arch/m68k/mm/motorola.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * linux/arch/m68k/mm/motorola.c
  *
  * Routines specific to the Motorola MMU, originally from:
  * linux/arch/m68k/init.c
  * which are Copyright (C) 1995 Hamish Macdonald
  *
  * Moved 8/20/1999 Sam Creasey
  */

 #include <linux/module.h>
 #include <linux/signal.h>
 #include <linux/sched.h>
 #include <linux/mm.h>
 #include <linux/swap.h>
 #include <linux/kernel.h>
 #include <linux/string.h>
 #include <linux/types.h>
 #include <linux/init.h>
 #include <linux/memblock.h>
 #include <linux/gfp.h>

 #include <asm/setup.h>
 #include <linux/uaccess.h>
 #include <asm/page.h>
 #include <asm/pgalloc.h>
 #include <asm/machdep.h>
 #include <asm/io.h>
 #include <asm/dma.h>
 #ifdef CONFIG_ATARI
 #include <asm/atari_stram.h>
 #endif
 #include <asm/sections.h>

 #undef DEBUG

 #ifndef mm_cachebits
 /*
  * Bits to add to page descriptors for "normal" caching mode.
  * For 68020/030 this is 0.
  * For 68040, this is _PAGE_CACHE040 (cachable, copyback)
  */
 unsigned long mm_cachebits;
 EXPORT_SYMBOL(mm_cachebits);
 #endif

 /* Prior to calling these routines, the page should have been flushed
  * from both the cache and ATC, or the CPU might not notice that the
  * cache setting for the page has been changed. -jskov
  */
 static inline void nocache_page(void *vaddr)
 {
 	unsigned long addr = (unsigned long)vaddr;

 	if (CPU_IS_040_OR_060) {
 		pte_t *ptep = virt_to_kpte(addr);

 		*ptep = pte_mknocache(*ptep);
 	}
 }

 static inline void cache_page(void *vaddr)
 {
 	unsigned long addr = (unsigned long)vaddr;

 	if (CPU_IS_040_OR_060) {
 		pte_t *ptep = virt_to_kpte(addr);

 		*ptep = pte_mkcache(*ptep);
 	}
 }

 /*
  * Motorola 680x0 user's manual recommends using uncached memory for address
  * translation tables.
  *
  * Seeing how the MMU can be external on (some of) these chips, that seems like
  * a very important recommendation to follow. Provide some helpers to combat
  * 'variation' amongst the users of this.
  */

 void mmu_page_ctor(void *page)
 {
 	__flush_page_to_ram(page);
 	flush_tlb_kernel_page(page);
 	nocache_page(page);
 }

 void mmu_page_dtor(void *page)
 {
 	cache_page(page);
 }

 /* ++andreas: {get,free}_pointer_table rewritten to use unused fields from
    struct page instead of separately kmalloced struct.  Stolen from
    arch/sparc/mm/srmmu.c ... */

 typedef struct list_head ptable_desc;

 static struct list_head ptable_list[2] = {
 	LIST_HEAD_INIT(ptable_list[0]),
 	LIST_HEAD_INIT(ptable_list[1]),
 };

 #define PD_PTABLE(page) ((ptable_desc *)&(virt_to_page(page)->lru))
 #define PD_PAGE(ptable) (list_entry(ptable, struct page, lru))
 #define PD_MARKBITS(dp) (*(unsigned int *)&PD_PAGE(dp)->index)

 static const int ptable_shift[2] = {
 	7+2, /* PGD, PMD */
 	6+2, /* PTE */
 };

 #define ptable_size(type) (1U << ptable_shift[type])
 #define ptable_mask(type) ((1U << (PAGE_SIZE / ptable_size(type))) - 1)

 void __init init_pointer_table(void *table, int type)
 {
 	ptable_desc *dp;
 	unsigned long ptable = (unsigned long)table;
 	unsigned long page = ptable & PAGE_MASK;
 	unsigned int mask = 1U << ((ptable - page)/ptable_size(type));

 	dp = PD_PTABLE(page);
 	if (!(PD_MARKBITS(dp) & mask)) {
 		PD_MARKBITS(dp) = ptable_mask(type);
 		list_add(dp, &ptable_list[type]);
 	}

 	PD_MARKBITS(dp) &= ~mask;
 	pr_debug("init_pointer_table: %lx, %x\n", ptable, PD_MARKBITS(dp));

 	/* unreserve the page so it's possible to free that page */
 	__ClearPageReserved(PD_PAGE(dp));
 	init_page_count(PD_PAGE(dp));

 	return;
 }

 void *get_pointer_table(int type)
 {
 	ptable_desc *dp = ptable_list[type].next;
 	unsigned int mask = list_empty(&ptable_list[type]) ? 0 : PD_MARKBITS(dp);
 	unsigned int tmp, off;

 	/*
 	 * For a pointer table for a user process address space, a
 	 * table is taken from a page allocated for the purpose.  Each
 	 * page can hold 8 pointer tables.  The page is remapped in
 	 * virtual address space to be noncacheable.
 	 */
 	if (mask == 0) {
 		void *page;
 		ptable_desc *new;

 		if (!(page = (void *)get_zeroed_page(GFP_KERNEL)))
 			return NULL;

 		if (type == TABLE_PTE) {
 			/*
 			 * m68k doesn't have SPLIT_PTE_PTLOCKS for not having
 			 * SMP.
 			 */
 			pgtable_pte_page_ctor(virt_to_page(page));
 		}

 		mmu_page_ctor(page);

 		new = PD_PTABLE(page);
 		PD_MARKBITS(new) = ptable_mask(type) - 1;
 		list_add_tail(new, dp);

 		return (pmd_t *)page;
 	}

 	for (tmp = 1, off = 0; (mask & tmp) == 0; tmp <<= 1, off += ptable_size(type))
 		;
 	PD_MARKBITS(dp) = mask & ~tmp;
 	if (!PD_MARKBITS(dp)) {
 		/* move to end of list */
 		list_move_tail(dp, &ptable_list[type]);
 	}
 	return page_address(PD_PAGE(dp)) + off;
 }

 int free_pointer_table(void *table, int type)
 {
 	ptable_desc *dp;
 	unsigned long ptable = (unsigned long)table;
 	unsigned long page = ptable & PAGE_MASK;
 	unsigned int mask = 1U << ((ptable - page)/ptable_size(type));

 	dp = PD_PTABLE(page);
 	if (PD_MARKBITS (dp) & mask)
 		panic ("table already free!");

 	PD_MARKBITS (dp) |= mask;

 	if (PD_MARKBITS(dp) == ptable_mask(type)) {
 		/* all tables in page are free, free page */
 		list_del(dp);
 		mmu_page_dtor((void *)page);
 		if (type == TABLE_PTE)
 			pgtable_pte_page_dtor(virt_to_page(page));
 		free_page (page);
 		return 1;
 	} else if (ptable_list[type].next != dp) {
 		/*
 		 * move this descriptor to the front of the list, since
 		 * it has one or more free tables.
 		 */
 		list_move(dp, &ptable_list[type]);
 	}
 	return 0;
 }

 /* size of memory already mapped in head.S */
 extern __initdata unsigned long m68k_init_mapped_size;

 extern unsigned long availmem;

 static pte_t *last_pte_table __initdata = NULL;

 static pte_t * __init kernel_page_table(void)
 {
 	pte_t *pte_table = last_pte_table;

 	if (PAGE_ALIGNED(last_pte_table)) {
 		pte_table = memblock_alloc_low(PAGE_SIZE, PAGE_SIZE);
 		if (!pte_table) {
 			panic("%s: Failed to allocate %lu bytes align=%lx\n",
 					__func__, PAGE_SIZE, PAGE_SIZE);
 		}

 		clear_page(pte_table);
 		mmu_page_ctor(pte_table);

 		last_pte_table = pte_table;
 	}

 	last_pte_table += PTRS_PER_PTE;

 	return pte_table;
 }

 static pmd_t *last_pmd_table __initdata = NULL;

 static pmd_t * __init kernel_ptr_table(void)
 {
 	if (!last_pmd_table) {
 		unsigned long pmd, last;
 		int i;

 		/* Find the last ptr table that was used in head.S and
 		 * reuse the remaining space in that page for further
 		 * ptr tables.
 		 */
 		last = (unsigned long)kernel_pg_dir;
 		for (i = 0; i < PTRS_PER_PGD; i++) {
 			pud_t *pud = (pud_t *)(&kernel_pg_dir[i]);

 			if (!pud_present(*pud))
 				continue;
 			pmd = pgd_page_vaddr(kernel_pg_dir[i]);
 			if (pmd > last)
 				last = pmd;
 		}

 		last_pmd_table = (pmd_t *)last;
 #ifdef DEBUG
 		printk("kernel_ptr_init: %p\n", last_pmd_table);
 #endif
 	}

 	last_pmd_table += PTRS_PER_PMD;
 	if (PAGE_ALIGNED(last_pmd_table)) {
 		last_pmd_table = memblock_alloc_low(PAGE_SIZE, PAGE_SIZE);
 		if (!last_pmd_table)
 			panic("%s: Failed to allocate %lu bytes align=%lx\n",
 			      __func__, PAGE_SIZE, PAGE_SIZE);

 		clear_page(last_pmd_table);
 		mmu_page_ctor(last_pmd_table);
 	}

 	return last_pmd_table;
 }

 static void __init map_node(int node)
 {
 	unsigned long physaddr, virtaddr, size;
 	pgd_t *pgd_dir;
 	p4d_t *p4d_dir;
 	pud_t *pud_dir;
 	pmd_t *pmd_dir;
 	pte_t *pte_dir;

 	size = m68k_memory[node].size;
 	physaddr = m68k_memory[node].addr;
 	virtaddr = (unsigned long)phys_to_virt(physaddr);
 	physaddr |= m68k_supervisor_cachemode |
 		    _PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_DIRTY;
 	if (CPU_IS_040_OR_060)
 		physaddr |= _PAGE_GLOBAL040;

 	while (size > 0) {
 #ifdef DEBUG
 		if (!(virtaddr & (PMD_SIZE-1)))
 			printk ("\npa=%#lx va=%#lx ", physaddr & PAGE_MASK,
 				virtaddr);
 #endif
 		pgd_dir = pgd_offset_k(virtaddr);
 		if (virtaddr && CPU_IS_020_OR_030) {
 			if (!(virtaddr & (PGDIR_SIZE-1)) &&
 			    size >= PGDIR_SIZE) {
 #ifdef DEBUG
 				printk ("[very early term]");
 #endif
 				pgd_val(*pgd_dir) = physaddr;
 				size -= PGDIR_SIZE;
 				virtaddr += PGDIR_SIZE;
 				physaddr += PGDIR_SIZE;
 				continue;
 			}
 		}
 		p4d_dir = p4d_offset(pgd_dir, virtaddr);
 		pud_dir = pud_offset(p4d_dir, virtaddr);
 		if (!pud_present(*pud_dir)) {
 			pmd_dir = kernel_ptr_table();
 #ifdef DEBUG
 			printk ("[new pointer %p]", pmd_dir);
 #endif
 			pud_set(pud_dir, pmd_dir);
 		} else
 			pmd_dir = pmd_offset(pud_dir, virtaddr);

 		if (CPU_IS_020_OR_030) {
 			if (virtaddr) {
 #ifdef DEBUG
 				printk ("[early term]");
 #endif
 				pmd_val(*pmd_dir) = physaddr;
 				physaddr += PMD_SIZE;
 			} else {
 				int i;
 #ifdef DEBUG
 				printk ("[zero map]");
 #endif
 				pte_dir = kernel_page_table();
 				pmd_set(pmd_dir, pte_dir);

 				pte_val(*pte_dir++) = 0;
 				physaddr += PAGE_SIZE;
 				for (i = 1; i < PTRS_PER_PTE; physaddr += PAGE_SIZE, i++)
 					pte_val(*pte_dir++) = physaddr;
 			}
 			size -= PMD_SIZE;
 			virtaddr += PMD_SIZE;
 		} else {
 			if (!pmd_present(*pmd_dir)) {
 #ifdef DEBUG
 				printk ("[new table]");
 #endif
 				pte_dir = kernel_page_table();
 				pmd_set(pmd_dir, pte_dir);
 			}
 			pte_dir = pte_offset_kernel(pmd_dir, virtaddr);

 			if (virtaddr) {
 				if (!pte_present(*pte_dir))
 					pte_val(*pte_dir) = physaddr;
 			} else
 				pte_val(*pte_dir) = 0;
 			size -= PAGE_SIZE;
 			virtaddr += PAGE_SIZE;
 			physaddr += PAGE_SIZE;
 		}

 	}
 #ifdef DEBUG
 	printk("\n");
 #endif
 }

 /*
  * paging_init() continues the virtual memory environment setup which
  * was begun by the code in arch/head.S.
  */
 void __init paging_init(void)
 {
 	unsigned long max_zone_pfn[MAX_NR_ZONES] = { 0, };
 	unsigned long min_addr, max_addr;
 	unsigned long addr;
 	int i;

 #ifdef DEBUG
 	printk ("start of paging_init (%p, %lx)\n", kernel_pg_dir, availmem);
 #endif

 	/* Fix the cache mode in the page descriptors for the 680[46]0.  */
 	if (CPU_IS_040_OR_060) {
 		int i;
 #ifndef mm_cachebits
 		mm_cachebits = _PAGE_CACHE040;
 #endif
 		for (i = 0; i < 16; i++)
 			pgprot_val(protection_map[i]) |= _PAGE_CACHE040;
 	}

 	min_addr = m68k_memory[0].addr;
 	max_addr = min_addr + m68k_memory[0].size;
 	memblock_add_node(m68k_memory[0].addr, m68k_memory[0].size, 0,
 			  MEMBLOCK_NONE);
 	for (i = 1; i < m68k_num_memory;) {
 		if (m68k_memory[i].addr < min_addr) {
 			printk("Ignoring memory chunk at 0x%lx:0x%lx before the first chunk\n",
 				m68k_memory[i].addr, m68k_memory[i].size);
 			printk("Fix your bootloader or use a memfile to make use of this area!\n");
 			m68k_num_memory--;
 			memmove(m68k_memory + i, m68k_memory + i + 1,
 				(m68k_num_memory - i) * sizeof(struct m68k_mem_info));
 			continue;
 		}
 		memblock_add_node(m68k_memory[i].addr, m68k_memory[i].size, i,
 				  MEMBLOCK_NONE);
 		addr = m68k_memory[i].addr + m68k_memory[i].size;
 		if (addr > max_addr)
 			max_addr = addr;
 		i++;
 	}
 	m68k_memoffset = min_addr - PAGE_OFFSET;
 	m68k_virt_to_node_shift = fls(max_addr - min_addr - 1) - 6;

 	module_fixup(NULL, __start_fixup, __stop_fixup);
 	flush_icache();

 	high_memory = phys_to_virt(max_addr);

 	min_low_pfn = availmem >> PAGE_SHIFT;
 	max_pfn = max_low_pfn = max_addr >> PAGE_SHIFT;

 	/* Reserve kernel text/data/bss and the memory allocated in head.S */
 	memblock_reserve(m68k_memory[0].addr, availmem - m68k_memory[0].addr);

 	/*
 	 * Map the physical memory available into the kernel virtual
 	 * address space. Make sure memblock will not try to allocate
 	 * pages beyond the memory we already mapped in head.S
 	 */
 	memblock_set_bottom_up(true);

 	for (i = 0; i < m68k_num_memory; i++) {
 		m68k_setup_node(i);
 		map_node(i);
 	}

 	flush_tlb_all();

 	early_memtest(min_addr, max_addr);

 	/*
 	 * initialize the bad page table and bad page to point
 	 * to a couple of allocated pages
 	 */
 	empty_zero_page = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
 	if (!empty_zero_page)
 		panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
 		      __func__, PAGE_SIZE, PAGE_SIZE);

 	/*
 	 * Set up SFC/DFC registers
 	 */
 	set_fc(USER_DATA);

 #ifdef DEBUG
 	printk ("before free_area_init\n");
 #endif
 	for (i = 0; i < m68k_num_memory; i++)
 		if (node_present_pages(i))
 			node_set_state(i, N_NORMAL_MEMORY);

 	max_zone_pfn[ZONE_DMA] = memblock_end_of_DRAM();
 	free_area_init(max_zone_pfn);
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* linux/arch/m68k/mm/motorola.c
	*
	* Routines specific to the Motorola MMU, originally from:
	* linux/arch/m68k/init.c
	* which are Copyright (C) 1995 Hamish Macdonald
	*
	* Moved 8/20/1999 Sam Creasey
	*/

	#include <linux/module.h>
	#include <linux/signal.h>
	#include <linux/sched.h>
	#include <linux/mm.h>
	#include <linux/swap.h>
	#include <linux/kernel.h>
	#include <linux/string.h>
	#include <linux/types.h>
	#include <linux/init.h>
	#include <linux/memblock.h>
	#include <linux/gfp.h>

	#include <asm/setup.h>
	#include <linux/uaccess.h>
	#include <asm/page.h>
	#include <asm/pgalloc.h>
	#include <asm/machdep.h>
	#include <asm/io.h>
	#include <asm/dma.h>
	#ifdef CONFIG_ATARI
	#include <asm/atari_stram.h>
	#endif
	#include <asm/sections.h>

	#undef DEBUG

	#ifndef mm_cachebits
	/*
	* Bits to add to page descriptors for "normal" caching mode.
	* For 68020/030 this is 0.
	* For 68040, this is _PAGE_CACHE040 (cachable, copyback)
	*/
	unsigned long mm_cachebits;
	EXPORT_SYMBOL(mm_cachebits);
	#endif

	/* Prior to calling these routines, the page should have been flushed
	* from both the cache and ATC, or the CPU might not notice that the
	* cache setting for the page has been changed. -jskov
	*/
	static inline void nocache_page(void *vaddr)
	{
	unsigned long addr = (unsigned long)vaddr;

	if (CPU_IS_040_OR_060) {
	pte_t *ptep = virt_to_kpte(addr);

	ptep = pte_mknocache(ptep);
	}
	}

	static inline void cache_page(void *vaddr)
	{
	unsigned long addr = (unsigned long)vaddr;

	if (CPU_IS_040_OR_060) {
	pte_t *ptep = virt_to_kpte(addr);

	ptep = pte_mkcache(ptep);
	}
	}

	/*
	* Motorola 680x0 user's manual recommends using uncached memory for address
	* translation tables.
	*
	* Seeing how the MMU can be external on (some of) these chips, that seems like
	* a very important recommendation to follow. Provide some helpers to combat
	* 'variation' amongst the users of this.
	*/

	void mmu_page_ctor(void *page)
	{
	__flush_page_to_ram(page);
	flush_tlb_kernel_page(page);
	nocache_page(page);
	}

	void mmu_page_dtor(void *page)
	{
	cache_page(page);
	}

	/* ++andreas: {get,free}_pointer_table rewritten to use unused fields from
	struct page instead of separately kmalloced struct. Stolen from
	arch/sparc/mm/srmmu.c ... */

	typedef struct list_head ptable_desc;

	static struct list_head ptable_list[2] = {
	LIST_HEAD_INIT(ptable_list[0]),
	LIST_HEAD_INIT(ptable_list[1]),
	};

	#define PD_PTABLE(page) ((ptable_desc *)&(virt_to_page(page)->lru))
	#define PD_PAGE(ptable) (list_entry(ptable, struct page, lru))
	#define PD_MARKBITS(dp) ((unsigned int )&PD_PAGE(dp)->index)

	static const int ptable_shift[2] = {
	7+2, /* PGD, PMD */
	6+2, /* PTE */
	};

	#define ptable_size(type) (1U << ptable_shift[type])
	#define ptable_mask(type) ((1U << (PAGE_SIZE / ptable_size(type))) - 1)

	void __init init_pointer_table(void *table, int type)
	{
	ptable_desc *dp;
	unsigned long ptable = (unsigned long)table;
	unsigned long page = ptable & PAGE_MASK;
	unsigned int mask = 1U << ((ptable - page)/ptable_size(type));

	dp = PD_PTABLE(page);
	if (!(PD_MARKBITS(dp) & mask)) {
	PD_MARKBITS(dp) = ptable_mask(type);
	list_add(dp, &ptable_list[type]);
	}

	PD_MARKBITS(dp) &= ~mask;
	pr_debug("init_pointer_table: %lx, %x\n", ptable, PD_MARKBITS(dp));

	/* unreserve the page so it's possible to free that page */
	__ClearPageReserved(PD_PAGE(dp));
	init_page_count(PD_PAGE(dp));

	return;
	}

	void *get_pointer_table(int type)
	{
	ptable_desc *dp = ptable_list[type].next;
	unsigned int mask = list_empty(&ptable_list[type]) ? 0 : PD_MARKBITS(dp);
	unsigned int tmp, off;

	/*
	* For a pointer table for a user process address space, a
	* table is taken from a page allocated for the purpose. Each
	* page can hold 8 pointer tables. The page is remapped in
	* virtual address space to be noncacheable.
	*/
	if (mask == 0) {
	void *page;
	ptable_desc *new;

	if (!(page = (void *)get_zeroed_page(GFP_KERNEL)))
	return NULL;

	if (type == TABLE_PTE) {
	/*
	* m68k doesn't have SPLIT_PTE_PTLOCKS for not having
	* SMP.
	*/
	pgtable_pte_page_ctor(virt_to_page(page));
	}

	mmu_page_ctor(page);

	new = PD_PTABLE(page);
	PD_MARKBITS(new) = ptable_mask(type) - 1;
	list_add_tail(new, dp);

	return (pmd_t *)page;
	}

	for (tmp = 1, off = 0; (mask & tmp) == 0; tmp <<= 1, off += ptable_size(type))
	;
	PD_MARKBITS(dp) = mask & ~tmp;
	if (!PD_MARKBITS(dp)) {
	/* move to end of list */
	list_move_tail(dp, &ptable_list[type]);
	}
	return page_address(PD_PAGE(dp)) + off;
	}

	int free_pointer_table(void *table, int type)
	{
	ptable_desc *dp;
	unsigned long ptable = (unsigned long)table;
	unsigned long page = ptable & PAGE_MASK;
	unsigned int mask = 1U << ((ptable - page)/ptable_size(type));

	dp = PD_PTABLE(page);
	if (PD_MARKBITS (dp) & mask)
	panic ("table already free!");

	PD_MARKBITS (dp) \|= mask;

	if (PD_MARKBITS(dp) == ptable_mask(type)) {
	/* all tables in page are free, free page */
	list_del(dp);
	mmu_page_dtor((void *)page);
	if (type == TABLE_PTE)
	pgtable_pte_page_dtor(virt_to_page(page));
	free_page (page);
	return 1;
	} else if (ptable_list[type].next != dp) {
	/*
	* move this descriptor to the front of the list, since
	* it has one or more free tables.
	*/
	list_move(dp, &ptable_list[type]);
	}
	return 0;
	}

	/* size of memory already mapped in head.S */
	extern __initdata unsigned long m68k_init_mapped_size;

	extern unsigned long availmem;

	static pte_t *last_pte_table __initdata = NULL;

	static pte_t * __init kernel_page_table(void)
	{
	pte_t *pte_table = last_pte_table;

	if (PAGE_ALIGNED(last_pte_table)) {
	pte_table = memblock_alloc_low(PAGE_SIZE, PAGE_SIZE);
	if (!pte_table) {
	panic("%s: Failed to allocate %lu bytes align=%lx\n",
	__func__, PAGE_SIZE, PAGE_SIZE);
	}

	clear_page(pte_table);
	mmu_page_ctor(pte_table);

	last_pte_table = pte_table;
	}

	last_pte_table += PTRS_PER_PTE;

	return pte_table;
	}

	static pmd_t *last_pmd_table __initdata = NULL;

	static pmd_t * __init kernel_ptr_table(void)
	{
	if (!last_pmd_table) {
	unsigned long pmd, last;
	int i;

	/* Find the last ptr table that was used in head.S and
	* reuse the remaining space in that page for further
	* ptr tables.
	*/
	last = (unsigned long)kernel_pg_dir;
	for (i = 0; i < PTRS_PER_PGD; i++) {
	pud_t pud = (pud_t )(&kernel_pg_dir[i]);

	if (!pud_present(*pud))
	continue;
	pmd = pgd_page_vaddr(kernel_pg_dir[i]);
	if (pmd > last)
	last = pmd;
	}

	last_pmd_table = (pmd_t *)last;
	#ifdef DEBUG
	printk("kernel_ptr_init: %p\n", last_pmd_table);
	#endif
	}

	last_pmd_table += PTRS_PER_PMD;
	if (PAGE_ALIGNED(last_pmd_table)) {
	last_pmd_table = memblock_alloc_low(PAGE_SIZE, PAGE_SIZE);
	if (!last_pmd_table)
	panic("%s: Failed to allocate %lu bytes align=%lx\n",
	__func__, PAGE_SIZE, PAGE_SIZE);

	clear_page(last_pmd_table);
	mmu_page_ctor(last_pmd_table);
	}

	return last_pmd_table;
	}

	static void __init map_node(int node)
	{
	unsigned long physaddr, virtaddr, size;
	pgd_t *pgd_dir;
	p4d_t *p4d_dir;
	pud_t *pud_dir;
	pmd_t *pmd_dir;
	pte_t *pte_dir;

	size = m68k_memory[node].size;
	physaddr = m68k_memory[node].addr;
	virtaddr = (unsigned long)phys_to_virt(physaddr);
	physaddr \|= m68k_supervisor_cachemode \|
	_PAGE_PRESENT \| _PAGE_ACCESSED \| _PAGE_DIRTY;
	if (CPU_IS_040_OR_060)
	physaddr \|= _PAGE_GLOBAL040;

	while (size > 0) {
	#ifdef DEBUG
	if (!(virtaddr & (PMD_SIZE-1)))
	printk ("\npa=%#lx va=%#lx ", physaddr & PAGE_MASK,
	virtaddr);
	#endif
	pgd_dir = pgd_offset_k(virtaddr);
	if (virtaddr && CPU_IS_020_OR_030) {
	if (!(virtaddr & (PGDIR_SIZE-1)) &&
	size >= PGDIR_SIZE) {
	#ifdef DEBUG
	printk ("[very early term]");
	#endif
	pgd_val(*pgd_dir) = physaddr;
	size -= PGDIR_SIZE;
	virtaddr += PGDIR_SIZE;
	physaddr += PGDIR_SIZE;
	continue;
	}
	}
	p4d_dir = p4d_offset(pgd_dir, virtaddr);
	pud_dir = pud_offset(p4d_dir, virtaddr);
	if (!pud_present(*pud_dir)) {
	pmd_dir = kernel_ptr_table();
	#ifdef DEBUG
	printk ("[new pointer %p]", pmd_dir);
	#endif
	pud_set(pud_dir, pmd_dir);
	} else
	pmd_dir = pmd_offset(pud_dir, virtaddr);

	if (CPU_IS_020_OR_030) {
	if (virtaddr) {
	#ifdef DEBUG
	printk ("[early term]");
	#endif
	pmd_val(*pmd_dir) = physaddr;
	physaddr += PMD_SIZE;
	} else {
	int i;
	#ifdef DEBUG
	printk ("[zero map]");
	#endif
	pte_dir = kernel_page_table();
	pmd_set(pmd_dir, pte_dir);

	pte_val(*pte_dir++) = 0;
	physaddr += PAGE_SIZE;
	for (i = 1; i < PTRS_PER_PTE; physaddr += PAGE_SIZE, i++)
	pte_val(*pte_dir++) = physaddr;
	}
	size -= PMD_SIZE;
	virtaddr += PMD_SIZE;
	} else {
	if (!pmd_present(*pmd_dir)) {
	#ifdef DEBUG
	printk ("[new table]");
	#endif
	pte_dir = kernel_page_table();
	pmd_set(pmd_dir, pte_dir);
	}
	pte_dir = pte_offset_kernel(pmd_dir, virtaddr);

	if (virtaddr) {
	if (!pte_present(*pte_dir))
	pte_val(*pte_dir) = physaddr;
	} else
	pte_val(*pte_dir) = 0;
	size -= PAGE_SIZE;
	virtaddr += PAGE_SIZE;
	physaddr += PAGE_SIZE;
	}

	}
	#ifdef DEBUG
	printk("\n");
	#endif
	}

	/*
	* paging_init() continues the virtual memory environment setup which
	* was begun by the code in arch/head.S.
	*/
	void __init paging_init(void)
	{
	unsigned long max_zone_pfn[MAX_NR_ZONES] = { 0, };
	unsigned long min_addr, max_addr;
	unsigned long addr;
	int i;

	#ifdef DEBUG
	printk ("start of paging_init (%p, %lx)\n", kernel_pg_dir, availmem);
	#endif

	/* Fix the cache mode in the page descriptors for the 680[46]0. */
	if (CPU_IS_040_OR_060) {
	int i;
	#ifndef mm_cachebits
	mm_cachebits = _PAGE_CACHE040;
	#endif
	for (i = 0; i < 16; i++)
	pgprot_val(protection_map[i]) \|= _PAGE_CACHE040;
	}

	min_addr = m68k_memory[0].addr;
	max_addr = min_addr + m68k_memory[0].size;
	memblock_add_node(m68k_memory[0].addr, m68k_memory[0].size, 0,
	MEMBLOCK_NONE);
	for (i = 1; i < m68k_num_memory;) {
	if (m68k_memory[i].addr < min_addr) {
	printk("Ignoring memory chunk at 0x%lx:0x%lx before the first chunk\n",
	m68k_memory[i].addr, m68k_memory[i].size);
	printk("Fix your bootloader or use a memfile to make use of this area!\n");
	m68k_num_memory--;
	memmove(m68k_memory + i, m68k_memory + i + 1,
	(m68k_num_memory - i) * sizeof(struct m68k_mem_info));
	continue;
	}
	memblock_add_node(m68k_memory[i].addr, m68k_memory[i].size, i,
	MEMBLOCK_NONE);
	addr = m68k_memory[i].addr + m68k_memory[i].size;
	if (addr > max_addr)
	max_addr = addr;
	i++;
	}
	m68k_memoffset = min_addr - PAGE_OFFSET;
	m68k_virt_to_node_shift = fls(max_addr - min_addr - 1) - 6;

	module_fixup(NULL, __start_fixup, __stop_fixup);
	flush_icache();

	high_memory = phys_to_virt(max_addr);

	min_low_pfn = availmem >> PAGE_SHIFT;
	max_pfn = max_low_pfn = max_addr >> PAGE_SHIFT;

	/* Reserve kernel text/data/bss and the memory allocated in head.S */
	memblock_reserve(m68k_memory[0].addr, availmem - m68k_memory[0].addr);

	/*
	* Map the physical memory available into the kernel virtual
	* address space. Make sure memblock will not try to allocate
	* pages beyond the memory we already mapped in head.S
	*/
	memblock_set_bottom_up(true);

	for (i = 0; i < m68k_num_memory; i++) {
	m68k_setup_node(i);
	map_node(i);
	}

	flush_tlb_all();

	early_memtest(min_addr, max_addr);

	/*
	* initialize the bad page table and bad page to point
	* to a couple of allocated pages
	*/
	empty_zero_page = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
	if (!empty_zero_page)
	panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
	__func__, PAGE_SIZE, PAGE_SIZE);

	/*
	* Set up SFC/DFC registers
	*/
	set_fc(USER_DATA);

	#ifdef DEBUG
	printk ("before free_area_init\n");
	#endif
	for (i = 0; i < m68k_num_memory; i++)
	if (node_present_pages(i))
	node_set_state(i, N_NORMAL_MEMORY);

	max_zone_pfn[ZONE_DMA] = memblock_end_of_DRAM();
	free_area_init(max_zone_pfn);
	}