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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:5 n% o( W0 Y& x$ ?* t6 L9 o, h
/*
1 z, `, y% g3 ]; _" ]9 G* Check memory range for valid RAM. A simple memory test determines
f1 G. H" E: _' o5 c* the actually available RAM size between addresses `base' and# u0 V. b* B6 v, H
* `base + maxsize'.5 A; w* T' i, j4 U
*/
! O4 n( ^) O2 |long get_ram_size(long *base, long maxsize)
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0 u7 w) l ]1 S! z0 Q; T1 Y* R' ~ volatile long *addr;* n3 X4 I6 d4 j
long save[32];3 s. d, V/ c* F7 c
long cnt;
( n) @7 z& _/ E' i long val;
1 O5 Q% c: u% f! K5 X, H+ } long size;: y0 O" ~$ U( t" v( [- C7 N1 g$ R3 M
int i = 0;/ z" _! M$ t+ s+ ?
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for (cnt = (maxsize / sizeof (long)) >> 1; cnt > 0; cnt >>= 1) {
! M& [- }( n. A" `; [4 q addr = base + cnt; /* pointer arith! */
9 b& t# I3 j$ o* T sync ();- ^- J0 y1 J4 ]9 g# E7 h
save[i++] = *addr;6 x$ e/ C4 H( n9 J, E
sync ();$ y( y9 \/ V; X! b+ \( x: t2 F1 [
*addr = ~cnt;7 q; x1 y9 s s9 r; d% W
}
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addr = base;
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save = *addr;7 {0 u4 e3 i* g" k- |7 W
sync ();
+ N+ f; H% C. l& k( [; \ *addr = 0;/ B6 y |; s1 |7 i4 ~$ Z# b2 k
0 Y# l3 A$ ]' C" a sync ();
) {$ R3 e) O- L+ G if ((val = *addr) != 0) {
; B3 y5 e' U* e* D! K& ]9 a /* Restore the original data before leaving the function.
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sync ();
@5 [3 z3 z, ? *addr = save;
# G, S- p% f' D; z5 Y for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {! {2 N) h0 F# ^
addr = base + cnt;( y* \( y7 M( V. j- i! n$ Q
sync ();
: u W% s% h! D *addr = save[--i];
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return (0);7 D, a/ f1 i% R/ z( q+ E
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' M% o) f* x7 S& q/ h* H; T for (cnt = 1; cnt < maxsize / sizeof (long); cnt <<= 1) {
4 X$ o( E& K O5 E( O8 q/ O8 U" Z addr = base + cnt; /* pointer arith! */
- f7 R+ k$ e3 F5 l5 A9 Q6 w/ ` val = *addr;: N1 B! k" C5 k6 G
*addr = save[--i];% y* j, u" R; C
if (val != ~cnt) {
0 D% m: ?, D+ d! }* c size = cnt * sizeof (long);
' X2 h3 z* q. U. y! I" Q6 W /* Restore the original data before leaving the function.% m8 Z/ ]8 e* O8 P
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for (cnt <<= 1; cnt < maxsize / sizeof (long); cnt <<= 1) {& H- i! f& N2 m) c
addr = base + cnt;+ `6 X7 G7 B: U- G5 K
*addr = save[--i];
% }. B6 r5 `+ r- V4 z3 Q. j. t }
# [+ ]& c1 N, G) P7 y return (size);
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} [4 |0 D# f Y# X3 o
1 H+ n" [1 E- d8 {; F) x return (maxsize);0 J. D# }0 f! F
}
- ?. R: Q2 d4 \/ D0 J+ {; vint dram_init(void)+ s" V( @* E- y! E s T
{
3 _( V. c8 N0 j+ z5 n' F3 P /* dram_init must store complete ramsize in gd->ram_size */
, [* t `* t& d% c gd->ram_size = get_ram_size(; B/ C. Z0 K: u4 O! N- i
(void *)CONFIG_SYS_SDRAM_BASE,
3 C* J5 P: e* J# n CONFIG_MAX_RAM_BANK_SIZE);* Y& Q: J' ]$ o7 j# L/ v$ m# j5 R/ n
return 0;
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$ \2 r( B. s" oFLASH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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