xref: /openbmc/u-boot/common/memsize.c (revision ceeee8f7)
1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * (C) Copyright 2004
4  * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
5  */
6 
7 #include <common.h>
8 
9 DECLARE_GLOBAL_DATA_PTR;
10 
11 #ifdef __PPC__
12 /*
13  * At least on G2 PowerPC cores, sequential accesses to non-existent
14  * memory must be synchronized.
15  */
16 # include <asm/io.h>	/* for sync() */
17 #else
18 # define sync()		/* nothing */
19 #endif
20 
21 /*
22  * Check memory range for valid RAM. A simple memory test determines
23  * the actually available RAM size between addresses `base' and
24  * `base + maxsize'.
25  */
26 long get_ram_size(long *base, long maxsize)
27 {
28 	volatile long *addr;
29 	long           save[BITS_PER_LONG - 1];
30 	long           save_base;
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_base = *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 		*base = save_base;
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 			/* warning: don't restore save_base in this case,
80 			 * it is already done in the loop because
81 			 * base and base+size share the same physical memory
82 			 * and *base is saved after *(base+size) modification
83 			 * in first loop
84 			 */
85 			return (size);
86 		}
87 	}
88 	*base = save_base;
89 
90 	return (maxsize);
91 }
92 
93 phys_size_t __weak get_effective_memsize(void)
94 {
95 #ifndef CONFIG_VERY_BIG_RAM
96 	return gd->ram_size;
97 #else
98 	/* limit stack to what we can reasonable map */
99 	return ((gd->ram_size > CONFIG_MAX_MEM_MAPPED) ?
100 		CONFIG_MAX_MEM_MAPPED : gd->ram_size);
101 #endif
102 }
103