// SPDX-License-Identifier: GPL-2.0+

  /*
   * (C) Copyright 2004
   * Wolfgang Denk, DENX Software Engineering, wd@denx.de.

   */

  #include <common.h>

  #include <init.h>

  
  DECLARE_GLOBAL_DATA_PTR;

  #ifdef __PPC__
  /*
   * At least on G2 PowerPC cores, sequential accesses to non-existent
   * memory must be synchronized.
   */
  # include <asm/io.h>	/* for sync() */
  #else
  # define sync()		/* nothing */
  #endif

  
  /*
   * Check memory range for valid RAM. A simple memory test determines
   * the actually available RAM size between addresses `base' and
   * `base + maxsize'.
   */

  long get_ram_size(long *base, long maxsize)

  {
  	volatile long *addr;

  	long           save[BITS_PER_LONG - 1];

  	long           save_base;

  	long           cnt;
  	long           val;
  	long           size;
  	int            i = 0;

  	for (cnt = (maxsize / sizeof(long)) >> 1; cnt > 0; cnt >>= 1) {

  		addr = base + cnt;	/* pointer arith! */

  		sync();

  		save[i++] = *addr;

  		sync();

  		*addr = ~cnt;

  	}

  	addr = base;
  	sync();

  	save_base = *addr;

  	sync();
  	*addr = 0;

  	sync();

  	if ((val = *addr) != 0) {
  		/* Restore the original data before leaving the function. */
  		sync();

  		*base = save_base;

  		for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {
  			addr  = base + cnt;
  			sync();
  			*addr = save[--i];
  		}
  		return (0);
  	}
  
  	for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {

  		addr = base + cnt;	/* pointer arith! */
  		val = *addr;

  		*addr = save[--i];
  		if (val != ~cnt) {

  			size = cnt * sizeof(long);
  			/*
  			 * Restore the original data
  			 * before leaving the function.

  			 */

  			for (cnt <<= 1;
  			     cnt < maxsize / sizeof(long);
  			     cnt <<= 1) {

  				addr  = base + cnt;

  				*addr = save[--i];

  			}

  			/* warning: don't restore save_base in this case,
  			 * it is already done in the loop because
  			 * base and base+size share the same physical memory
  			 * and *base is saved after *(base+size) modification
  			 * in first loop
  			 */

  			return (size);
  		}

  	}

  	*base = save_base;

  
  	return (maxsize);
  }

  
  phys_size_t __weak get_effective_memsize(void)
  {
  #ifndef CONFIG_VERY_BIG_RAM
  	return gd->ram_size;
  #else
  	/* limit stack to what we can reasonable map */
  	return ((gd->ram_size > CONFIG_MAX_MEM_MAPPED) ?
  		CONFIG_MAX_MEM_MAPPED : gd->ram_size);
  #endif
  }