1// SPDX-License-Identifier: GPL-2.0
2/*
3 * memory.c: memory initialisation code.
4 *
5 * Copyright (C) 1998 Harald Koerfgen, Frieder Streffer and Paul M. Antoine
6 * Copyright (C) 2000, 2002 Maciej W. Rozycki
7 */
8#include <linux/init.h>
9#include <linux/kernel.h>
10#include <linux/mm.h>
11#include <linux/memblock.h>
12#include <linux/types.h>
13
14#include <asm/addrspace.h>
15#include <asm/dec/machtype.h>
16#include <asm/dec/prom.h>
17#include <asm/page.h>
18#include <asm/sections.h>
19
20
21volatile unsigned long mem_err; /* So we know an error occurred */
22
23/*
24 * Probe memory in 4MB chunks, waiting for an error to tell us we've fallen
25 * off the end of real memory. Only suitable for the 2100/3100's (PMAX).
26 */
27
28#define CHUNK_SIZE 0x400000
29
30static __init void pmax_setup_memory_region(void)
31{
32 volatile unsigned char *memory_page, dummy;
33 char old_handler[0x80];
34 extern char genexcept_early;
35
36 /* Install exception handler */
37 memcpy(&old_handler, (void *)(CKSEG0 + 0x80), 0x80);
38 memcpy((void *)(CKSEG0 + 0x80), &genexcept_early, 0x80);
39
40 /* read unmapped and uncached (KSEG1)
41 * DECstations have at least 4MB RAM
42 * Assume less than 480MB of RAM, as this is max for 5000/2xx
43 * FIXME this should be replaced by the first free page!
44 */
45 for (memory_page = (unsigned char *)CKSEG1 + CHUNK_SIZE;
46 mem_err == 0 && memory_page < (unsigned char *)CKSEG1 + 0x1e00000;
47 memory_page += CHUNK_SIZE) {
48 dummy = *memory_page;
49 }
50 memcpy((void *)(CKSEG0 + 0x80), &old_handler, 0x80);
51
52 memblock_add(base: 0, size: (unsigned long)memory_page - CKSEG1 - CHUNK_SIZE);
53}
54
55/*
56 * Use the REX prom calls to get hold of the memory bitmap, and thence
57 * determine memory size.
58 */
59static __init void rex_setup_memory_region(void)
60{
61 int i, bitmap_size;
62 unsigned long mem_start = 0, mem_size = 0;
63 memmap *bm;
64
65 /* some free 64k */
66 bm = (memmap *)CKSEG0ADDR(0x28000);
67
68 bitmap_size = rex_getbitmap(bm);
69
70 for (i = 0; i < bitmap_size; i++) {
71 /* FIXME: very simplistically only add full sets of pages */
72 if (bm->bitmap[i] == 0xff)
73 mem_size += (8 * bm->pagesize);
74 else if (!mem_size)
75 mem_start += (8 * bm->pagesize);
76 else {
77 memblock_add(base: mem_start, size: mem_size);
78 mem_start += mem_size + (8 * bm->pagesize);
79 mem_size = 0;
80 }
81 }
82 if (mem_size)
83 memblock_add(base: mem_start, size: mem_size);
84}
85
86void __init prom_meminit(u32 magic)
87{
88 if (!prom_is_rex(magic))
89 pmax_setup_memory_region();
90 else
91 rex_setup_memory_region();
92}
93
94void __init prom_free_prom_memory(void)
95{
96 unsigned long end;
97
98 /*
99 * Free everything below the kernel itself but leave
100 * the first page reserved for the exception handlers.
101 */
102
103#if IS_ENABLED(CONFIG_DECLANCE)
104 /*
105 * Leave 128 KB reserved for Lance memory for
106 * IOASIC DECstations.
107 *
108 * XXX: save this address for use in dec_lance.c?
109 */
110 if (IOASIC)
111 end = __pa(&_text) - 0x00020000;
112 else
113#endif
114 end = __pa(&_text);
115
116 free_init_pages(what: "unused PROM memory", PAGE_SIZE, end);
117}
118

source code of linux/arch/mips/dec/prom/memory.c