/* * (C) Copyright 2004 * Wolfgang Denk, DENX Software Engineering, wd@denx.de. * * SPDX-License-Identifier: GPL-2.0+ */ #include <config.h> #ifdef __PPC__ /* * At least on G2 PowerPC cores, sequential accesses to non-existent * memory must be synchronized. */ # include <asm/io.h> /* for sync() */ #else # define sync() /* nothing */ #endif /* * Check memory range for valid RAM. A simple memory test determines * the actually available RAM size between addresses `base' and * `base + maxsize'. */ long get_ram_size(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; sync (); *addr = 0; sync (); if ((val = *addr) != 0) { /* Restore the original data before leaving the function. */ sync (); *addr = save[i]; for (cnt = 1; cnt < maxsize / sizeof(long); cnt <<= 1) { addr = base + cnt; sync (); *addr = save[--i]; } return (0); } 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); }