xref: /openbmc/u-boot/common/memsize.c (revision 35546f6f2014282cc4f9772324b5588bd44a2938)
1  /*
2   * (C) Copyright 2004
3   * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4   *
5   * SPDX-License-Identifier:	GPL-2.0+
6   */
7  
8  #include <common.h>
9  
10  DECLARE_GLOBAL_DATA_PTR;
11  
12  #ifdef __PPC__
13  /*
14   * At least on G2 PowerPC cores, sequential accesses to non-existent
15   * memory must be synchronized.
16   */
17  # include <asm/io.h>	/* for sync() */
18  #else
19  # define sync()		/* nothing */
20  #endif
21  
22  /*
23   * Check memory range for valid RAM. A simple memory test determines
24   * the actually available RAM size between addresses `base' and
25   * `base + maxsize'.
26   */
27  long get_ram_size(long *base, long maxsize)
28  {
29  	volatile long *addr;
30  	long           save[32];
31  	long           cnt;
32  	long           val;
33  	long           size;
34  	int            i = 0;
35  
36  	for (cnt = (maxsize / sizeof(long)) >> 1; cnt > 0; cnt >>= 1) {
37  		addr = base + cnt;	/* pointer arith! */
38  		sync();
39  		save[i++] = *addr;
40  		sync();
41  		*addr = ~cnt;
42  	}
43  
44  	addr = base;
45  	sync();
46  	save[i] = *addr;
47  	sync();
48  	*addr = 0;
49  
50  	sync();
51  	if ((val = *addr) != 0) {
52  		/* Restore the original data before leaving the function. */
53  		sync();
54  		*addr = save[i];
55  		for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {
56  			addr  = base + cnt;
57  			sync();
58  			*addr = save[--i];
59  		}
60  		return (0);
61  	}
62  
63  	for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {
64  		addr = base + cnt;	/* pointer arith! */
65  		val = *addr;
66  		*addr = save[--i];
67  		if (val != ~cnt) {
68  			size = cnt * sizeof(long);
69  			/*
70  			 * Restore the original data
71  			 * before leaving the function.
72  			 */
73  			for (cnt <<= 1;
74  			     cnt < maxsize / sizeof(long);
75  			     cnt <<= 1) {
76  				addr  = base + cnt;
77  				*addr = save[--i];
78  			}
79  			return (size);
80  		}
81  	}
82  
83  	return (maxsize);
84  }
85  
86  phys_size_t __weak get_effective_memsize(void)
87  {
88  #ifndef CONFIG_VERY_BIG_RAM
89  	return gd->ram_size;
90  #else
91  	/* limit stack to what we can reasonable map */
92  	return ((gd->ram_size > CONFIG_MAX_MEM_MAPPED) ?
93  		CONFIG_MAX_MEM_MAPPED : gd->ram_size);
94  #endif
95  }
96