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/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
  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  */
  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
  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
  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 }