memory.c

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/*
 * memory.c: memory initialisation code.
 *
 * Copyright (C) 1998 Harald Koerfgen, Frieder Streffer and Paul M. Antoine
 * Copyright (C) 2000, 2002  Maciej W. Rozycki
 */
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/bootmem.h>
#include <linux/types.h>

#include <asm/addrspace.h>
#include <asm/bootinfo.h>
#include <asm/dec/machtype.h>
#include <asm/dec/prom.h>
#include <asm/page.h>
#include <asm/sections.h>


volatile unsigned long mem_err;     /* So we know an error occurred */

/*
 * Probe memory in 4MB chunks, waiting for an error to tell us we've fallen
 * off the end of real memory.  Only suitable for the 2100/3100's (PMAX).
 */

#define CHUNK_SIZE 0x400000

static inline void pmax_setup_memory_region(void)
{
    volatile unsigned char *memory_page, dummy;
    char old_handler[0x80];
    extern char genexcept_early;

    /* Install exception handler */
    memcpy(&old_handler, (void *)(CKSEG0 + 0x80), 0x80);
    memcpy((void *)(CKSEG0 + 0x80), &genexcept_early, 0x80);

    /* read unmapped and uncached (KSEG1)
     * DECstations have at least 4MB RAM
     * Assume less than 480MB of RAM, as this is max for 5000/2xx
     * FIXME this should be replaced by the first free page!
     */
    for (memory_page = (unsigned char *)CKSEG1 + CHUNK_SIZE;
         mem_err == 0 && memory_page < (unsigned char *)CKSEG1 + 0x1e00000;
         memory_page += CHUNK_SIZE) {
        dummy = *memory_page;
    }
    memcpy((void *)(CKSEG0 + 0x80), &old_handler, 0x80);

    add_memory_region(0, (unsigned long)memory_page - CKSEG1 - CHUNK_SIZE,
              BOOT_MEM_RAM);
}

/*
 * Use the REX prom calls to get hold of the memory bitmap, and thence
 * determine memory size.
 */
static inline void rex_setup_memory_region(void)
{
    int i, bitmap_size;
    unsigned long mem_start = 0, mem_size = 0;
    memmap *bm;

    /* some free 64k */
    bm = (memmap *)CKSEG0ADDR(0x28000);

    bitmap_size = rex_getbitmap(bm);

    for (i = 0; i < bitmap_size; i++) {
        /* FIXME: very simplistically only add full sets of pages */
        if (bm->bitmap[i] == 0xff)
            mem_size += (8 * bm->pagesize);
        else if (!mem_size)
            mem_start += (8 * bm->pagesize);
        else {
            add_memory_region(mem_start, mem_size, BOOT_MEM_RAM);
            mem_start += mem_size + (8 * bm->pagesize);
            mem_size = 0;
        }
    }
    if (mem_size)
        add_memory_region(mem_start, mem_size, BOOT_MEM_RAM);
}

void __init prom_meminit(u32 magic)
{
    if (!prom_is_rex(magic))
        pmax_setup_memory_region();
    else
        rex_setup_memory_region();
}

void __init prom_free_prom_memory(void)
{
    unsigned long end;

    /*
     * Free everything below the kernel itself but leave
     * the first page reserved for the exception handlers.
     */

#if IS_ENABLED(CONFIG_DECLANCE)
    /*
     * Leave 128 KB reserved for Lance memory for
     * IOASIC DECstations.
     *
     * XXX: save this address for use in dec_lance.c?
     */
    if (IOASIC)
        end = __pa(&_text) - 0x00020000;
    else
#endif
        end = __pa(&_text);

    free_init_pages("unused PROM memory", PAGE_SIZE, end);
}