NIOS II/f core

Altera_Forum · ‎09-11-2004

I create system design based on NIOS II/s core (insrt cahe 512 bytes).

In my design programm and data memory located in SRAM (Cyc. dev board). RESET and ISR code in on_chip RAM.

My program work correctly (instr. cashe not used).

When I replace NIOS II/s to NIOS II/f core my programm start work incorrectly (not work lwip stack).

What reason for this behavior?

Altera_Forum · ‎09-11-2004

The are two potential reasons why your Nios II/f fails.

There is a known bug in the Nios II/f data cache in release 1.0 that shows up on Cyclone.

A fix for this bug will be released in a few weeks with the Nios II 1.0.1 release.

The bug is a rare case that only shows up in unoptimized code. So, as a quick experiment,

make sure all your code is compiled with optimization enabled.

The other possibility is that the data cache isn't being bypassed/flushed consistently by the software.

The Nios II/f uses a writeback cache so if software bypasses the data cache on a store and

then uses a normal load that reads the value from the data cache, the most-recent value

of that address won't be returned. This is not a bug in the data cache but is a bug in the software.

Can you tell me more about your SOPC Builder system and the software you are running?

Altera_Forum · ‎09-12-2004

//------------------------------------------------------

Quartus design: VHDL full_featured

System libtrary: 1C20_full (altera full_featured design), single thread

Design compiler: Quartus 4.1 SP1

Fitter settings:

Physical synthesis effort: NORMAL

Perform physical synthesis for combinational logic = checked

Perform register duplication = cheked

Perform register retiming = cheked

Application: catted stand alone lwIP WEB server (removed all application calls), lwipopts.h by default.

Test task: checking PING function

//------------------------------------------------------

Test options:

Linker: all memory place to ext_ram.

Optimization(NONE):

lib: -O0

app: -O0

Data cashe: 2KByte - passed

Data cashe:

1KByte - failed ( printf ("Application started.\n"); executed. )

1KByte(Set compiler options for lib & app to: -O3, -faster code) - failed.

1KByte(as prev., rwdata placed to SDRAM) - failed.

//------------------------------------------------------

In the main code data cashe memory dirrectly not used!!!

int main(void)
{
    struct netif netif;
    struct ip_addr ipaddr, netmask, gw;
    unsigned int now, lasttime;
    int i;# if IP_REASSEMBLY
    int j;# endif
  alt_avalon_lan91c111_if* dev_list_ptr =  (alt_avalon_lan91c111_if*)alt_ethernet_device_list.next;
    printf("Example web server using Light-weight IP (LWIP)\n");
    printf("and simple RAM-based file system.\n\n");
/* Initialize lwip */
    lwip_init();
    printf ("Setting IP address to: %d.%d.%d.%d\n", IPADDR0, IPADDR1, IPADDR2, IPADDR3);
    printf ("Setting netmask to: %d.%d.%d.%d\n", NETMASK0, NETMASK1, NETMASK2, NETMASK3);
    printf ("Setting gateway address to: %d.%d.%d.%d\n", GWADDR0, GWADDR1, GWADDR2, GWADDR3);
    IP4_ADDR(&ipaddr, IPADDR0, IPADDR1, IPADDR2, IPADDR3);
    IP4_ADDR(&netmask, NETMASK0, NETMASK1, NETMASK2, NETMASK3);
    IP4_ADDR(&gw, GWADDR0, GWADDR1, GWADDR2, GWADDR3);
   netif_add(&netif, &ipaddr, &netmask, &gw,
                                          (void*)dev_list_ptr,
                                          lan91c111if_init, 
                                          ip_input);
    netif_set_default(&netif);
    
/*Initialize application(s) */
/*
 * main loop to service the Ethernet device and expire TCP timers
 */
  printf ("Application started.\n");
  lasttime = get_milliseconds();
  
    i=0;# if IP_REASSEMBLY
    j=0;# endif
    while(1)
    {
  lan91c111if_service(&netif);
  
  now = get_milliseconds();
  if (now - lasttime > TCP_TMR_INTERVAL) {
      lasttime = now;
      tcp_tmr();
      if (++i==50) { /*etharp_tmr();*/ i=0;    }    
  }
# if IP_REASSEMBLY
      if (++j==1000) { ip_reass_timer(); j=0; }    # endif
  
    }
}

Any comments?

Altera_Forum · ‎09-13-2004

Don't forget to make things like this:

alt_avalon_lan91c111_if* dev_list_ptr = (alt_avalon_lan91c111_if*)alt_ethernet_device_list.next;

volatile declerations (volatile doesn't bypass cache anymore, but it should be done still since the compiler could synthesize that out).