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//////////////////////////////////////////////////////////////////////
///                                                               //// 
/// bootrom                                                       ////
///                                                               ////
/// Assembly programs to be embedded inside system to aid boot    ////
///                                                               ////
/// Julius Baxter, julius@opencores.org                           ////
///                                                               ////
//////////////////////////////////////////////////////////////////////
////                                                              ////
//// Copyright (C) 2009, 2010 Authors and OPENCORES.ORG           ////
////                                                              ////
//// This source file may be used and distributed without         ////
//// restriction provided that this copyright statement is not    ////
//// removed from the file and that any derivative work contains  ////
//// the original copyright notice and the associated disclaimer. ////
////                                                              ////
//// This source file is free software; you can redistribute it   ////
//// and/or modify it under the terms of the GNU Lesser General   ////
//// Public License as published by the Free Software Foundation; ////
//// either version 2.1 of the License, or (at your option) any   ////
//// later version.                                               ////
////                                                              ////
//// This source 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 Lesser General Public License for more ////
//// details.                                                     ////
////                                                              ////
//// You should have received a copy of the GNU Lesser General    ////
//// Public License along with this source; if not, download it   ////
//// from http://www.opencores.org/lgpl.shtml                     ////
////                                                              ////
//////////////////////////////////////////////////////////////////////

// Defines for which bootrom app to use are in board.h - TODO: use the
// processed orspoc-defines.v file for this define. It makes more sense
// as this software ends up as gates.
        
#include "board.h"

#ifdef BOOTROM_SPI_FLASH
        
        /* Assembly program to go into the boot ROM */
        /* For use with simple_spi SPI master core and standard SPI flash
           interface-compatible parts (ST M25P16 for example.)*/
        /* Currently just loads a program from SPI flash into RAM */
        /* Assuming address at RAM_LOAD_BASE gets clobbered, we need
           a byte writable address somewhere!*/

#define SPI_BASE SPI0_BASE
/* simple_spi driver */ 
#define SPI_SPCR 0x0
#define SPI_SPSR 0x1
#define SPI_SPDR 0x2
#define SPI_SPER 0x3
#define SPI_SPSS 0x4

#define SPI_SPCR_XFER_GO 0x51
#define SPI_SPSS_INIT 0x1
#define SPI_SPSR_RX_CHECK 0x01 /* Check bit 0 is cleared, fifo !empty*/
        
#define RAM_LOAD_BASE SDRAM_BASE
#define RESET_ADDR 0x100

boot_init:      
        l.movhi r0, 0
        l.movhi r1, RAM_LOAD_BASE
        l.movhi r4, hi(SPI_BASE)
        
spi_init:
        l.ori   r2, r0, SPI_SPCR_XFER_GO /* Setup SPCR with enable bit set */
        l.sb    SPI_SPCR(r4), r2
        l.sb    SPI_SPSS(r4), r0         /* Clear SPI slave selects */
        l.ori   r6, r0, SPI_SPSS_INIT
        l.sb    SPI_SPSS(r4), r6         /* Set appropriate slave select */
        l.jal   spi_xfer
        l.ori   r3, r0, 0x3              /* READ command opcode for SPI device*/
        l.jal   spi_xfer
#ifdef BOOTROM_ADDR_BYTE2
        l.ori   r3, r0, BOOTROM_ADDR_BYTE2 /* Use addr if defined. MSB first */
#else   
        l.or    r3, r0, r0
#endif  
        l.jal   spi_xfer
#ifdef BOOTROM_ADDR_BYTE1
        l.ori   r3, r0, BOOTROM_ADDR_BYTE1
#else   
        l.or    r3, r0, r0
#endif  
        l.jal   spi_xfer
#ifdef BOOTROM_ADDR_BYTE0
        l.ori   r3, r0, BOOTROM_ADDR_BYTE0
#else   
        l.or    r3, r0, r0
#endif  
        l.movhi r6, 0
        l.movhi r7, 0xffff      

copy:   
        l.jal   spi_xfer         /* Read a byte into r3 */
        l.add   r8, r1, r6       /* Calculate store address */
        l.sb    0(r8), r3        /* Write byte to memory */
        l.addi  r6, r6, 1        /* Increment counter */
        l.sfeqi r6, 0x4          /* Is this the first word ?*/
        l.bf    store_sizeword   /* put sizeword in the register */
        l.sfeq  r6, r7           /* Check if we've finished loading the words */
        l.bnf   copy             /* Continue copying if not last word */
        l.nop

goto_reset:
        l.ori   r1, r1, RESET_ADDR
        l.jr    r1
        l.sb    SPI_SPSS(r4), r0 /* Clear SPI slave selects */
        
store_sizeword:
#ifdef SPI_RETRY_IF_INSANE_SIZEWORD
        l.lwz   r7, 0(r1)        /* Size word is in first word of SDRAM */
        l.srli  r10, r7, 16      /* Chop the sizeword we read in half */
        l.sfgtui r10, 0x0200     /* It's unlikely we'll ever load > 32MB */
        l.bf    boot_init
        l.nop
        l.j     copy
        l.nop

#else   
        l.j     copy
        l.lwz   r7, 0(r1)         /* Size word is in first word of SDRAM */
#endif
        
spi_xfer:
        l.sb    SPI_SPDR(r4), r3  /* Dummy write what's in r3 */
        l.ori   r3, r0, SPI_SPSR_RX_CHECK /* r3 = , ensure loop just once */
spi_xfer_poll:  
        l.andi  r3, r3, SPI_SPSR_RX_CHECK /* AND read fifo bit empty */
        l.sfeqi r3, SPI_SPSR_RX_CHECK    /* is bit set? ... */
        l.bf    spi_xfer_poll     /* ... if so, rxfifo empty, keep polling */
        l.lbz   r3, SPI_SPSR(r4) /* Read SPSR */
        l.jr    r9
        l.lbz   r3, SPI_SPDR(r4) /* Get data byte */


#endif

#ifdef BOOTROM_GOTO_RESET
        /* Jump to reset vector in the SDRAM */
        l.movhi r0, 0
        l.movhi r4, SDRAM_BASE
        l.ori   r4, r4, 0x100
        l.jr    r4
        l.nop
        
#endif  

#ifdef BOOTROM_LOOP_AT_ZERO

        /* Don't load app via SPI, instead just put an infinite loop into bottom
        of memory and jump there.
        */
        l.movhi r0, 0
        l.movhi r4, SDRAM_BASE
        l.sw    0x0(r4), r0
        l.movhi r5, hi(0x15000001) /* A l.nop 1 so sim exits if this enabled */
        l.ori   r5, r5, lo(0x15000001)
        l.sw    0x4(r4), r5
        l.sw    0x8(r4), r5
        l.sw    0xc(r4), r5
        l.jr    r4
        l.nop

        

#endif

#ifdef BOOTROM_LOOP_IN_ROM

        /* Don't load app via SPI, instead just put an infinite loop into bottom
        of memory and jump there.
        */
        l.movhi r0, 0
        l.nop   0x1
        l.j     0
        l.nop
        l.nop 
#endif