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
  22 volatile 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
  31 static 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  */
  61 static 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
  88 void __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
  96 void __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 }