# X# f. M: k. D% O4 ?# J/ @) b, i作者: 2532609929 时间: 2014-9-11 18:55
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： $ r7 n w4 J% q4 R7 x& w/* H& H8 b/ ]7 p! o+ I0 h* Check memory range for valid RAM. A simple memory test determines / f3 S7 ~4 H) k s, i: V; [4 `0 Y* the actually available RAM size between addresses `base' and 6 ]8 A# g L+ [* `base + maxsize'.+ ^: n Q* D; B
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long get_ram_size(long *base, long maxsize) 8 _: Q6 b) x; w: D3 A{# C& f. c, `# M
volatile long *addr;/ Q! r) Y+ q$ p4 \% t( W5 c7 y) x
long save[32]; " N% U3 n/ ] [0 @" j long cnt;4 d5 w6 `" q* e6 k
long val; + c6 U9 [5 U9 m9 G: x long size; * ]" k8 Q' V* @6 i7 j0 r c int i = 0;8 X0 e! }0 F% ?6 f+ \$ `. s
: M* \0 t% L: Q! X for (cnt = (maxsize / sizeof (long)) >> 1; cnt > 0; cnt >>= 1) { . k2 v/ m4 n) ^5 ~! e4 \* b addr = base + cnt; /* pointer arith! */- _( J5 R/ h( b7 O) y) l! |$ ~
sync (); / ~3 E0 m% D! u) |% J save[i++] = *addr; 3 k/ |. R7 f8 ]0 j2 L) e5 h sync ();+ G: o2 D8 Q: Z3 I2 {* U
*addr = ~cnt; 9 }' I& `$ N5 q! f' i7 H; g B }- X) ?5 f7 w0 |0 f4 w7 g. g1 o
4 [6 S) G' P# b$ P8 p addr = base; ' T: G7 a! R5 V6 g. ~; v" H sync (); }# ]. Y* X& E9 c& D, B# F. O
save = *addr; - W: v) [4 |& W3 F sync ();& m6 i" y3 S0 d, H3 ~" S
*addr = 0;4 R$ W) U! _; P3 b$ i
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sync (); / [3 J& u: m, I2 @! Z+ d l$ O if ((val = *addr) != 0) { & B2 ?7 ]* F1 K ]2 F3 q% U /* Restore the original data before leaving the function.1 v/ }) W8 N4 Q+ m5 v
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sync (); 4 ?; y( s& t n% N& J' s *addr = save;; D* ?9 h0 o8 i9 \
for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {- ~' E$ o% i6 x0 L
addr = base + cnt; t$ l! E& M8 \- E! A sync (); 4 n5 } O5 q+ W" p *addr = save[--i]; % K8 q ^1 V7 a2 M6 X }+ ]6 r2 x- {0 y+ R
return (0); ; l1 A/ J) x5 I( K- a: N5 j } ; y* S/ E7 |, G" @/ }. A1 f; l q2 N" E. q+ W
for (cnt = 1; cnt < maxsize / sizeof (long); cnt <<= 1) { " l2 z* h% w/ Y3 h$ c: Y addr = base + cnt; /* pointer arith! */4 b2 q! i- N7 ], Y J
val = *addr; , h" V7 J7 G+ c& d, X *addr = save[--i]; / @( n$ O* n# ~- y2 [! f! _, G. ^6 g. P if (val != ~cnt) { . d7 \6 I# Q' j$ D2 W2 @ size = cnt * sizeof (long);7 Y. y: B& R) ?7 Z/ [7 X$ O
/* Restore the original data before leaving the function.# ^# [4 R f& o! K6 r9 Q1 ^' P( C; G
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for (cnt <<= 1; cnt < maxsize / sizeof (long); cnt <<= 1) {5 B4 y& X$ \1 Z- ]- Y G
addr = base + cnt;3 Y. x) P: f9 L& w w' _9 F
*addr = save[--i];5 D) a- |. c* x4 v$ K
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return (size); o3 j, i% @6 Z3 C0 e O- U } " K& N; R! `( V$ Z( u. ` }# M/ z( F2 e# W* J) ^
$ _ ?4 K9 d, R$ Z5 E r$ ? return (maxsize); 2 x1 K, X4 ?3 b/ C$ `7 w( N! O}3 {2 f, W4 H% ]( Q: C
int dram_init(void) 7 K( |8 D# ^& n: o# E8 Z) G4 i{6 @$ c e+ @7 n
/* dram_init must store complete ramsize in gd->ram_size */ + Y* F1 I: a% D* L$ k# E gd->ram_size = get_ram_size( , y% m, O5 {' ^# c& s (void *)CONFIG_SYS_SDRAM_BASE, , h Q8 L8 g& _! R/ _ CONFIG_MAX_RAM_BANK_SIZE); ! O# H1 f3 Y0 v2 s( T; T return 0;" q( W, U6 T3 t
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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！ , n, ]/ H2 G2 w- a8 v+ C& s1 a+ s
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