// SPDX-License-Identifier: GPL-2.0
/*
 * 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/memblock.h>
#include <linux/types.h>

#include <asm/addrspace.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 __init 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);

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

/*
 * Use the REX prom calls to get hold of the memory bitmap, and thence
 * determine memory size.
 */
static __init 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 {
                        memblock_add(mem_start, mem_size);
                        mem_start += mem_size + (8 * bm->pagesize);
                        mem_size = 0;
                }
        }
        if (mem_size)
                memblock_add(mem_start, mem_size);
}

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);
}