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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:) f9 O! k. d& \ K3 _2 u
/*
; J7 O; K) | F. K6 O- k* Check memory range for valid RAM. A simple memory test determines* [; O+ I/ B) f* @$ i% x( q& n0 M9 ~6 b
* the actually available RAM size between addresses `base' and }% ]2 ] ^$ u, }+ ?3 h% {
* `base + maxsize'., J9 i+ y Y0 ^+ I% w" g+ j$ D
*/" G9 {: D7 ^: d1 t& h- u+ w3 C
long get_ram_size(long *base, long maxsize)
) e! n& H6 n/ p4 v* Z{
) x9 H& s7 w' k/ ~$ M/ S volatile long *addr;- w6 j- G& O y' x f; J) P, G
long save[32];
9 W3 X x4 Q8 E9 j8 ?1 I, C; Q- ? long cnt;0 k* r }; d4 n+ k% ^! c
long val;
! `7 ]% c% _% N$ T% t: P long size;
0 Q& v& J7 Z' H& t( y8 E; l int i = 0;
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% z# q9 c! f2 v: P* t( H for (cnt = (maxsize / sizeof (long)) >> 1; cnt > 0; cnt >>= 1) {
8 f7 x6 Y9 b P+ c/ s addr = base + cnt; /* pointer arith! */
9 ]+ a+ b4 {$ z+ w; P$ t, _ sync ();8 C' T- [8 t7 N% ]
save[i++] = *addr;- F, F9 A+ d- e2 l; u* t A- M' L
sync ();
5 K. n4 {; K" D( a7 m *addr = ~cnt;
" {5 X7 N7 s5 Z }
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1 t5 _3 z- S2 P/ j* i; w& `# w& c! P addr = base;" c6 j, b) ^, s7 {2 M
sync ();
: Q7 {4 p2 \. c* i D+ j+ z save = *addr;
% T5 H9 s% l" h7 w" u& e' {* y* h sync ();- ?1 O- [! _* R# A
*addr = 0;0 h. ?8 k$ p" `. n. J
+ p: R$ ?) Z6 S5 ^1 j {- H sync ();
8 q6 m0 N- ]0 c8 g+ B5 E if ((val = *addr) != 0) {& {& y/ ]$ y; P- v
/* Restore the original data before leaving the function.5 Z1 ?7 \# t, ^; Q5 w
*/
4 H0 I$ X0 @0 u5 x z: T0 `& o sync ();3 k$ x% [. v0 W2 w2 I1 r( B% d
*addr = save;( h; O5 I" O7 k% u+ s$ h7 _, P5 O
for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {
" K9 ~# ^- x- f$ o/ p" | addr = base + cnt;' Y1 S" K+ M8 `* H8 ]; o
sync ();
- _# s8 [ Q+ O( u* V: N) i *addr = save[--i];* x0 T6 ]5 g9 E: X0 Y
}
! a6 c4 v0 i, c return (0);5 V! h. E% [1 ^+ H( V
}; K6 [4 g# Q) @- I6 N# Q
" s, i+ e5 p, W
for (cnt = 1; cnt < maxsize / sizeof (long); cnt <<= 1) {% B! _9 ^+ G( \1 x
addr = base + cnt; /* pointer arith! */
0 P: m0 M: W9 z8 }( ]% B# ~2 c0 n* U+ x val = *addr;! G6 p' T6 a0 R: g
*addr = save[--i];
5 a& Q# o/ J! k( w if (val != ~cnt) {
4 ^3 e' H# ^* U K& P" r W0 D6 m. F size = cnt * sizeof (long);
, C) C* T/ h4 C /* Restore the original data before leaving the function.
1 m8 X* `. ?+ P$ p+ S7 w- J0 ^ */" J( Q# ~3 n! h# N- G- H
for (cnt <<= 1; cnt < maxsize / sizeof (long); cnt <<= 1) {2 l0 X+ O( J! f
addr = base + cnt;
0 ^& K+ f- T' K *addr = save[--i]; X S [; e: t! g8 {5 |
}# M9 g1 B4 L0 c% ?% i% C; c$ f
return (size);! t2 W3 b/ e4 ], @
}
- n/ d/ j% r6 n8 G/ a: n- m- j! { }
" W! T8 X( k# Z
$ N: H! G- l' r0 t3 W8 P return (maxsize);8 d" m5 |1 C5 j/ k% l E- _0 }
}! ]* {) ~! s! a; Z8 @' d( L) w1 x! Z
int dram_init(void)
, V$ G! z, T. e- p{
; a8 V$ E1 g" t7 w( h /* dram_init must store complete ramsize in gd->ram_size */
8 _& t0 o w# L gd->ram_size = get_ram_size(/ g2 U3 X% a {' X! H$ A, E. t: f
(void *)CONFIG_SYS_SDRAM_BASE,! ]" g! c; q$ N/ _9 v
CONFIG_MAX_RAM_BANK_SIZE);
' l( q: e6 M) w- m9 T return 0;1 q' b+ G' [4 L$ [' R
}& Y8 m Z, M1 O' h: m6 R0 o+ \$ `
" I3 f/ X k! x8 G' n
" N% S2 I# w! M: q) b' r
4 \/ ?8 C) y6 v
* j3 d& G! g) t' L) ]% g' c( @
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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