| /* |
| * This file is part of the coreboot project. |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; version 2 of the License. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| */ |
| |
| #include <types.h> |
| #include <symbols.h> |
| #include <device/mmio.h> |
| #include <ramdetect.h> |
| #include <console/console.h> |
| |
| #define OVERLAP(a, b, s, e) ((b) > (s) && (a) < (e)) |
| |
| static int probe_mb(const uintptr_t dram_start, const uintptr_t size) |
| { |
| uintptr_t addr = dram_start + (size * MiB) - sizeof(uint32_t); |
| static const uint32_t patterns[] = { |
| 0x55aa55aa, |
| 0x12345678 |
| }; |
| void *ptr = (void *) addr; |
| size_t i; |
| |
| /* Don't accidentally clober oneself. */ |
| if (OVERLAP(addr, addr + sizeof(uint32_t), (uintptr_t)_program, (uintptr_t) _eprogram)) |
| return 1; |
| |
| uint32_t old = read32(ptr); |
| for (i = 0; i < ARRAY_SIZE(patterns); i++) { |
| write32(ptr, patterns[i]); |
| if (read32(ptr) != patterns[i]) |
| break; |
| } |
| |
| write32(ptr, old); |
| return i == ARRAY_SIZE(patterns); |
| } |
| |
| /* - 20 as probe_size is in MiB, - 1 as i is signed */ |
| #define MAX_ADDRESSABLE_SPACE (sizeof(size_t) * 8 - 20 - 1) |
| |
| /* Probe an area if it's read/writable. */ |
| size_t probe_ramsize(const uintptr_t dram_start, const size_t probe_size) |
| { |
| ssize_t i; |
| size_t msb = 0; |
| size_t discovered = 0; |
| |
| static size_t saved_result; |
| if (saved_result) |
| return saved_result; |
| |
| /* Find the MSB + 1. */ |
| size_t tmp = probe_size; |
| do { |
| msb++; |
| } while (tmp >>= 1); |
| |
| /* Limit search to accessible address space */ |
| msb = MIN(msb, MAX_ADDRESSABLE_SPACE); |
| |
| /* Compact binary search. */ |
| for (i = msb; i >= 0; i--) |
| if (probe_mb(dram_start, (discovered | (1ULL << i)))) |
| discovered |= (1ULL << i); |
| |
| saved_result = discovered; |
| printk(BIOS_DEBUG, "RAMDETECT: Found %zu MiB RAM\n", discovered); |
| return discovered; |
| } |