Dear Wolfgang,
2010/8/8 Wolfgang Denk <[email protected]>:
> Dear [email protected],
> I think this patch is wrong. The value at address (base + 0) is never
> saved, so there is no need to restore it (nor did we store it's value
> anywhere).
The value at base+0 is saved. Please see the following explanation.
long get_ram_size(volatile long *base, long maxsize)
{
volatile long *addr;
long save[32];
long cnt;
long val;
long size;
int i = 0;
for (cnt = (maxsize / sizeof (long)) >> 1; cnt > 0; cnt >>= 1) {
addr = base + cnt; /* pointer arith! */
sync ();
save[i++] = *addr;
sync ();
*addr = ~cnt;
}
addr = base;
sync ();
save[i] = *addr; <----- value of [base+0] is saved.
sync ();
*addr = 0; <----- [base+0] is modified.
sync ();
if ((val = *addr) != 0) {
/* Restore the original data before leaving the function.
*/
sync ();
*addr = save[i]; <----- value of [base+0] is
restored.
for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) {
addr = base + cnt;
sync ();
*addr = save[--i];
}
return (0);
}
+ *addr = save[i]; <----- Therefore we should also restore
[base+0] here.
for (cnt = 1; cnt < maxsize / sizeof (long); cnt <<= 1) {
addr = base + cnt; /* pointer arith! */
val = *addr;
*addr = save[--i];
if (val != ~cnt) {
size = cnt * sizeof (long);
/* Restore the original data before leaving the
function.
*/
for (cnt <<= 1; cnt < maxsize / sizeof (long); cnt <<=
1) {
addr = base + cnt;
*addr = save[--i];
}
return (size);
}
}
return (maxsize);
}
best regards,
Po-Yu Chuang
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