i have used volatile & register, but gcc still insists upon this
Ilya Enkovich wrote:
>
> Hi,
>
> Do you use 'volatile' type qualifier to prevent undesirable
> transformations of FPGA registers reading code?
>
> BR
> Ilya
>
> 2011/8/1 andy_code <andy_code@xxxxxxxxxx>:
>>
>> hi,
>>
>> I have a function I wrote that part of a keypad reading interrupt for an
>> embbed os we have written for coldfire processors
>> in this function the code reads an FPGA that controls the interrupt, it
>> should only read it once any more and
>> it would confuse the FPGA.
>>
>> here is the original function
>>
>> void keypad_isr(void)
>> {
>> /* read a character from the key buffer */
>> FPGA_UART_DATA *ptr;
>> FPGA_UART_DATA kpd;
>> int g;
>> int n;
>> KEYBUFFER *kb;
>> char ch;
>>
>> kb = &key_buffer;
>> asm(" halt"); /* just for debugging */
>> ptr = FPGA_UART; /* make a pointer to the FPGA register */
>> // read upto 8 keys from the keypad
>> for( n = 0; n < 8 ; n++ )
>> {
>> kpd = *ptr; /* read from register (only do this ONCE)
>> */
>> g = kpd.fifo_cnt;
>> if(g == 0)
>> return;
>> ch = (char) kpd.rx_data;
>> kb->status = ch;
>> if( ch != 0 && ch != -1 )
>> {
>> if ( kb->current_location >= MAX_KEY_BUFFERS_SIZE-1 )
>> {
>> kb->current_location = MAX_KEY_BUFFERS_SIZE-1;
>> }
>> kb->key_buff[kb->current_location] = ch;
>> kb->current_location++;
>> }
>> }
>> }
>>
>> ok now here is my problem, gcc does not use an address register for the
>> pointer, and it insists on reading the FPGA directly twice ????
>> here is generated assembly from gcc.
>>
>> keypad_isr:
>> lea (-12,%sp),%sp
>> movem.l #1036,(%sp)
>> move.w -1073741664,%d0 <<<--- should use %a0 surely
>> clr.l %d1
>> move.w %d0,%d1 <<< --- theres the read
>> moveq #13,%d2
>> lsr.l %d2,%d1
>> tst.b %d1
>> jeq .L3
>> moveq #8,%d1
>> lea key_buffer+33,%a1
>> lea key_buffer,%a0
>> lea key_buffer+1,%a2
>> jra .L5
>> .L8:
>> move.w -1073741664,%d0 <<< --- look its done it again ?????
>> clr.l %d2
>> move.w %d0,%d2 <<< --- ARRRGGGgg its knackered my
>> FPGA
>> moveq #13,%d3
>> lsr.l %d3,%d2
>> tst.b %d2
>> jeq .L3
>> .L5:
>> move.b %d0,%d2
>> move.b %d0,(%a1)
>> move.l %d2,%d0
>> addq.l #1,%d0
>> and.l #255,%d0
>> moveq #1,%d3
>> cmp.l %d0,%d3
>> jcc .L6
>> clr.l %d0
>> move.b (%a0),%d0
>> move.b #30,%d3
>> cmp.l %d0,%d3
>> jcc .L7
>> move.b #31,(%a0)
>> .L7:
>> move.b (%a0),%d0
>> clr.l %d3
>> move.b %d0,%d3
>> move.b %d2,(%a2,%d3.l)
>> addq.l #1,%d0
>> move.b %d0,(%a0)
>> .L6:
>> subq.l #1,%d1
>> jne .L8
>> .L3:
>> movem.l (%sp),#1036
>> lea (12,%sp),%sp
>> rts
>>
>> ok how do i stop this happening, thats not the code I wrote.
>> please help, I is tearing my hair out
>>
>> thank you
>> --
>> View this message in context:
>> http://old.nabble.com/gcc-4.6.1-messes-up-code----why-tp32169196p32169196.html
>> Sent from the gcc - Help mailing list archive at Nabble.com.
>>
>>
>
>
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