xref: /openbmc/linux/arch/mips/dec/prom/memory.c (revision 3e4614e7)
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 
21 volatile 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 
pmax_setup_memory_region(void)30 static __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(0, (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  */
rex_setup_memory_region(void)59 static __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(mem_start, mem_size);
78 			mem_start += mem_size + (8 * bm->pagesize);
79 			mem_size = 0;
80 		}
81 	}
82 	if (mem_size)
83 		memblock_add(mem_start, mem_size);
84 }
85 
prom_meminit(u32 magic)86 void __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 
prom_free_prom_memory(void)94 void __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("unused PROM memory", PAGE_SIZE, end);
117 }
118