi(symbol) ;      \
        l.ori   gpr, gpr, lo(symbol)

/* -------------------------------------------------------------------------- */
/*!Macro to handle exceptions.                               

  Load NPC into r3, EPCR into r4
                                                                              */
/* -------------------------------------------------------------------------- */
// Size of redzone + size of space required to store state
// This value must match that in the support library or1k_exception_handler
// function
#define EXCEPTION_STACK_SIZE (128+128)
        
#define CALL_EXCEPTION_HANDLER                          \
        l.addi  r1, r1, -EXCEPTION_STACK_SIZE;          \
        l.sw    4(r1), r3;                              \
        l.sw    8(r1), r4;                              \
        l.mfspr r3,r0,SPR_NPC;                          \
        l.j     or1k_exception_handler;                 \
        l.mfspr r4,r0,SPR_EPCR_BASE

/* -------------------------------------------------------------------------- */
/*!Exception vectors                                                          */
/* -------------------------------------------------------------------------- */
        .section .vectors,"ax"

        /* 0x100: RESET exception */
        .org    0x100   
__reset:
        l.movhi r0, 0
        l.movhi r1, 0
        l.movhi r2, 0
        l.movhi r3, 0
        l.movhi r4, 0
        l.movhi r5, 0
        l.movhi r6, 0
        l.movhi r7, 0
        l.movhi r8, 0
        l.movhi r9, 0
        l.movhi r10, 0
        l.movhi r11, 0
        l.movhi r12, 0
        l.movhi r13, 0
        l.movhi r14, 0
        l.movhi r15, 0
        l.movhi r16, 0
        l.movhi r17, 0
        l.movhi r18, 0
        l.movhi r19, 0
        l.movhi r20, 0
        l.movhi r21, 0
        l.movhi r22, 0
        l.movhi r23, 0
        l.movhi r24, 0
        l.movhi r25, 0
        l.movhi r26, 0
        l.movhi r27, 0
        l.movhi r28, 0
        l.movhi r29, 0
        l.movhi r30, 0
        l.movhi r31, 0

        /* Clear status register, set supervisor mode */
        l.ori r1, r0, SPR_SR_SM
        l.mtspr r0, r1, SPR_SR
        /* Clear timer mode register*/
        l.mtspr r0, r0, SPR_TTMR
        /* Jump to program initialisation code */
        LOAD_SYMBOL_2_GPR(r4, _start)
        l.jr    r4
        l.nop

        .org    0x200
        CALL_EXCEPTION_HANDLER

        /* 0x300: Data Page Fault exception */
        .org    0x300
        CALL_EXCEPTION_HANDLER
        
        /* 0x400: Insn Page Fault exception */
        .org    0x400
        CALL_EXCEPTION_HANDLER

        /* 0x500: Timer exception */
        .org    0x500
        CALL_EXCEPTION_HANDLER

        /* 0x600: Aligment exception */
        .org    0x600
        CALL_EXCEPTION_HANDLER
        
        /* 0x700: Illegal insn exception */
        .org    0x700
        CALL_EXCEPTION_HANDLER

        /* 0x800: External interrupt exception */
        .org    0x800
        CALL_EXCEPTION_HANDLER

        /* 0x900: DTLB miss exception */
        .org    0x900
        CALL_EXCEPTION_HANDLER
        
        /* 0xa00: ITLB miss exception */
        .org    0xa00
        CALL_EXCEPTION_HANDLER
        
        /* 0xb00: Range exception */
        .org    0xb00
        CALL_EXCEPTION_HANDLER
        
        /* 0xc00: Syscall exception */
        .org    0xc00
        CALL_EXCEPTION_HANDLER
        
        /* 0xd00: floating point exception */
        .org    0xd00
        CALL_EXCEPTION_HANDLER
        
        /* 0xe00: Trap exception */
        .org    0xe00
        CALL_EXCEPTION_HANDLER
        
        /* 0xf00: Reserved exceptions */
        .org    0xf00
        CALL_EXCEPTION_HANDLER
        
        .org    0x1000
        CALL_EXCEPTION_HANDLER
        
        .org    0x1100
        CALL_EXCEPTION_HANDLER
        
        .org    0x1200
        CALL_EXCEPTION_HANDLER
        
        .org    0x1300
        CALL_EXCEPTION_HANDLER
        
        .org    0x1400
        CALL_EXCEPTION_HANDLER
        
        .org    0x1500
        CALL_EXCEPTION_HANDLER
        
        .org    0x1600
        CALL_EXCEPTION_HANDLER
        
        .org    0x1700
        CALL_EXCEPTION_HANDLER
        
        .org    0x1800
        CALL_EXCEPTION_HANDLER
        
        .org    0x1900
        CALL_EXCEPTION_HANDLER
        
        .org    0x1a00
        CALL_EXCEPTION_HANDLER
        
        .org    0x1b00
        CALL_EXCEPTION_HANDLER
        
        .org    0x1c00
        CALL_EXCEPTION_HANDLER
        
        .org    0x1d00
        CALL_EXCEPTION_HANDLER
        
        .org    0x1e00
        CALL_EXCEPTION_HANDLER
        
        .org    0x1f00
        CALL_EXCEPTION_HANDLER

        /* Pad to the end */
        .org    0x1ffc
        l.nop

/* -------------------------------------------------------------------------- */
/*!Main entry point
  
   We initialise the stack and frame pointer first, before we set up the
   caches, since otherwise we'll need to disable the instruction cache when
   patching the bus error vector code.

   The remaining tasks are then:
   - optionally set up instruction and/or data caches
   - clear BSS
   - call global and static constructors
   - set up destructors to be called from exit
   - jump to the main function
   - call exit if the main function ever returns.
   - loop forever (should never get here)                                     */
/* -------------------------------------------------------------------------- */
        /* The stack grows down from the top of writable memory. */
        .section .data
        .global stack
stack:  .space  4,0     

        .section .text
        .global _start
        .type   _start,@function


        /* Following externs from board-specific object passed at link time */
        .extern _board_mem_base
        .extern _board_mem_size
        .extern _board_uart_base
        
_start:
        /* Initialise stack and frame pointer (set to same value) */
        l.movhi r1,hi(_board_mem_base)
        l.ori   r1,r1,lo(_board_mem_base)
        l.lwz   r1,0(r1)
        l.movhi r2,hi(_board_mem_size)
        l.ori   r2,r2,lo(_board_mem_size)
        l.lwz   r2,0(r2)
        l.add   r1,r1,r2
        l.or    r2,r1,r1

        /* Store stack address in stack variable */
        l.movhi r3,hi(stack)
        l.ori   r3,r3,lo(stack)
        l.sw    0(r3),r1
        
        /* Initialise cache */
        /* TODO - potentially make this optional for simulation targets to save
        time during startup */
        l.jal   or1k_cache_init
        l.nop
        
        /* Clear BSS */
.L10:   l.movhi r3,hi(__bss_start)
        l.ori   r3,r3,lo(__bss_start)
        l.movhi r4,hi(end)
        l.ori   r4,r4,lo(end)

.L1:    l.sw    (0)(r3),r0
        l.sfltu r3,r4
        l.bf    .L1
        l.addi  r3,r3,4         /* Delay slot */

        /* Reinitialize the reentrancy structure */
        l.jal   __impure_init
        l.nop

        /* Call global and static constructors */
        l.jal   __init
        l.nop
        
        /* Set up destructors to be called from exit if main ever returns */
        l.movhi r3,hi(__fini)
        l.jal   atexit
        l.ori   r3,r3,lo(__fini)        /* Delay slot */

        /* Check if UART is to be initialised */
        l.movhi r4,hi(_board_uart_base)
        l.ori   r4,r4,lo(_board_uart_base)
        l.lwz   r4,0(r4)
        l.sfne  r4,r0           /* Is base set? If not, no UART */
        l.bnf   .L2
        l.or    r3,r0,r0
        l.jal   __uart_init
        l.nop

.L2:    
        /* Jump to main program entry point (argc = argv = envp = 0) */
        l.or    r3,r0,r0
        l.or    r4,r0,r0
        l.jal   main
        l.or    r5,r0,r0                /* Delay slot */

        /* If program exits, call exit routine */
        l.jal   exit
        l.addi  r3,r11,0                /* Delay slot */

        /* Loop forever */
.L3:    l.j     .L3
        l.nop
        
        .size   _start, .-_start