68 lines
1.6 KiB
C
68 lines
1.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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#include <types.h>
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#include <symbols.h>
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#include <device/mmio.h>
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#include <ramdetect.h>
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#include <console/console.h>
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#define OVERLAP(a, b, s, e) ((b) > (s) && (a) < (e))
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int __weak probe_mb(const uintptr_t dram_start, const uintptr_t size)
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{
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uintptr_t addr = dram_start + (size * MiB) - sizeof(uint32_t);
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static const uint32_t patterns[] = {
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0x55aa55aa,
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0x12345678
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};
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void *ptr = (void *) addr;
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size_t i;
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/* Don't accidentally clober oneself. */
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if (OVERLAP(addr, addr + sizeof(uint32_t), (uintptr_t)_program, (uintptr_t) _eprogram))
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return 1;
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uint32_t old = read32(ptr);
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for (i = 0; i < ARRAY_SIZE(patterns); i++) {
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write32(ptr, patterns[i]);
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if (read32(ptr) != patterns[i])
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break;
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}
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write32(ptr, old);
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return i == ARRAY_SIZE(patterns);
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}
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/* - 20 as probe_size is in MiB, - 1 as i is signed */
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#define MAX_ADDRESSABLE_SPACE (sizeof(size_t) * 8 - 20 - 1)
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/* Probe an area if it's read/writable. */
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size_t probe_ramsize(const uintptr_t dram_start, const size_t probe_size)
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{
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ssize_t i;
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size_t msb = 0;
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size_t discovered = 0;
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static size_t saved_result;
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if (saved_result)
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return saved_result;
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/* Find the MSB + 1. */
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size_t tmp = probe_size;
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do {
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msb++;
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} while (tmp >>= 1);
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/* Limit search to accessible address space */
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msb = MIN(msb, MAX_ADDRESSABLE_SPACE);
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/* Compact binary search. */
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for (i = msb; i >= 0; i--)
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if (probe_mb(dram_start, (discovered | (1ULL << i))))
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discovered |= (1ULL << i);
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saved_result = discovered;
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printk(BIOS_DEBUG, "RAMDETECT: Found %zu MiB RAM\n", discovered);
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return discovered;
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}
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