source: rtems/bsps/i386/pc386/start/bspgetworkarea.c @ 9964895

/*
 *  This routine is an implementation of the bsp_work_area_initialize()
 *  that can be used by all m68k BSPs following linkcmds conventions
 *  regarding heap, stack, and workspace allocation.
 *
 *  COPYRIGHT (c) 1989-2008.
 *  On-Line Applications Research Corporation (OAR).
 *
 *  The license and distribution terms for this file may be
 *  found in the file LICENSE in this distribution or at
 *  http://www.rtems.org/license/LICENSE.
 */

/* #define BSP_GET_WORK_AREA_DEBUG */
#include <bsp.h>
#include <bsp/bootcard.h>

#ifdef BSP_GET_WORK_AREA_DEBUG
  #include <rtems/bspIo.h>
#endif

/*
 *  These are provided by the linkcmds.
 */
extern char   WorkAreaBase[];
extern char   HeapSize[];
extern char   RamSize[];

/* rudimentary multiboot info */
struct multiboot_info {
  uint32_t  flags;       /* start.S only raises flags for items actually */
                         /* saved; this allows us to check for the size  */
                         /* of the data structure.                       */
  uint32_t  mem_lower;  /* avail kB in lower memory */
  uint32_t  mem_upper;  /* avail kB in lower memory */
  /* ... (unimplemented) */
};

extern struct multiboot_info _boot_multiboot_info;

/*
 *  This is the first address of the memory we can use for the RTEMS
 *  Work Area.
 */ 
static uintptr_t rtemsWorkAreaStart;

/*
 * Board's memory size easily be overridden by application.
 */
uint32_t bsp_mem_size = 0;

/* Size of stack used during initialization. Defined in 'start.s'.  */
extern uint32_t _stack_size;

static void bsp_size_memory(void)
{
  uintptr_t topAddr;

  /* Set the value of start of free memory. */
  rtemsWorkAreaStart = (uint32_t)WorkAreaBase + _stack_size;

  /* Align the RTEMS Work Area at beginning of free memory. */
  if (rtemsWorkAreaStart & (CPU_ALIGNMENT - 1))  /* not aligned => align it */
    rtemsWorkAreaStart = (rtemsWorkAreaStart+CPU_ALIGNMENT) & ~(CPU_ALIGNMENT-1);

  /* The memory detection algorithm is very crude; try
   * to use multiboot info, if possible (set from start.S)
   */
  if ( ((uintptr_t)RamSize == (uintptr_t) 0xFFFFFFFF)  &&
       (_boot_multiboot_info.flags & 1) &&
       _boot_multiboot_info.mem_upper ) {
    topAddr = _boot_multiboot_info.mem_upper * 1024;
    #ifdef BSP_GET_WORK_AREA_DEBUG
      printk( "Multiboot info says we have 0x%08x\n", topAddr );
    #endif
  } else if ( (uintptr_t) RamSize == (uintptr_t) 0xFFFFFFFF ) {
    uintptr_t lowest;
    uint32_t  val;
    int       i;

    /*
     * We have to dynamically size memory. Memory size can be anything
     * between no less than 2M and 2048M.  If we can write a value to
     * an address and read the same value back, then the memory is there.
     *
     * WARNING: This can detect memory which should be reserved for
     *          graphics controllers which share the CPU's RAM.
     */

    /* find the lowest 1M boundary to probe */
    lowest = ((rtemsWorkAreaStart + (1<<20)) >> 20) + 1;
    if ( lowest  < 2 )
      lowest = 2;

    for (i=2048; i>=lowest; i--) {
      topAddr = i*1024*1024 - 4;
      *(volatile uint32_t*)topAddr = topAddr;
    }

    for(i=lowest; i<=2048; i++) {
      topAddr = i*1024*1024 - 4;
      val =  *(volatile uint32_t*)topAddr;
      if (val != topAddr) {
        break;
      }
    }

    topAddr = (i-1)*1024*1024;
    #ifdef BSP_GET_WORK_AREA_DEBUG
      printk( "Dynamically sized to 0x%08x\n", topAddr );
    #endif
  } else {
    topAddr = (uintptr_t) RamSize;
    #ifdef BSP_GET_WORK_AREA_DEBUG
      printk( "hardcoded to 0x%08x\n", topAddr );
    #endif
  }

  bsp_mem_size = topAddr;
}

void bsp_work_area_initialize(void)
{
  void *area_start;
  uintptr_t area_size;

  /*
   *  We need to determine how much memory there is in the system.
   */
  bsp_size_memory();

  area_start = (void *) rtemsWorkAreaStart;
  area_size  = (uintptr_t) bsp_mem_size - (uintptr_t) rtemsWorkAreaStart;
  bsp_work_area_initialize_default( area_start, area_size );
}