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DDR通过检查最大有效地址来识别容量,具体请看uboot的common/memsize.c文件中的检查代码,也可以看如下:7 D% Q+ D# s$ R6 P5 e: G" w
/*2 v2 {$ |3 T3 q, Z0 c
* Check memory range for valid RAM. A simple memory test determines9 p F7 O- Y: x# l
* the actually available RAM size between addresses `base' and
9 c* ~. c5 `- m! A" b' t* `base + maxsize'.+ `1 W; A9 I, U E' M
*/
5 a- ^) s+ n$ `1 @long get_ram_size(long *base, long maxsize)" D9 `4 c% \; j9 U1 C( y! F
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volatile long *addr;
/ S8 i! A8 a) x4 D" I! }+ ~, I long save[32];2 @4 p; a+ _# A7 t
long cnt;
5 H. i- ^1 T2 i0 h long val;4 V! I' v: ~; V5 ^# W
long size;5 S6 K3 S- Q' X+ ?; J m% J
int i = 0;" M* B( ^+ o7 o Y, f
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for (cnt = (maxsize / sizeof (long)) >> 1; cnt > 0; cnt >>= 1) {$ ^3 \7 o" E& o+ [, G1 v
addr = base + cnt; /* pointer arith! */! S$ c( e. c/ v( L+ f
sync ();
9 t2 Z/ z1 U6 v3 n) y save[i++] = *addr;- s& ^+ h3 X7 w T- c
sync ();
& e0 c: c8 X$ ] *addr = ~cnt;
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addr = base;
" ~. n; \+ n6 ^( Z2 J8 N sync ();5 Y+ I! [; ], N' P% ^" Y
save = *addr;! U. `) r# Q2 [! ?$ `
sync ();
: O2 T6 W/ Y5 I) D' y+ Z *addr = 0;. z! j( v6 f; _$ G
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sync ();
- ~0 Q# H/ `. ^ y- _( _" @ if ((val = *addr) != 0) {* j" X h2 @9 B' e+ C
/* Restore the original data before leaving the function.- ]2 \5 N% c% M+ ^4 J
*/
* n7 y/ B7 ^! z sync ();
9 Z. ?* B8 w7 D$ z# S; ?8 a *addr = save;) \9 ?' a) I* ^5 R8 p$ z' {
for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {: a* r. f3 L$ K- d) a0 o" q. _) e
addr = base + cnt;: s9 t0 t# y( I$ {
sync ();
9 C2 k: N% M4 x% o N( _3 o7 B- W *addr = save[--i];
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5 D/ X: l* ~. C: f/ b, K) p& r return (0);* I+ C% L% E* C& g5 \
}
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% [% y/ H3 n! }" V# ]4 o for (cnt = 1; cnt < maxsize / sizeof (long); cnt <<= 1) {
- b8 n, v7 A; S8 f; y addr = base + cnt; /* pointer arith! */4 D( x/ R- C0 a: t- M- r. _$ O s* }
val = *addr;/ C4 G H* B' ~: n; Z3 X8 M
*addr = save[--i];1 X' p+ W" d2 n6 ]6 u P
if (val != ~cnt) {
$ K2 _/ ]9 T0 P8 G# ` size = cnt * sizeof (long);1 b m3 P# d' o
/* Restore the original data before leaving the function.* U( A+ C, z8 ]; ~
*/
1 \! \7 }1 T9 V6 X for (cnt <<= 1; cnt < maxsize / sizeof (long); cnt <<= 1) {
3 I" Y8 c( p6 m$ J( |2 k addr = base + cnt;% Q$ T0 g S5 m8 e) E
*addr = save[--i];
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return (size);$ {# z) l: p, C" R9 x- p% E- w
}
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return (maxsize);
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# g3 j. G" @: \int dram_init(void)
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/* dram_init must store complete ramsize in gd->ram_size */
8 R }2 U9 e: S; u( [ gd->ram_size = get_ram_size(& u' o1 W# S" D$ Y) h0 a
(void *)CONFIG_SYS_SDRAM_BASE,, o0 s. U8 H" a# X
CONFIG_MAX_RAM_BANK_SIZE);/ r2 ~) c4 ?4 h+ m* b3 I! H6 X! X% N
return 0; b% r7 j/ Q- ]! w$ ]
}
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FLASH是通过检查FLASH内部的ID识别容量,希望对您有帮助!
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