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发表于 2014-9-11 18:55:41
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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:
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* Check memory range for valid RAM. A simple memory test determines0 p$ M& v, Y3 y" i* @
* the actually available RAM size between addresses `base' and- R6 D0 i+ v* z! C! P
* `base + maxsize'.
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long get_ram_size(long *base, long maxsize)
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volatile long *addr;9 B6 h& ^- V9 e, H6 F' l
long save[32];
/ F6 C: p$ e; i j3 ]: A long cnt;
* o" K; {( i4 {0 A long val;
9 t& x7 L% M# X, W% W3 o long size;
# C7 ^7 ?5 K7 ?; J/ e. e int i = 0;: w6 e6 A. T+ ^, v {, [
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for (cnt = (maxsize / sizeof (long)) >> 1; cnt > 0; cnt >>= 1) {
, f4 `% ~4 ?/ ^: U4 H addr = base + cnt; /* pointer arith! */
5 T. d6 B, z$ d- o sync ();. T0 {9 M% A! {' _% q2 P |' L
save[i++] = *addr;3 Y1 c! G, \: i3 }+ Y
sync ();
' w2 ?9 V- t4 v* B4 b( R) W: O9 e *addr = ~cnt;$ @! H2 I! n6 b0 l) U4 @
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& ?6 u0 F3 q+ f9 `. t5 `" {& v+ ~ addr = base;
9 z+ H% S6 f1 R3 r- ~ sync ();
, y0 b4 }; l1 x# ~6 G save = *addr;
1 H" d! T( k6 |2 T( D% l4 C sync ();0 G/ d& R" W, G& n$ w
*addr = 0;
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sync ();
1 K8 ?4 I3 I& L( Y0 P if ((val = *addr) != 0) {
1 f8 {. I2 H% F2 Z0 | /* Restore the original data before leaving the function.
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sync ();
; K' B' N+ V: v* j *addr = save;
" L& F( s/ D G1 w) S for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {
2 I' }% o$ D7 i, N# M0 R3 y0 U addr = base + cnt;
% E( V6 j4 s+ {5 q, ?2 I sync ();" w; ~, z# r }) K& n/ [0 Y
*addr = save[--i];) D1 r8 Z; i Q: c
}
# r3 P- V) y- K return (0);, ?0 `5 E* [. j, R
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for (cnt = 1; cnt < maxsize / sizeof (long); cnt <<= 1) {
" q8 T2 u- J/ i% W" r/ q addr = base + cnt; /* pointer arith! *// p7 V- {5 S# W: a2 M5 ]9 R! e
val = *addr;5 i B$ \& @0 y$ }+ U
*addr = save[--i];2 n' Y5 a- { s' u( r, g
if (val != ~cnt) {( J" u; d6 w% o" H3 e |) A7 B# m; i
size = cnt * sizeof (long);
, Q* U0 n/ u* e6 }5 @ /* Restore the original data before leaving the function.* v; u+ K) [# v) }5 f( D# @
*/
) b5 R* n& F9 W/ p# } for (cnt <<= 1; cnt < maxsize / sizeof (long); cnt <<= 1) {( N* ^. m/ I2 S9 E" F/ i) F
addr = base + cnt;
$ H& m# T9 j1 V" F" {; n& `3 ^ *addr = save[--i];+ ]2 J. U7 v) Y1 j
}
' v% w- L7 q( T5 w1 H return (size);
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return (maxsize);9 |6 c$ B8 W) \+ q" U' L0 x
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int dram_init(void)
+ f, c7 z6 t! l: r; Y; k9 k{
# H3 O1 \# N+ g$ F2 q( C+ p /* dram_init must store complete ramsize in gd->ram_size */
( j6 ^' N5 V7 W/ E% e! ^3 m gd->ram_size = get_ram_size(: W% M& T7 Q" h
(void *)CONFIG_SYS_SDRAM_BASE,* B& o3 M( ]% U3 j8 v
CONFIG_MAX_RAM_BANK_SIZE);* Q6 U) a5 C4 e$ Q" G/ N1 H2 Z
return 0;
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u, K* G8 }7 J6 }, QFLASH是通过检查FLASH内部的ID识别容量,希望对您有帮助!4 O7 J+ z: N7 p+ s H% E( R' w7 g
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