/* SPDX-License-Identifier: GPL-2.0-only */ #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)) int __weak 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 clobber 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 ((discovered | (1ULL << i)) > probe_size) continue; 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; }