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  */
get_ram_size(long * base,long maxsize)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 
get_effective_memsize(void)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