78 lines
2.0 KiB
C
78 lines
2.0 KiB
C
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/*
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* (C) Copyright 2004
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* Wolfgang Denk, DENX Software Engineering, wd@denx.de.
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*
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* See file CREDITS for list of people who contributed to this
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* project.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of
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* the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
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* MA 02111-1307 USA
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*/
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/*
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* Check memory range for valid RAM. A simple memory test determines
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* the actually available RAM size between addresses `base' and
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* `base + maxsize'.
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*/
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long get_ram_size(volatile long *base, long maxsize)
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{
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volatile long *addr;
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long save[32];
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long cnt;
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long val;
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long size;
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int i = 0;
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for (cnt = (maxsize / sizeof (long)) >> 1; cnt > 0; cnt >>= 1) {
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addr = base + cnt; /* pointer arith! */
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save[i++] = *addr;
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*addr = ~cnt;
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}
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addr = base;
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save[i] = *addr;
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*addr = 0;
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if ((val = *addr) != 0) {
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/* Restore the original data before leaving the function.
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*/
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*addr = save[i];
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for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {
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addr = base + cnt;
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*addr = save[--i];
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}
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return (0);
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}
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for (cnt = 1; cnt < maxsize / sizeof (long); cnt <<= 1) {
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addr = base + cnt; /* pointer arith! */
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val = *addr;
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*addr = save[--i];
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if (val != ~cnt) {
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size = cnt * sizeof (long);
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/* Restore the original data before leaving the function.
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*/
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for (cnt <<= 1; cnt < maxsize / sizeof (long); cnt <<= 1) {
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addr = base + cnt;
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*addr = save[--i];
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}
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return (size);
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}
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}
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return (maxsize);
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}
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