LXR linux/arch/mips/dec/prom/memory.c

   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/bootinfo.h>
  16#include <asm/dec/machtype.h>
  17#include <asm/dec/prom.h>
  18#include <asm/page.h>
  19#include <asm/sections.h>
  20
  21
  22volatile unsigned long mem_err;         /* So we know an error occurred */
  23
  24/*
  25 * Probe memory in 4MB chunks, waiting for an error to tell us we've fallen
  26 * off the end of real memory.  Only suitable for the 2100/3100's (PMAX).
  27 */
  28
  29#define CHUNK_SIZE 0x400000
  30
  31static inline void pmax_setup_memory_region(void)
  32{
  33        volatile unsigned char *memory_page, dummy;
  34        char old_handler[0x80];
  35        extern char genexcept_early;
  36
  37        /* Install exception handler */
  38        memcpy(&old_handler, (void *)(CKSEG0 + 0x80), 0x80);
  39        memcpy((void *)(CKSEG0 + 0x80), &genexcept_early, 0x80);
  40
  41        /* read unmapped and uncached (KSEG1)
  42         * DECstations have at least 4MB RAM
  43         * Assume less than 480MB of RAM, as this is max for 5000/2xx
  44         * FIXME this should be replaced by the first free page!
  45         */
  46        for (memory_page = (unsigned char *)CKSEG1 + CHUNK_SIZE;
  47             mem_err == 0 && memory_page < (unsigned char *)CKSEG1 + 0x1e00000;
  48             memory_page += CHUNK_SIZE) {
  49                dummy = *memory_page;
  50        }
  51        memcpy((void *)(CKSEG0 + 0x80), &old_handler, 0x80);
  52
  53        add_memory_region(0, (unsigned long)memory_page - CKSEG1 - CHUNK_SIZE,
  54                          BOOT_MEM_RAM);
  55}
  56
  57/*
  58 * Use the REX prom calls to get hold of the memory bitmap, and thence
  59 * determine memory size.
  60 */
  61static inline void rex_setup_memory_region(void)
  62{
  63        int i, bitmap_size;
  64        unsigned long mem_start = 0, mem_size = 0;
  65        memmap *bm;
  66
  67        /* some free 64k */
  68        bm = (memmap *)CKSEG0ADDR(0x28000);
  69
  70        bitmap_size = rex_getbitmap(bm);
  71
  72        for (i = 0; i < bitmap_size; i++) {
  73                /* FIXME: very simplistically only add full sets of pages */
  74                if (bm->bitmap[i] == 0xff)
  75                        mem_size += (8 * bm->pagesize);
  76                else if (!mem_size)
  77                        mem_start += (8 * bm->pagesize);
  78                else {
  79                        add_memory_region(mem_start, mem_size, BOOT_MEM_RAM);
  80                        mem_start += mem_size + (8 * bm->pagesize);
  81                        mem_size = 0;
  82                }
  83        }
  84        if (mem_size)
  85                add_memory_region(mem_start, mem_size, BOOT_MEM_RAM);
  86}
  87
  88void __init prom_meminit(u32 magic)
  89{
  90        if (!prom_is_rex(magic))
  91                pmax_setup_memory_region();
  92        else
  93                rex_setup_memory_region();
  94}
  95
  96void __init prom_free_prom_memory(void)
  97{
  98        unsigned long end;
  99
 100        /*
 101         * Free everything below the kernel itself but leave
 102         * the first page reserved for the exception handlers.
 103         */
 104
 105#if IS_ENABLED(CONFIG_DECLANCE)
 106        /*
 107         * Leave 128 KB reserved for Lance memory for
 108         * IOASIC DECstations.
 109         *
 110         * XXX: save this address for use in dec_lance.c?
 111         */
 112        if (IOASIC)
 113                end = __pa(&_text) - 0x00020000;
 114        else
 115#endif
 116                end = __pa(&_text);
 117
 118        free_init_pages("unused PROM memory", PAGE_SIZE, end);
 119}
 120