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/*
        Register usage
        R0 = 0
        R1 = pointer to destination
        R2 = nr of words to be copied
        R3 = data
        R4 = pointer to SPI core
        R5 = spi control word
        R6 = jump adr
        R7 = nr of control words
        r8 = adr pointer
*/
        .equ spi_base,0xb0000000 ;
        .equ spi_ctrl,0x0520    ; 
        .equ read_cmd, 0x03000000 ;

        .global start           ;
        .text
start:  
        l.movhi r0,0x0          ;
        l.ori r1,r0,0x0 ; # R1 = 0x0
        l.movhi r4,hi(spi_base) ; # R4 = spi base
        l.ori r5,r0,lo(spi_ctrl); # R5 = spi control

        # set SPI regs, can be removed if reset state is changed in IP core
        #l.ori r3,r0,0x420      ;
        #l.sw 0x10(r4),r3       ; # tx at negedge, 32 bit transfer
        #l.movhi r3,0x0300      ;
        #l.ori r3,r3,0x0        ;
        #l.sw 0x0(r4),r3        ; # TX = 0x03000000
        #l.sw 0x14(r4),r0       ; # prescaler to zero
        
        # set slave select active
        l.ori r3,r0,0x1         ; # R3 = 0x1

        # initiate SPI FLASH READ
        l.jal read              ;
        l.sw 0x18(r4),r3        ; # ss active

        # read 
        l.jal read              ;
        l.sw 0x0(r4),r0         ; # set TX to zero
        l.or r2,r3,r3           ; # R2 = nr of words

loop1:  l.jal read              ; # read adr pointer
        l.addi r1,r1,0x8        ;
        l.jal read              ; # read data
        l.or r8,r3,r3           ; # copy adr pointer to r8
        l.sfeq r8,r0            ;
        l.bnf loop1             ;
        l.sw 0x0(r8),r3         ; # write control data
        
loop2:  l.jal read              ;
        l.addi r1,r1,0x4        ;
        l.sw 0x0(r1),r3         ; # write to RAM
        l.sfeq r1,r2            ;
        l.bnf loop2             ;
        l.ori r6,r0,0x100       ;
        l.jr r6                 ;
        # set slave select inactive
        l.sw 0x18(r4),r0        ; # set slave select inactive
        
read:
        l.sw 0x10(r4),r5        ; # write spi control
w4busy: l.lwz r3,0x10(r4)       ;
        l.sfeqi r3,lo(spi_ctrl) ;
        l.bf w4busy             ;
        l.nop                   ; 
        l.jr r9                 ;
        l.lwz r3,0x0(r4)        ; # R3 = RX