text: /*
   *  linux/arch/parisc/mm/init.c
   *
   *  Copyright (C) 1995	Linus Torvalds
   *  Copyright 1999 SuSE GmbH
   *    changed by Philipp Rumpf
   *  Copyright 1999 Philipp Rumpf (prumpf@tux.org)
   *  Copyright 2004 Randolph Chung (tausq@debian.org)
   *  Copyright 2006-2007 Helge Deller (deller@gmx.de)
   *
   */
  
  
  #include <linux/module.h>
  #include <linux/mm.h>
  #include <linux/bootmem.h>
  #include <linux/memblock.h>
  #include <linux/gfp.h>
  #include <linux/delay.h>
  #include <linux/init.h>
  #include <linux/pci.h>		/* for hppa_dma_ops and pcxl_dma_ops */
  #include <linux/initrd.h>
  #include <linux/swap.h>
  #include <linux/unistd.h>
  #include <linux/nodemask.h>	/* for node_online_map */
  #include <linux/pagemap.h>	/* for release_pages */
  #include <linux/compat.h>
  
  #include <asm/pgalloc.h>
  #include <asm/pgtable.h>
  #include <asm/tlb.h>
  #include <asm/pdc_chassis.h>
  #include <asm/mmzone.h>
  #include <asm/sections.h>
  #include <asm/msgbuf.h>
  
  extern int  data_start;
  extern void parisc_kernel_start(void);	/* Kernel entry point in head.S */
  
  #if CONFIG_PGTABLE_LEVELS == 3
  /* NOTE: This layout exactly conforms to the hybrid L2/L3 page table layout
   * with the first pmd adjacent to the pgd and below it. gcc doesn't actually
   * guarantee that global objects will be laid out in memory in the same order
   * as the order of declaration, so put these in different sections and use
   * the linker script to order them. */
  pmd_t pmd0[PTRS_PER_PMD] __attribute__ ((__section__ (".data..vm0.pmd"), aligned(PAGE_SIZE)));
  #endif
  
  pgd_t swapper_pg_dir[PTRS_PER_PGD] __attribute__ ((__section__ (".data..vm0.pgd"), aligned(PAGE_SIZE)));
  pte_t pg0[PT_INITIAL * PTRS_PER_PTE] __attribute__ ((__section__ (".data..vm0.pte"), aligned(PAGE_SIZE)));
  
  #ifdef CONFIG_DISCONTIGMEM
  struct node_map_data node_data[MAX_NUMNODES] __read_mostly;
  signed char pfnnid_map[PFNNID_MAP_MAX] __read_mostly;
  #endif
  
  static struct resource data_resource = {
  	.name	= "Kernel data",
  	.flags	= IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM,
  };
  
  static struct resource code_resource = {
  	.name	= "Kernel code",
  	.flags	= IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM,
  };
  
  static struct resource pdcdata_resource = {
  	.name	= "PDC data (Page Zero)",
  	.start	= 0,
  	.end	= 0x9ff,
  	.flags	= IORESOURCE_BUSY | IORESOURCE_MEM,
  };
  
  static struct resource sysram_resources[MAX_PHYSMEM_RANGES] __read_mostly;
  
  /* The following array is initialized from the firmware specific
   * information retrieved in kernel/inventory.c.
   */
  
  physmem_range_t pmem_ranges[MAX_PHYSMEM_RANGES] __read_mostly;
  int npmem_ranges __read_mostly;
  
  /*
   * get_memblock() allocates pages via memblock.
   * We can't use memblock_find_in_range(0, KERNEL_INITIAL_SIZE) here since it
   * doesn't allocate from bottom to top which is needed because we only created
   * the initial mapping up to KERNEL_INITIAL_SIZE in the assembly bootup code.
   */
  static void * __init get_memblock(unsigned long size)
  {
  	static phys_addr_t search_addr __initdata;
  	phys_addr_t phys;
  
  	if (!search_addr)
  		search_addr = PAGE_ALIGN(__pa((unsigned long) &_end));
  	search_addr = ALIGN(search_addr, size);
  	while (!memblock_is_region_memory(search_addr, size) ||
  		memblock_is_region_reserved(search_addr, size)) {
  		search_addr += size;
  	}
  	phys = search_addr;
  
  	if (phys)
  		memblock_reserve(phys, size);
  	else
  		panic("get_memblock() failed.\n");
  
  	memset(__va(phys), 0, size);
  
  	return __va(phys);
  }
  
  #ifdef CONFIG_64BIT
  #define MAX_MEM         (~0UL)
  #else /* !CONFIG_64BIT */
  #define MAX_MEM         (3584U*1024U*1024U)
  #endif /* !CONFIG_64BIT */
  
  static unsigned long mem_limit __read_mostly = MAX_MEM;
  
  static void __init mem_limit_func(void)
  {
  	char *cp, *end;
  	unsigned long limit;
  
  	/* We need this before __setup() functions are called */
  
  	limit = MAX_MEM;
  	for (cp = boot_command_line; *cp; ) {
  		if (memcmp(cp, "mem=", 4) == 0) {
  			cp += 4;
  			limit = memparse(cp, &end);
  			if (end != cp)
  				break;
  			cp = end;
  		} else {
  			while (*cp != ' ' && *cp)
  				++cp;
  			while (*cp == ' ')
  				++cp;
  		}
  	}
  
  	if (limit < mem_limit)
  		mem_limit = limit;
  }
  
  #define MAX_GAP (0x40000000UL >> PAGE_SHIFT)
  
  static void __init setup_bootmem(void)
  {
  	unsigned long mem_max;
  #ifndef CONFIG_DISCONTIGMEM
  	physmem_range_t pmem_holes[MAX_PHYSMEM_RANGES - 1];
  	int npmem_holes;
  #endif
  	int i, sysram_resource_count;
  
  	disable_sr_hashing(); /* Turn off space register hashing */
  
  	/*
  	 * Sort the ranges. Since the number of ranges is typically
  	 * small, and performance is not an issue here, just do
  	 * a simple insertion sort.
  	 */
  
  	for (i = 1; i < npmem_ranges; i++) {
  		int j;
  
  		for (j = i; j > 0; j--) {
  			unsigned long tmp;
  
  			if (pmem_ranges[j-1].start_pfn <
  			    pmem_ranges[j].start_pfn) {
  
  				break;
  			}
  			tmp = pmem_ranges[j-1].start_pfn;
  			pmem_ranges[j-1].start_pfn = pmem_ranges[j].start_pfn;
  			pmem_ranges[j].start_pfn = tmp;
  			tmp = pmem_ranges[j-1].pages;
  			pmem_ranges[j-1].pages = pmem_ranges[j].pages;
  			pmem_ranges[j].pages = tmp;
  		}
  	}
  
  #ifndef CONFIG_DISCONTIGMEM
  	/*
  	 * Throw out ranges that are too far apart (controlled by
  	 * MAX_GAP).
  	 */
  
  	for (i = 1; i < npmem_ranges; i++) {
  		if (pmem_ranges[i].start_pfn -
  			(pmem_ranges[i-1].start_pfn +
  			 pmem_ranges[i-1].pages) > MAX_GAP) {
  			npmem_ranges = i;
  			printk("Large gap in memory detected (%ld pages). "
  			       "Consider turning on CONFIG_DISCONTIGMEM\n",
  			       pmem_ranges[i].start_pfn -
  			       (pmem_ranges[i-1].start_pfn +
  			        pmem_ranges[i-1].pages));
  			break;
  		}
  	}
  #endif
  
  	/* Print the memory ranges */
  	pr_info("Memory Ranges:\n");
  
  	for (i = 0; i < npmem_ranges; i++) {
  		struct resource *res = &sysram_resources[i];
  		unsigned long start;
  		unsigned long size;
  
  		size = (pmem_ranges[i].pages << PAGE_SHIFT);
  		start = (pmem_ranges[i].start_pfn << PAGE_SHIFT);
  		pr_info("%2d) Start 0x%016lx End 0x%016lx Size %6ld MB\n",
  			i, start, start + (size - 1), size >> 20);
  
  		/* request memory resource */
  		res->name = "System RAM";
  		res->start = start;
  		res->end = start + size - 1;
  		res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
  		request_resource(&iomem_resource, res);
  	}
  
  	sysram_resource_count = npmem_ranges;
  
  	/*
  	 * For 32 bit kernels we limit the amount of memory we can
  	 * support, in order to preserve enough kernel address space
  	 * for other purposes. For 64 bit kernels we don't normally
  	 * limit the memory, but this mechanism can be used to
  	 * artificially limit the amount of memory (and it is written
  	 * to work with multiple memory ranges).
  	 */
  
  	mem_limit_func();       /* check for "mem=" argument */
  
  	mem_max = 0;
  	for (i = 0; i < npmem_ranges; i++) {
  		unsigned long rsize;
  
  		rsize = pmem_ranges[i].pages << PAGE_SHIFT;
  		if ((mem_max + rsize) > mem_limit) {
  			printk(KERN_WARNING "Memory truncated to %ld MB\n", mem_limit >> 20);
  			if (mem_max == mem_limit)
  				npmem_ranges = i;
  			else {
  				pmem_ranges[i].pages =   (mem_limit >> PAGE_SHIFT)
  						       - (mem_max >> PAGE_SHIFT);
  				npmem_ranges = i + 1;
  				mem_max = mem_limit;
  			}
  			break;
  		}
  		mem_max += rsize;
  	}
  
  	printk(KERN_INFO "Total Memory: %ld MB\n",mem_max >> 20);
  
  #ifndef CONFIG_DISCONTIGMEM
  	/* Merge the ranges, keeping track of the holes */
  
  	{
  		unsigned long end_pfn;
  		unsigned long hole_pages;
  
  		npmem_holes = 0;
  		end_pfn = pmem_ranges[0].start_pfn + pmem_ranges[0].pages;
  		for (i = 1; i < npmem_ranges; i++) {
  
  			hole_pages = pmem_ranges[i].start_pfn - end_pfn;
  			if (hole_pages) {
  				pmem_holes[npmem_holes].start_pfn = end_pfn;
  				pmem_holes[npmem_holes++].pages = hole_pages;
  				end_pfn += hole_pages;
  			}
  			end_pfn += pmem_ranges[i].pages;
  		}
  
  		pmem_ranges[0].pages = end_pfn - pmem_ranges[0].start_pfn;
  		npmem_ranges = 1;
  	}
  #endif
  
  #ifdef CONFIG_DISCONTIGMEM
  	for (i = 0; i < MAX_PHYSMEM_RANGES; i++) {
  		memset(NODE_DATA(i), 0, sizeof(pg_data_t));
  	}
  	memset(pfnnid_map, 0xff, sizeof(pfnnid_map));
  
  	for (i = 0; i < npmem_ranges; i++) {
  		node_set_state(i, N_NORMAL_MEMORY);
  		node_set_online(i);
  	}
  #endif
  
  	/*
  	 * Initialize and free the full range of memory in each range.
  	 */
  
  	max_pfn = 0;
  	for (i = 0; i < npmem_ranges; i++) {
  		unsigned long start_pfn;
  		unsigned long npages;
  		unsigned long start;
  		unsigned long size;
  
  		start_pfn = pmem_ranges[i].start_pfn;
  		npages = pmem_ranges[i].pages;
  
  		start = start_pfn << PAGE_SHIFT;
  		size = npages << PAGE_SHIFT;
  
  		/* add system RAM memblock */
  		memblock_add(start, size);
  
  		if ((start_pfn + npages) > max_pfn)
  			max_pfn = start_pfn + npages;
  	}
  
  	/* IOMMU is always used to access "high mem" on those boxes
  	 * that can support enough mem that a PCI device couldn't
  	 * directly DMA to any physical addresses.
  	 * ISA DMA support will need to revisit this.
  	 */
  	max_low_pfn = max_pfn;
  
  	/* reserve PAGE0 pdc memory, kernel text/data/bss & bootmap */
  
  #define PDC_CONSOLE_IO_IODC_SIZE 32768
  
  	memblock_reserve(0UL, (unsigned long)(PAGE0->mem_free +
  				PDC_CONSOLE_IO_IODC_SIZE));
  	memblock_reserve(__pa(KERNEL_BINARY_TEXT_START),
  			(unsigned long)(_end - KERNEL_BINARY_TEXT_START));
  
  #ifndef CONFIG_DISCONTIGMEM
  
  	/* reserve the holes */
  
  	for (i = 0; i < npmem_holes; i++) {
  		memblock_reserve((pmem_holes[i].start_pfn << PAGE_SHIFT),
  				(pmem_holes[i].pages << PAGE_SHIFT));
  	}
  #endif
  
  #ifdef CONFIG_BLK_DEV_INITRD
  	if (initrd_start) {
  		printk(KERN_INFO "initrd: %08lx-%08lx\n", initrd_start, initrd_end);
  		if (__pa(initrd_start) < mem_max) {
  			unsigned long initrd_reserve;
  
  			if (__pa(initrd_end) > mem_max) {
  				initrd_reserve = mem_max - __pa(initrd_start);
  			} else {
  				initrd_reserve = initrd_end - initrd_start;
  			}
  			initrd_below_start_ok = 1;
  			printk(KERN_INFO "initrd: reserving %08lx-%08lx (mem_max %08lx)\n", __pa(initrd_start), __pa(initrd_start) + initrd_reserve, mem_max);
  
  			memblock_reserve(__pa(initrd_start), initrd_reserve);
  		}
  	}
  #endif
  
  	data_resource.start =  virt_to_phys(&data_start);
  	data_resource.end = virt_to_phys(_end) - 1;
  	code_resource.start = virt_to_phys(_text);
  	code_resource.end = virt_to_phys(&data_start)-1;
  
  	/* We don't know which region the kernel will be in, so try
  	 * all of them.
  	 */
  	for (i = 0; i < sysram_resource_count; i++) {
  		struct resource *res = &sysram_resources[i];
  		request_resource(res, &code_resource);
  		request_resource(res, &data_resource);
  	}
  	request_resource(&sysram_resources[0], &pdcdata_resource);
  }
  
  static int __init parisc_text_address(unsigned long vaddr)
  {
  	static unsigned long head_ptr __initdata;
  
  	if (!head_ptr)
  		head_ptr = PAGE_MASK & (unsigned long)
  			dereference_function_descriptor(&parisc_kernel_start);
  
  	return core_kernel_text(vaddr) || vaddr == head_ptr;
  }
  
  static void __init map_pages(unsigned long start_vaddr,
  			     unsigned long start_paddr, unsigned long size,
  			     pgprot_t pgprot, int force)
  {
  	pgd_t *pg_dir;
  	pmd_t *pmd;
  	pte_t *pg_table;
  	unsigned long end_paddr;
  	unsigned long start_pmd;
  	unsigned long start_pte;
  	unsigned long tmp1;
  	unsigned long tmp2;
  	unsigned long address;
  	unsigned long vaddr;
  	unsigned long ro_start;
  	unsigned long ro_end;
  	unsigned long kernel_end;
  
  	ro_start = __pa((unsigned long)_text);
  	ro_end   = __pa((unsigned long)&data_start);
  	kernel_end  = __pa((unsigned long)&_end);
  
  	end_paddr = start_paddr + size;
  
  	pg_dir = pgd_offset_k(start_vaddr);
  
  #if PTRS_PER_PMD == 1
  	start_pmd = 0;
  #else
  	start_pmd = ((start_vaddr >> PMD_SHIFT) & (PTRS_PER_PMD - 1));
  #endif
  	start_pte = ((start_vaddr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1));
  
  	address = start_paddr;
  	vaddr = start_vaddr;
  	while (address < end_paddr) {
  #if PTRS_PER_PMD == 1
  		pmd = (pmd_t *)__pa(pg_dir);
  #else
  		pmd = (pmd_t *)pgd_address(*pg_dir);
  
  		/*
  		 * pmd is physical at this point
  		 */
  
  		if (!pmd) {
  			pmd = (pmd_t *) get_memblock(PAGE_SIZE << PMD_ORDER);
  			pmd = (pmd_t *) __pa(pmd);
  		}
  
  		pgd_populate(NULL, pg_dir, __va(pmd));
  #endif
  		pg_dir++;
  
  		/* now change pmd to kernel virtual addresses */
  
  		pmd = (pmd_t *)__va(pmd) + start_pmd;
  		for (tmp1 = start_pmd; tmp1 < PTRS_PER_PMD; tmp1++, pmd++) {
  
  			/*
  			 * pg_table is physical at this point
  			 */
  
  			pg_table = (pte_t *)pmd_address(*pmd);
  			if (!pg_table) {
  				pg_table = (pte_t *) get_memblock(PAGE_SIZE);
  				pg_table = (pte_t *) __pa(pg_table);
  			}
  
  			pmd_populate_kernel(NULL, pmd, __va(pg_table));
  
  			/* now change pg_table to kernel virtual addresses */
  
  			pg_table = (pte_t *) __va(pg_table) + start_pte;
  			for (tmp2 = start_pte; tmp2 < PTRS_PER_PTE; tmp2++, pg_table++) {
  				pte_t pte;
  
  				if (force)
  					pte =  __mk_pte(address, pgprot);
  				else if (parisc_text_address(vaddr)) {
  					pte = __mk_pte(address, PAGE_KERNEL_EXEC);
  					if (address >= ro_start && address < kernel_end)
  						pte = pte_mkhuge(pte);
  				}
  				else
  #if defined(CONFIG_PARISC_PAGE_SIZE_4KB)
  				if (address >= ro_start && address < ro_end) {
  					pte = __mk_pte(address, PAGE_KERNEL_EXEC);
  					pte = pte_mkhuge(pte);
  				} else
  #endif
  				{
  					pte = __mk_pte(address, pgprot);
  					if (address >= ro_start && address < kernel_end)
  						pte = pte_mkhuge(pte);
  				}
  
  				if (address >= end_paddr) {
  					if (force)
  						break;
  					else
  						pte_val(pte) = 0;
  				}
  
  				set_pte(pg_table, pte);
  
  				address += PAGE_SIZE;
  				vaddr += PAGE_SIZE;
  			}
  			start_pte = 0;
  
  			if (address >= end_paddr)
  			    break;
  		}
  		start_pmd = 0;
  	}
  }
  
  void free_initmem(void)
  {
  	unsigned long init_begin = (unsigned long)__init_begin;
  	unsigned long init_end = (unsigned long)__init_end;
  
  	/* The init text pages are marked R-X.  We have to
  	 * flush the icache and mark them RW-
  	 *
  	 * This is tricky, because map_pages is in the init section.
  	 * Do a dummy remap of the data section first (the data
  	 * section is already PAGE_KERNEL) to pull in the TLB entries
  	 * for map_kernel */
  	map_pages(init_begin, __pa(init_begin), init_end - init_begin,
  		  PAGE_KERNEL_RWX, 1);
  	/* now remap at PAGE_KERNEL since the TLB is pre-primed to execute
  	 * map_pages */
  	map_pages(init_begin, __pa(init_begin), init_end - init_begin,
  		  PAGE_KERNEL, 1);
  
  	/* force the kernel to see the new TLB entries */
  	__flush_tlb_range(0, init_begin, init_end);
  
  	/* finally dump all the instructions which were cached, since the
  	 * pages are no-longer executable */
  	flush_icache_range(init_begin, init_end);
  	
  	free_initmem_default(POISON_FREE_INITMEM);
  
  	/* set up a new led state on systems shipped LED State panel */
  	pdc_chassis_send_status(PDC_CHASSIS_DIRECT_BCOMPLETE);
  }
  
  
  #ifdef CONFIG_STRICT_KERNEL_RWX
  void mark_rodata_ro(void)
  {
  	/* rodata memory was already mapped with KERNEL_RO access rights by
             pagetable_init() and map_pages(). No need to do additional stuff here */
  	printk (KERN_INFO "Write protecting the kernel read-only data: %luk\n",
  		(unsigned long)(__end_rodata - __start_rodata) >> 10);
  }
  #endif
  
  
  /*
   * Just an arbitrary offset to serve as a "hole" between mapping areas
   * (between top of physical memory and a potential pcxl dma mapping
   * area, and below the vmalloc mapping area).
   *
   * The current 32K value just means that there will be a 32K "hole"
   * between mapping areas. That means that  any out-of-bounds memory
   * accesses will hopefully be caught. The vmalloc() routines leaves
   * a hole of 4kB between each vmalloced area for the same reason.
   */
  
   /* Leave room for gateway page expansion */
  #if KERNEL_MAP_START < GATEWAY_PAGE_SIZE
  #error KERNEL_MAP_START is in gateway reserved region
  #endif
  #define MAP_START (KERNEL_MAP_START)
  
  #define VM_MAP_OFFSET  (32*1024)
  #define SET_MAP_OFFSET(x) ((void *)(((unsigned long)(x) + VM_MAP_OFFSET) \
  				     & ~(VM_MAP_OFFSET-1)))
  
  void *parisc_vmalloc_start __read_mostly;
  EXPORT_SYMBOL(parisc_vmalloc_start);
  
  #ifdef CONFIG_PA11
  unsigned long pcxl_dma_start __read_mostly;
  #endif
  
  void __init mem_init(void)
  {
  	/* Do sanity checks on IPC (compat) structures */
  	BUILD_BUG_ON(sizeof(struct ipc64_perm) != 48);
  #ifndef CONFIG_64BIT
  	BUILD_BUG_ON(sizeof(struct semid64_ds) != 80);
  	BUILD_BUG_ON(sizeof(struct msqid64_ds) != 104);
  	BUILD_BUG_ON(sizeof(struct shmid64_ds) != 104);
  #endif
  #ifdef CONFIG_COMPAT
  	BUILD_BUG_ON(sizeof(struct compat_ipc64_perm) != sizeof(struct ipc64_perm));
  	BUILD_BUG_ON(sizeof(struct compat_semid64_ds) != 80);
  	BUILD_BUG_ON(sizeof(struct compat_msqid64_ds) != 104);
  	BUILD_BUG_ON(sizeof(struct compat_shmid64_ds) != 104);
  #endif
  
  	/* Do sanity checks on page table constants */
  	BUILD_BUG_ON(PTE_ENTRY_SIZE != sizeof(pte_t));
  	BUILD_BUG_ON(PMD_ENTRY_SIZE != sizeof(pmd_t));
  	BUILD_BUG_ON(PGD_ENTRY_SIZE != sizeof(pgd_t));
  	BUILD_BUG_ON(PAGE_SHIFT + BITS_PER_PTE + BITS_PER_PMD + BITS_PER_PGD
  			> BITS_PER_LONG);
  
  	high_memory = __va((max_pfn << PAGE_SHIFT));
  	set_max_mapnr(page_to_pfn(virt_to_page(high_memory - 1)) + 1);
  	free_all_bootmem();
  
  #ifdef CONFIG_PA11
  	if (hppa_dma_ops == &pcxl_dma_ops) {
  		pcxl_dma_start = (unsigned long)SET_MAP_OFFSET(MAP_START);
  		parisc_vmalloc_start = SET_MAP_OFFSET(pcxl_dma_start
  						+ PCXL_DMA_MAP_SIZE);
  	} else {
  		pcxl_dma_start = 0;
  		parisc_vmalloc_start = SET_MAP_OFFSET(MAP_START);
  	}
  #else
  	parisc_vmalloc_start = SET_MAP_OFFSET(MAP_START);
  #endif
  
  	mem_init_print_info(NULL);
  #ifdef CONFIG_DEBUG_KERNEL /* double-sanity-check paranoia */
  	printk("virtual kernel memory layout:\n"
  	       "    vmalloc : 0x%p - 0x%p   (%4ld MB)\n"
  	       "    memory  : 0x%p - 0x%p   (%4ld MB)\n"
  	       "      .init : 0x%p - 0x%p   (%4ld kB)\n"
  	       "      .data : 0x%p - 0x%p   (%4ld kB)\n"
  	       "      .text : 0x%p - 0x%p   (%4ld kB)\n",
  
  	       (void*)VMALLOC_START, (void*)VMALLOC_END,
  	       (VMALLOC_END - VMALLOC_START) >> 20,
  
  	       __va(0), high_memory,
  	       ((unsigned long)high_memory - (unsigned long)__va(0)) >> 20,
  
  	       __init_begin, __init_end,
  	       ((unsigned long)__init_end - (unsigned long)__init_begin) >> 10,
  
  	       _etext, _edata,
  	       ((unsigned long)_edata - (unsigned long)_etext) >> 10,
  
  	       _text, _etext,
  	       ((unsigned long)_etext - (unsigned long)_text) >> 10);
  #endif
  }
  
  unsigned long *empty_zero_page __read_mostly;
  EXPORT_SYMBOL(empty_zero_page);
  
  /*
   * pagetable_init() sets up the page tables
   *
   * Note that gateway_init() places the Linux gateway page at page 0.
   * Since gateway pages cannot be dereferenced this has the desirable
   * side effect of trapping those pesky NULL-reference errors in the
   * kernel.
   */
  static void __init pagetable_init(void)
  {
  	int range;
  
  	/* Map each physical memory range to its kernel vaddr */
  
  	for (range = 0; range < npmem_ranges; range++) {
  		unsigned long start_paddr;
  		unsigned long end_paddr;
  		unsigned long size;
  
  		start_paddr = pmem_ranges[range].start_pfn << PAGE_SHIFT;
  		size = pmem_ranges[range].pages << PAGE_SHIFT;
  		end_paddr = start_paddr + size;
  
  		map_pages((unsigned long)__va(start_paddr), start_paddr,
  			  size, PAGE_KERNEL, 0);
  	}
  
  #ifdef CONFIG_BLK_DEV_INITRD
  	if (initrd_end && initrd_end > mem_limit) {
  		printk(KERN_INFO "initrd: mapping %08lx-%08lx\n", initrd_start, initrd_end);
  		map_pages(initrd_start, __pa(initrd_start),
  			  initrd_end - initrd_start, PAGE_KERNEL, 0);
  	}
  #endif
  
  	empty_zero_page = get_memblock(PAGE_SIZE);
  }
  
  static void __init gateway_init(void)
  {
  	unsigned long linux_gateway_page_addr;
  	/* FIXME: This is 'const' in order to trick the compiler
  	   into not treating it as DP-relative data. */
  	extern void * const linux_gateway_page;
  
  	linux_gateway_page_addr = LINUX_GATEWAY_ADDR & PAGE_MASK;
  
  	/*
  	 * Setup Linux Gateway page.
  	 *
  	 * The Linux gateway page will reside in kernel space (on virtual
  	 * page 0), so it doesn't need to be aliased into user space.
  	 */
  
  	map_pages(linux_gateway_page_addr, __pa(&linux_gateway_page),
  		  PAGE_SIZE, PAGE_GATEWAY, 1);
  }
  
  void __init paging_init(void)
  {
  	int i;
  
  	setup_bootmem();
  	pagetable_init();
  	gateway_init();
  	flush_cache_all_local(); /* start with known state */
  	flush_tlb_all_local(NULL);
  
  	for (i = 0; i < npmem_ranges; i++) {
  		unsigned long zones_size[MAX_NR_ZONES] = { 0, };
  
  		zones_size[ZONE_NORMAL] = pmem_ranges[i].pages;
  
  #ifdef CONFIG_DISCONTIGMEM
  		/* Need to initialize the pfnnid_map before we can initialize
  		   the zone */
  		{
  		    int j;
  		    for (j = (pmem_ranges[i].start_pfn >> PFNNID_SHIFT);
  			 j <= ((pmem_ranges[i].start_pfn + pmem_ranges[i].pages) >> PFNNID_SHIFT);
  			 j++) {
  			pfnnid_map[j] = i;
  		    }
  		}
  #endif
  
  		free_area_init_node(i, zones_size,
  				pmem_ranges[i].start_pfn, NULL);
  	}
  }
  
  #ifdef CONFIG_PA20
  
  /*
   * Currently, all PA20 chips have 18 bit protection IDs, which is the
   * limiting factor (space ids are 32 bits).
   */
  
  #define NR_SPACE_IDS 262144
  
  #else
  
  /*
   * Currently we have a one-to-one relationship between space IDs and
   * protection IDs. Older parisc chips (PCXS, PCXT, PCXL, PCXL2) only
   * support 15 bit protection IDs, so that is the limiting factor.
   * PCXT' has 18 bit protection IDs, but only 16 bit spaceids, so it's
   * probably not worth the effort for a special case here.
   */
  
  #define NR_SPACE_IDS 32768
  
  #endif  /* !CONFIG_PA20 */
  
  #define RECYCLE_THRESHOLD (NR_SPACE_IDS / 2)
  #define SID_ARRAY_SIZE  (NR_SPACE_IDS / (8 * sizeof(long)))
  
  static unsigned long space_id[SID_ARRAY_SIZE] = { 1 }; /* disallow space 0 */
  static unsigned long dirty_space_id[SID_ARRAY_SIZE];
  static unsigned long space_id_index;
  static unsigned long free_space_ids = NR_SPACE_IDS - 1;
  static unsigned long dirty_space_ids = 0;
  
  static DEFINE_SPINLOCK(sid_lock);
  
  unsigned long alloc_sid(void)
  {
  	unsigned long index;
  
  	spin_lock(&sid_lock);
  
  	if (free_space_ids == 0) {
  		if (dirty_space_ids != 0) {
  			spin_unlock(&sid_lock);
  			flush_tlb_all(); /* flush_tlb_all() calls recycle_sids() */
  			spin_lock(&sid_lock);
  		}
  		BUG_ON(free_space_ids == 0);
  	}
  
  	free_space_ids--;
  
  	index = find_next_zero_bit(space_id, NR_SPACE_IDS, space_id_index);
  	space_id[index >> SHIFT_PER_LONG] |= (1L << (index & (BITS_PER_LONG - 1)));
  	space_id_index = index;
  
  	spin_unlock(&sid_lock);
  
  	return index << SPACEID_SHIFT;
  }
  
  void free_sid(unsigned long spaceid)
  {
  	unsigned long index = spaceid >> SPACEID_SHIFT;
  	unsigned long *dirty_space_offset;
  
  	dirty_space_offset = dirty_space_id + (index >> SHIFT_PER_LONG);
  	index &= (BITS_PER_LONG - 1);
  
  	spin_lock(&sid_lock);
  
  	BUG_ON(*dirty_space_offset & (1L << index)); /* attempt to free space id twice */
  
  	*dirty_space_offset |= (1L << index);
  	dirty_space_ids++;
  
  	spin_unlock(&sid_lock);
  }
  
  
  #ifdef CONFIG_SMP
  static void get_dirty_sids(unsigned long *ndirtyptr,unsigned long *dirty_array)
  {
  	int i;
  
  	/* NOTE: sid_lock must be held upon entry */
  
  	*ndirtyptr = dirty_space_ids;
  	if (dirty_space_ids != 0) {
  	    for (i = 0; i < SID_ARRAY_SIZE; i++) {
  		dirty_array[i] = dirty_space_id[i];
  		dirty_space_id[i] = 0;
  	    }
  	    dirty_space_ids = 0;
  	}
  
  	return;
  }
  
  static void recycle_sids(unsigned long ndirty,unsigned long *dirty_array)
  {
  	int i;
  
  	/* NOTE: sid_lock must be held upon entry */
  
  	if (ndirty != 0) {
  		for (i = 0; i < SID_ARRAY_SIZE; i++) {
  			space_id[i] ^= dirty_array[i];
  		}
  
  		free_space_ids += ndirty;
  		space_id_index = 0;
  	}
  }
  
  #else /* CONFIG_SMP */
  
  static void recycle_sids(void)
  {
  	int i;
  
  	/* NOTE: sid_lock must be held upon entry */
  
  	if (dirty_space_ids != 0) {
  		for (i = 0; i < SID_ARRAY_SIZE; i++) {
  			space_id[i] ^= dirty_space_id[i];
  			dirty_space_id[i] = 0;
  		}
  
  		free_space_ids += dirty_space_ids;
  		dirty_space_ids = 0;
  		space_id_index = 0;
  	}
  }
  #endif
  
  /*
   * flush_tlb_all() calls recycle_sids(), since whenever the entire tlb is
   * purged, we can safely reuse the space ids that were released but
   * not flushed from the tlb.
   */
  
  #ifdef CONFIG_SMP
  
  static unsigned long recycle_ndirty;
  static unsigned long recycle_dirty_array[SID_ARRAY_SIZE];
  static unsigned int recycle_inuse;
  
  void flush_tlb_all(void)
  {
  	int do_recycle;
  
  	__inc_irq_stat(irq_tlb_count);
  	do_recycle = 0;
  	spin_lock(&sid_lock);
  	if (dirty_space_ids > RECYCLE_THRESHOLD) {
  	    BUG_ON(recycle_inuse);  /* FIXME: Use a semaphore/wait queue here */
  	    get_dirty_sids(&recycle_ndirty,recycle_dirty_array);
  	    recycle_inuse++;
  	    do_recycle++;
  	}
  	spin_unlock(&sid_lock);
  	on_each_cpu(flush_tlb_all_local, NULL, 1);
  	if (do_recycle) {
  	    spin_lock(&sid_lock);
  	    recycle_sids(recycle_ndirty,recycle_dirty_array);
  	    recycle_inuse = 0;
  	    spin_unlock(&sid_lock);
  	}
  }
  #else
  void flush_tlb_all(void)
  {
  	__inc_irq_stat(irq_tlb_count);
  	spin_lock(&sid_lock);
  	flush_tlb_all_local(NULL);
  	recycle_sids();
  	spin_unlock(&sid_lock);
  }
  #endif
  
  #ifdef CONFIG_BLK_DEV_INITRD
  void free_initrd_mem(unsigned long start, unsigned long end)
  {
  	free_reserved_area((void *)start, (void *)end, -1, "initrd");
  }
  #endif
  