1 // SPDX-License-Identifier: GPL-2.0-or-later
4 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
6 * Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
7 * and Cort Dougan (PReP) (cort@cs.nmt.edu)
8 * Copyright (C) 1996 Paul Mackerras
9 * PPC44x/36-bit changes by Matt Porter (mporter@mvista.com)
11 * Derived from "arch/i386/mm/init.c"
12 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
15 #include <linux/module.h>
16 #include <linux/sched.h>
17 #include <linux/kernel.h>
18 #include <linux/errno.h>
19 #include <linux/string.h>
20 #include <linux/types.h>
22 #include <linux/stddef.h>
23 #include <linux/init.h>
24 #include <linux/highmem.h>
25 #include <linux/initrd.h>
26 #include <linux/pagemap.h>
27 #include <linux/memblock.h>
28 #include <linux/gfp.h>
29 #include <linux/slab.h>
30 #include <linux/hugetlb.h>
32 #include <asm/pgalloc.h>
37 #include <asm/machdep.h>
38 #include <asm/btext.h>
40 #include <asm/sections.h>
41 #include <asm/hugetlb.h>
43 #include <asm/kasan.h>
45 #include <mm/mmu_decl.h>
47 #if defined(CONFIG_KERNEL_START_BOOL) || defined(CONFIG_LOWMEM_SIZE_BOOL)
48 /* The amount of lowmem must be within 0xF0000000 - KERNELBASE. */
49 #if (CONFIG_LOWMEM_SIZE > (0xF0000000 - PAGE_OFFSET))
50 #error "You must adjust CONFIG_LOWMEM_SIZE or CONFIG_KERNEL_START"
53 #define MAX_LOW_MEM CONFIG_LOWMEM_SIZE
55 phys_addr_t total_memory;
56 phys_addr_t total_lowmem;
58 #ifdef CONFIG_RELOCATABLE
59 /* Used in __va()/__pa() */
60 long long virt_phys_offset;
61 EXPORT_SYMBOL(virt_phys_offset);
64 phys_addr_t lowmem_end_addr;
67 #ifdef CONFIG_PPC_PMAC
68 unsigned long agp_special_page;
69 EXPORT_SYMBOL(agp_special_page);
75 * this tells the system to map all of ram with the segregs
76 * (i.e. page tables) instead of the bats.
79 int __map_without_bats;
80 int __map_without_ltlbs;
82 /* max amount of low RAM to map in */
83 unsigned long __max_low_memory = MAX_LOW_MEM;
86 * Check for command-line options that affect what MMU_init will do.
88 static void __init MMU_setup(void)
90 /* Check for nobats option (used in mapin_ram). */
91 if (strstr(boot_command_line, "nobats")) {
92 __map_without_bats = 1;
95 if (strstr(boot_command_line, "noltlbs")) {
96 __map_without_ltlbs = 1;
98 if (IS_ENABLED(CONFIG_PPC_8xx))
101 if (debug_pagealloc_enabled())
102 __map_without_ltlbs = 1;
104 if (strict_kernel_rwx_enabled())
105 __map_without_ltlbs = 1;
109 * MMU_init sets up the basic memory mappings for the kernel,
110 * including both RAM and possibly some I/O regions,
111 * and sets up the page tables and the MMU hardware ready to go.
113 void __init MMU_init(void)
116 ppc_md.progress("MMU:enter", 0x111);
118 /* parse args from command line */
122 * Reserve gigantic pages for hugetlb. This MUST occur before
123 * lowmem_end_addr is initialized below.
125 if (memblock.memory.cnt > 1) {
127 memblock_enforce_memory_limit(memblock.memory.regions[0].size);
128 pr_warn("Only using first contiguous memory region\n");
134 total_lowmem = total_memory = memblock_end_of_DRAM() - memstart_addr;
135 lowmem_end_addr = memstart_addr + total_lowmem;
137 #ifdef CONFIG_FSL_BOOKE
138 /* Freescale Book-E parts expect lowmem to be mapped by fixed TLB
139 * entries, so we need to adjust lowmem to match the amount we can map
140 * in the fixed entries */
141 adjust_total_lowmem();
142 #endif /* CONFIG_FSL_BOOKE */
144 if (total_lowmem > __max_low_memory) {
145 total_lowmem = __max_low_memory;
146 lowmem_end_addr = memstart_addr + total_lowmem;
147 #ifndef CONFIG_HIGHMEM
148 total_memory = total_lowmem;
149 memblock_enforce_memory_limit(total_lowmem);
150 #endif /* CONFIG_HIGHMEM */
153 /* Initialize the MMU hardware */
155 ppc_md.progress("MMU:hw init", 0x300);
158 /* Map in all of RAM starting at KERNELBASE */
160 ppc_md.progress("MMU:mapin", 0x301);
163 /* Initialize early top-down ioremap allocator */
164 ioremap_bot = IOREMAP_TOP;
167 ppc_md.progress("MMU:exit", 0x211);
169 /* From now on, btext is no longer BAT mapped if it was at all */
170 #ifdef CONFIG_BOOTX_TEXT
176 /* Shortly after that, the entire linear mapping will be available */
177 memblock_set_current_limit(lowmem_end_addr);