/* sun4c.c: Doing in software what should be done in hardware.
 *
 * Copyright (C) 1996 David S. Miller (davem@davemloft.net)
 * Copyright (C) 1996 Eddie C. Dost (ecd@skynet.be)
 * Copyright (C) 1996 Andrew Tridgell (Andrew.Tridgell@anu.edu.au)
 * Copyright (C) 1997-2000 Anton Blanchard (anton@samba.org)
 * Copyright (C) 1998 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
 */

#define NR_TASK_BUCKETS 512

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/bootmem.h>
#include <linux/highmem.h>
#include <linux/fs.h>
#include <linux/seq_file.h>
#include <linux/scatterlist.h>
#include <linux/bitmap.h>

#include <asm/sections.h>
#include <asm/page.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/vaddrs.h>
#include <asm/idprom.h>
#include <asm/machines.h>
#include <asm/memreg.h>
#include <asm/processor.h>
#include <asm/auxio.h>
#include <asm/io.h>
#include <asm/oplib.h>
#include <asm/openprom.h>
#include <asm/mmu_context.h>
#include <asm/highmem.h>
#include <asm/btfixup.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>

/* Because of our dynamic kernel TLB miss strategy, and how
 * our DVMA mapping allocation works, you _MUST_:
 *
 * 1) Disable interrupts _and_ not touch any dynamic kernel
 *    memory while messing with kernel MMU state.  By
 *    dynamic memory I mean any object which is not in
 *    the kernel image itself or a thread_union (both of
 *    which are locked into the MMU).
 * 2) Disable interrupts while messing with user MMU state.
 */

extern int num_segmaps, num_contexts;

extern unsigned long page_kernel;

/* That's it, we prom_halt() on sun4c if the cache size is something other than 65536.
 * So let's save some cycles and just use that everywhere except for that bootup
 * sanity check.
 */
#define SUN4C_VAC_SIZE 65536

#define SUN4C_KERNEL_BUCKETS 32

/* Flushing the cache. */
struct sun4c_vac_props sun4c_vacinfo;
unsigned long sun4c_kernel_faults;

/* Invalidate every sun4c cache line tag. */
static void __init sun4c_flush_all(void)
{
	unsigned long begin, end;

	if (sun4c_vacinfo.on)
		panic("SUN4C: AIEEE, trying to invalidate vac while it is on.");

	/* Clear 'valid' bit in all cache line tags */
	begin = AC_CACHETAGS;
	end = (AC_CACHETAGS + SUN4C_VAC_SIZE);
	while (begin < end) {
		__asm__ __volatile__("sta %%g0, [%0] %1\n\t" : :
				     "r" (begin), "i" (ASI_CONTROL));
		begin += sun4c_vacinfo.linesize;
	}
}

static void sun4c_flush_context_hw(void)
{
	unsigned long end = SUN4C_VAC_SIZE;

	__asm__ __volatile__(
		"1:	addcc	%0, -4096, %0\n\t"
		"	bne	1b\n\t"
		"	 sta	%%g0, [%0] %2"
	: "=&r" (end)
	: "0" (end), "i" (ASI_HWFLUSHCONTEXT)
	: "cc");
}

/* Must be called minimally with IRQs disabled. */
static void sun4c_flush_segment_hw(unsigned long addr)
{
	if (sun4c_get_segmap(addr) != invalid_segment) {
		unsigned long vac_size = SUN4C_VAC_SIZE;

		__asm__ __volatile__(
			"1:	addcc	%0, -4096, %0\n\t"
			"	bne	1b\n\t"
			"	 sta	%%g0, [%2 + %0] %3"
			: "=&r" (vac_size)
			: "0" (vac_size), "r" (addr), "i" (ASI_HWFLUSHSEG)
			: "cc");
	}
}

/* File local boot time fixups. */
BTFIXUPDEF_CALL(void, sun4c_flush_page, unsigned long)
BTFIXUPDEF_CALL(void, sun4c_flush_segment, unsigned long)
BTFIXUPDEF_CALL(void, sun4c_flush_context, void)

#define sun4c_flush_page(addr) BTFIXUP_CALL(sun4c_flush_page)(addr)
#define sun4c_flush_segment(addr) BTFIXUP_CALL(sun4c_flush_segment)(addr)
#define sun4c_flush_context() BTFIXUP_CALL(sun4c_flush_context)()

/* Must be called minimally with interrupts disabled. */
static void sun4c_flush_page_hw(unsigned long addr)
{
	addr &= PAGE_MASK;
	if ((int)sun4c_get_pte(addr) < 0)
		__asm__ __volatile__("sta %%g0, [%0] %1"
				     : : "r" (addr), "i" (ASI_HWFLUSHPAGE));
}

/* Don't inline the software version as it eats too many cache lines if expanded. */
static void sun4c_flush_context_sw(void)
{
	unsigned long nbytes = SUN4C_VAC_SIZE;
	unsigned long lsize = sun4c_vacinfo.linesize;

	__asm__ __volatile__(
	"add	%2, %2, %%g1\n\t"
	"add	%2, %%g1, %%g2\n\t"
	"add	%2, %%g2, %%g3\n\t"
	"add	%2, %%g3, %%g4\n\t"
	"add	%2, %%g4, %%g5\n\t"
	"add	%2, %%g5, %%o4\n\t"
	"add	%2, %%o4, %%o5\n"
	"1:\n\t"
	"subcc	%0, %%o5, %0\n\t"
	"sta	%%g0, [%0] %3\n\t"
	"sta	%%g0, [%0 + %2] %3\n\t"
	"sta	%%g0, [%0 + %%g1] %3\n\t"
	"sta	%%g0, [%0 + %%g2] %3\n\t"
	"sta	%%g0, [%0 + %%g3] %3\n\t"
	"sta	%%g0, [%0 + %%g4] %3\n\t"
	"sta	%%g0, [%0 + %%g5] %3\n\t"
	"bg	1b\n\t"
	" sta	%%g0, [%1 + %%o4] %3\n"
	: "=&r" (nbytes)
	: "0" (nbytes), "r" (lsize), "i" (ASI_FLUSHCTX)
	: "g1", "g2", "g3", "g4", "g5", "o4", "o5", "cc");
}

/* Don't inline the software version as it eats too many cache lines if expanded. */
static void sun4c_flush_segment_sw(unsigned long addr)
{
	if (sun4c_get_segmap(addr) != invalid_segment) {
		unsigned long nbytes = SUN4C_VAC_SIZE;
		unsigned long lsize = sun4c_vacinfo.linesize;

		__asm__ __volatile__(
		"add	%2, %2, %%g1\n\t"
		"add	%2, %%g1, %%g2\n\t"
		"add	%2, %%g2, %%g3\n\t"
		"add	%2, %%g3, %%g4\n\t"
		"add	%2, %%g4, %%g5\n\t"
		"add	%2, %%g5, %%o4\n\t"
		"add	%2, %%o4, %%o5\n"
		"1:\n\t"
		"subcc	%1, %%o5, %1\n\t"
		"sta	%%g0, [%0] %6\n\t"
		"sta	%%g0, [%0 + %2] %6\n\t"
		"sta	%%g0, [%0 + %%g1] %6\n\t"
		"sta	%%g0, [%0 + %%g2] %6\n\t"
		"sta	%%g0, [%0 + %%g3] %6\n\t"
		"sta	%%g0, [%0 + %%g4] %6\n\t"
		"sta	%%g0, [%0 + %%g5] %6\n\t"
		"sta	%%g0, [%0 + %%o4] %6\n\t"
		"bg	1b\n\t"
		" add	%0, %%o5, %0\n"
		: "=&r" (addr), "=&r" (nbytes), "=&r" (lsize)
		: "0" (addr), "1" (nbytes), "2" (lsize),
		  "i" (ASI_FLUSHSEG)
		: "g1", "g2", "g3", "g4", "g5", "o4", "o5", "cc");
	}
}

/* Don't inline the software version as it eats too many cache lines if expanded. */
static void sun4c_flush_page_sw(unsigned long addr)
{
	addr &= PAGE_MASK;
	if ((sun4c_get_pte(addr) & (_SUN4C_PAGE_NOCACHE | _SUN4C_PAGE_VALID)) ==
	    _SUN4C_PAGE_VALID) {
		unsigned long left = PAGE_SIZE;
		unsigned long lsize = sun4c_vacinfo.linesize;

		__asm__ __volatile__(
		"add	%2, %2, %%g1\n\t"
		"add	%2, %%g1, %%g2\n\t"
		"add	%2, %%g2, %%g3\n\t"
		"add	%2, %%g3, %%g4\n\t"
		"add	%2, %%g4, %%g5\n\t"
		"add	%2, %%g5, %%o4\n\t"
		"add	%2, %%o4, %%o5\n"
		"1:\n\t"
		"subcc	%1, %%o5, %1\n\t"
		"sta	%%g0, [%0] %6\n\t"
		"sta	%%g0, [%0 + %2] %6\n\t"
		"sta	%%g0, [%0 + %%g1] %6\n\t"
		"sta	%%g0, [%0 + %%g2] %6\n\t"
		"sta	%%g0, [%0 + %%g3] %6\n\t"
		"sta	%%g0, [%0 + %%g4] %6\n\t"
		"sta	%%g0, [%0 + %%g5] %6\n\t"
		"sta	%%g0, [%0 + %%o4] %6\n\t"
		"bg	1b\n\t"
		" add	%0, %%o5, %0\n"
		: "=&r" (addr), "=&r" (left), "=&r" (lsize)
		: "0" (addr), "1" (left), "2" (lsize),
		  "i" (ASI_FLUSHPG)
		: "g1", "g2", "g3", "g4", "g5", "o4", "o5", "cc");
	}
}

/* The sun4c's do have an on chip store buffer.  And the way you
 * clear them out isn't so obvious.  The only way I can think of
 * to accomplish this is to read the current context register,
 * store the same value there, then read an external hardware
 * register.
 */
void sun4c_complete_all_stores(void)
{
	volatile int _unused;

	_unused = sun4c_get_context();
	sun4c_set_context(_unused);
	_unused = get_auxio();
}

/* Bootup utility functions. */
static inline void sun4c_init_clean_segmap(unsigned char pseg)
{
	unsigned long vaddr;

	sun4c_put_segmap(0, pseg);
	for (vaddr = 0; vaddr < SUN4C_REAL_PGDIR_SIZE; vaddr += PAGE_SIZE)
		sun4c_put_pte(vaddr, 0);
	sun4c_put_segmap(0, invalid_segment);
}

static inline void sun4c_init_clean_mmu(unsigned long kernel_end)
{
	unsigned long vaddr;
	unsigned char savectx, ctx;

	savectx = sun4c_get_context();
	for (ctx = 0; ctx < num_contexts; ctx++) {
		sun4c_set_context(ctx);
		for (vaddr = 0; vaddr < 0x20000000; vaddr += SUN4C_REAL_PGDIR_SIZE)
			sun4c_put_segmap(vaddr, invalid_segment);
		for (vaddr = 0xe0000000; vaddr < KERNBASE; vaddr += SUN4C_REAL_PGDIR_SIZE)
			sun4c_put_segmap(vaddr, invalid_segment);
		for (vaddr = kernel_end; vaddr < KADB_DEBUGGER_BEGVM; vaddr += SUN4C_REAL_PGDIR_SIZE)
			sun4c_put_segmap(vaddr, invalid_segment);
		for (vaddr = LINUX_OPPROM_ENDVM; vaddr; vaddr += SUN4C_REAL_PGDIR_SIZE)
			sun4c_put_segmap(vaddr, invalid_segment);
	}
	sun4c_set_context(savectx);
}

void __init sun4c_probe_vac(void)
{
	sun4c_disable_vac();

	if ((idprom->id_machtype == (SM_SUN4C | SM_4C_SS1)) ||
	    (idprom->id_machtype == (SM_SUN4C | SM_4C_SS1PLUS))) {
		/* PROM on SS1 lacks this info, to be super safe we
		 * hard code it here since this arch is cast in stone.
		 */
		sun4c_vacinfo.num_bytes = 65536;
		sun4c_vacinfo.linesize = 16;
	} else {
		sun4c_vacinfo.num_bytes =
		 prom_getintdefault(prom_root_node, "vac-size", 65536);
		sun4c_vacinfo.linesize =
		 prom_getintdefault(prom_root_node, "vac-linesize", 16);
	}
	sun4c_vacinfo.do_hwflushes =
	 prom_getintdefault(prom_root_node, "vac-hwflush", 0);

	if (sun4c_vacinfo.do_hwflushes == 0)
		sun4c_vacinfo.do_hwflushes =
		 prom_getintdefault(prom_root_node, "vac_hwflush", 0);

	if (sun4c_vacinfo.num_bytes != 65536) {
		prom_printf("WEIRD Sun4C VAC cache size, "
			    "tell sparclinux@vger.kernel.org");
		prom_halt();
	}

	switch (sun4c_vacinfo.linesize) {
	case 16:
		sun4c_vacinfo.log2lsize = 4;
		break;
	case 32:
		sun4c_vacinfo.log2lsize = 5;
		break;
	default:
		prom_printf("probe_vac: Didn't expect vac-linesize of %d, halting\n",
			    sun4c_vacinfo.linesize);
		prom_halt();
	}

	sun4c_flush_all();
	sun4c_enable_vac();
}

/* Patch instructions for the low level kernel fault handler. */
extern unsigned long invalid_segment_patch1, invalid_segment_patch1_ff;
extern unsigned long invalid_segment_patch2, invalid_segment_patch2_ff;
extern unsigned long invalid_segment_patch1_1ff, invalid_segment_patch2_1ff;
extern unsigned long num_context_patch1, num_context_patch1_16;
extern unsigned long num_context_patch2_16;
extern unsigned long vac_linesize_patch, vac_linesize_patch_32;
extern unsigned long vac_hwflush_patch1, vac_hwflush_patch1_on;
extern unsigned long vac_hwflush_patch2, vac_hwflush_patch2_on;

#define PATCH_INSN(src, dst) do {	\
		daddr = &(dst);		\
		iaddr = &(src);		\
		*daddr = *iaddr;	\
	} while (0)

static void __init patch_kernel_fault_handler(void)
{
	unsigned long *iaddr, *daddr;

	switch (num_segmaps) {
		case 128:
			/* Default, nothing to do. */
			break;
		case 256:
			PATCH_INSN(invalid_segment_patch1_ff,
				   invalid_segment_patch1);
			PATCH_INSN(invalid_segment_patch2_ff,
				   invalid_segment_patch2);
			break;
		case 512:
			PATCH_INSN(invalid_segment_patch1_1ff,
				   invalid_segment_patch1);
			PATCH_INSN(invalid_segment_patch2_1ff,
				   invalid_segment_patch2);
			break;
		default:
			prom_printf("Unhandled number of segmaps: %d\n",
				    num_segmaps);
			prom_halt();
	}
	switch (num_contexts) {
		case 8:
			/* Default, nothing to do. */
			break;
		case 16:
			PATCH_INSN(num_context_patch1_16,
				   num_context_patch1);
			break;
		default:
			prom_printf("Unhandled number of contexts: %d\n",
				    num_contexts);
			prom_halt();
	}

	if (sun4c_vacinfo.do_hwflushes != 0) {
		PATCH_INSN(vac_hwflush_patch1_on, vac_hwflush_patch1);
		PATCH_INSN(vac_hwflush_patch2_on, vac_hwflush_patch2);
	} else {
		switch (sun4c_vacinfo.linesize) {
		case 16:
			/* Default, nothing to do. */
			break;
		case 32:
			PATCH_INSN(vac_linesize_patch_32, vac_linesize_patch);
			break;
		default:
			prom_printf("Impossible VAC linesize %d, halting...\n",
				    sun4c_vacinfo.linesize);
			prom_halt();
		}
	}
}

static void __init sun4c_probe_mmu(void)
{
	if ((idprom->id_machtype == (SM_SUN4C | SM_4C_SS1)) ||
	    (idprom->id_machtype == (SM_SUN4C | SM_4C_SS1PLUS))) {
		/* Hardcode these just to be safe, PROM on SS1 does
		* not have this info available in the root node.
		*/
		num_segmaps = 128;
		num_contexts = 8;
	} else {
		num_segmaps =
		    prom_getintdefault(prom_root_node, "mmu-npmg", 128);
		num_contexts =
		    prom_getintdefault(prom_root_node, "mmu-nctx", 0x8);
	}
	patch_kernel_fault_handler();
}

volatile unsigned long __iomem *sun4c_memerr_reg = NULL;

void __init sun4c_probe_memerr_reg(void)
{
	phandle node;
	struct linux_prom_registers regs[1];

	node = prom_getchild(prom_root_node);
	node = prom_searchsiblings(prom_root_node, "memory-error");
	if (!node)
		return;
	if (prom_getproperty(node, "reg", (char *)regs, sizeof(regs)) <= 0)
		return;
	/* hmm I think regs[0].which_io is zero here anyways */
	sun4c_memerr_reg = ioremap(regs[0].phys_addr, regs[0].reg_size);
}

static inline void sun4c_init_ss2_cache_bug(void)
{
	if ((idprom->id_machtype == (SM_SUN4C | SM_4C_SS2)) ||
	    (idprom->id_machtype == (SM_SUN4C | SM_4C_IPX)) ||
	    (idprom->id_machtype == (SM_SUN4C | SM_4C_ELC))) {
		/* Whee.. */
		printk("SS2 cache bug detected, uncaching trap table page\n");
		sun4c_flush_page((unsigned int) &_start);
		sun4c_put_pte(((unsigned long) &_start),
			(sun4c_get_pte((unsigned long) &_start) | _SUN4C_PAGE_NOCACHE));
	}
}

/* Addr is always aligned on a page boundary for us already. */
static int sun4c_map_dma_area(struct device *dev, dma_addr_t *pba, unsigned long va,
			      unsigned long addr, int len)
{
	unsigned long page, end;

	*pba = addr;

	end = PAGE_ALIGN((addr + len));
	while (addr < end) {
		page = va;
		sun4c_flush_page(page);
		page -= PAGE_OFFSET;
		page >>= PAGE_SHIFT;
		page |= (_SUN4C_PAGE_VALID | _SUN4C_PAGE_DIRTY |
			 _SUN4C_PAGE_NOCACHE | _SUN4C_PAGE_PRIV);
		sun4c_put_pte(addr, page);
		addr += PAGE_SIZE;
		va += PAGE_SIZE;
	}

	return 0;
}

static void sun4c_unmap_dma_area(struct device *dev, unsigned long busa, int len)
{
	/* Fortunately for us, bus_addr == uncached_virt in sun4c. */
	/* XXX Implement this */
}

/* TLB management. */

/* Don't change this struct without changing entry.S. This is used
 * in the in-window kernel fault handler, and you don't want to mess
 * with that. (See sun4c_fault in entry.S).
 */
struct sun4c_mmu_entry {
	struct sun4c_mmu_entry *next;
	struct sun4c_mmu_entry *prev;
	unsigned long vaddr;
	unsigned char pseg;
	unsigned char locked;

	/* For user mappings only, and completely hidden from kernel
	 * TLB miss code.
	 */
	unsigned char ctx;
	struct sun4c_mmu_entry *lru_next;
	struct sun4c_mmu_entry *lru_prev;
};

static struct sun4c_mmu_entry mmu_entry_pool[SUN4C_MAX_SEGMAPS];

static void __init sun4c_init_mmu_entry_pool(void)
{
	int i;

	for (i=0; i < SUN4C_MAX_SEGMAPS; i++) {
		mmu_entry_pool[i].pseg = i;
		mmu_entry_pool[i].next = NULL;
		mmu_entry_pool[i].prev = NULL;
		mmu_entry_pool[i].vaddr = 0;
		mmu_entry_pool[i].locked = 0;
		mmu_entry_pool[i].ctx = 0;
		mmu_entry_pool[i].lru_next = NULL;
		mmu_entry_pool[i].lru_prev = NULL;
	}
	mmu_entry_pool[invalid_segment].locked = 1;
}

static inline void fix_permissions(unsigned long vaddr, unsigned long bits_on,
				   unsigned long bits_off)
{
	unsigned long start, end;

	end = vaddr + SUN4C_REAL_PGDIR_SIZE;
	for (start = vaddr; start < end; start += PAGE_SIZE)
		if (sun4c_get_pte(start) & _SUN4C_PAGE_VALID)
			sun4c_put_pte(start, (sun4c_get_pte(start) | bits_on) &
				      ~bits_off);
}

static inline void sun4c_init_map_kernelprom(unsigned long kernel_end)
{
	unsigned long vaddr;
	unsigned char pseg, ctx;

	for (vaddr = KADB_DEBUGGER_BEGVM;
	     vaddr < LINUX_OPPROM_ENDVM;
	     vaddr += SUN4C_REAL_PGDIR_SIZE) {
		pseg = sun4c_get_segmap(vaddr);
		if (pseg != invalid_segment) {
			mmu_entry_pool[pseg].locked = 1;
			for (ctx = 0; ctx < num_contexts; ctx++)
				prom_putsegment(ctx, vaddr, pseg);
			fix_permissions(vaddr, _SUN4C_PAGE_PRIV, 0);
		}
	}

	for (vaddr = KERNBASE; vaddr < kernel_end; vaddr += SUN4C_REAL_PGDIR_SIZE) {
		pseg = sun4c_get_segmap(vaddr);
		mmu_entry_pool[pseg].locked = 1;
		for (ctx = 0; ctx < num_contexts; ctx++)
			prom_putsegment(ctx, vaddr, pseg);
		fix_permissions(vaddr, _SUN4C_PAGE_PRIV, _SUN4C_PAGE_NOCACHE);
	}
}

static void __init sun4c_init_lock_area(unsigned long start, unsigned long end)
{
	int i, ctx;

	while (start < end) {
		for (i = 0; i < invalid_segment; i++)
			if (!mmu_entry_pool[i].locked)
				break;
		mmu_entry_pool[i].locked = 1;
		sun4c_init_clean_segmap(i);
		for (ctx = 0; ctx < num_contexts; ctx++)
			prom_putsegment(ctx, start, mmu_entry_pool[i].pseg);
		start += SUN4C_REAL_PGDIR_SIZE;
	}
}

/* Don't change this struct without changing entry.S. This is used
 * in the in-window kernel fault handler, and you don't want to mess
 * with that. (See sun4c_fault in entry.S).
 */
struct sun4c_mmu_ring {
	struct sun4c_mmu_entry ringhd;
	int num_entries;
};

static struct sun4c_mmu_ring sun4c_context_ring[SUN4C_MAX_CONTEXTS]; /* used user entries */
static struct sun4c_mmu_ring sun4c_ufree_ring;       /* free user entries */
static struct sun4c_mmu_ring sun4c_ulru_ring;	     /* LRU user entries */
struct sun4c_mmu_ring sun4c_kernel_ring;      /* used kernel entries */
struct sun4c_mmu_ring sun4c_kfree_ring;       /* free kernel entries */

static inline void sun4c_init_rings(void)
{
	int i;

	for (i = 0; i < SUN4C_MAX_CONTEXTS; i++) {
		sun4c_context_ring[i].ringhd.next =
			sun4c_context_ring[i].ringhd.prev =
			&sun4c_context_ring[i].ringhd;
		sun4c_context_ring[i].num_entries = 0;
	}
	sun4c_ufree_ring.ringhd.next = sun4c_ufree_ring.ringhd.prev =
		&sun4c_ufree_ring.ringhd;
	sun4c_ufree_ring.num_entries = 0;
	sun4c_ulru_ring.ringhd.lru_next = sun4c_ulru_ring.ringhd.lru_prev =
		&sun4c_ulru_ring.ringhd;
	sun4c_ulru_ring.num_entries = 0;
	sun4c_kernel_ring.ringhd.next = sun4c_kernel_ring.ringhd.prev =
		&sun4c_kernel_ring.ringhd;
	sun4c_kernel_ring.num_entries = 0;
	sun4c_kfree_ring.ringhd.next = sun4c_kfree_ring.ringhd.prev =
		&sun4c_kfree_ring.ringhd;
	sun4c_kfree_ring.num_entries = 0;
}

static void add_ring(struct sun4c_mmu_ring *ring,
		     struct sun4c_mmu_entry *entry)
{
	struct sun4c_mmu_entry *head = &ring->ringhd;

	entry->prev = head;
	(entry->next = head->next)->prev = entry;
	head->next = entry;
	ring->num_entries++;
}

static inline void add_lru(struct sun4c_mmu_entry *entry)
{
	struct sun4c_mmu_ring *ring = &sun4c_ulru_ring;
	struct sun4c_mmu_entry *head = &ring->ringhd;

	entry->lru_next = head;
	(entry->lru_prev = head->lru_prev)->lru_next = entry;
	head->lru_prev = entry;
}

static void add_ring_ordered(struct sun4c_mmu_ring *ring,
			     struct sun4c_mmu_entry *entry)
{
	struct sun4c_mmu_entry *head = &ring->ringhd;
	unsigned long addr = entry->vaddr;

	while ((head->next != &ring->ringhd) && (head->next->vaddr < addr))
		head = head->next;

	entry->prev = head;
	(entry->next = head->next)->prev = entry;
	head->next = entry;
	ring->num_entries++;

	add_lru(entry);
}

static inline void remove_ring(struct sun4c_mmu_ring *ring,
				   struct sun4c_mmu_entry *entry)
{
	struct sun4c_mmu_entry *next = entry->next;

	(next->prev = entry->prev)->next = next;
	ring->num_entries--;
}

static void remove_lru(struct sun4c_mmu_entry *entry)
{
	struct sun4c_mmu_entry *next = entry->lru_next;

	(next->lru_prev = entry->lru_prev)->lru_next = next;
}

static void free_user_entry(int ctx, struct sun4c_mmu_entry *entry)
{
        remove_ring(sun4c_context_ring+ctx, entry);
	remove_lru(entry);
        add_ring(&sun4c_ufree_ring, entry);
}

static void free_kernel_entry(struct sun4c_mmu_entry *entry,
			      struct sun4c_mmu_ring *ring)
{
        remove_ring(ring, entry);
        add_ring(&sun4c_kfree_ring, entry);
}

static void __init sun4c_init_fill_kernel_ring(int howmany)
{
	int i;

	while (howmany) {
		for (i = 0; i < invalid_segment; i++)
			if (!mmu_entry_pool[i].locked)
				break;
		mmu_entry_pool[i].locked = 1;
		sun4c_init_clean_segmap(i);
		add_ring(&sun4c_kfree_ring, &mmu_entry_pool[i]);
		howmany--;
	}
}

static void __init sun4c_init_fill_user_ring(void)
{
	int i;

	for (i = 0; i < invalid_segment; i++) {
		if (mmu_entry_pool[i].locked)
			continue;
		sun4c_init_clean_segmap(i);
		add_ring(&sun4c_ufree_ring, &mmu_entry_pool[i]);
	}
}

static void sun4c_kernel_unmap(struct sun4c_mmu_entry *kentry)
{
	int savectx, ctx;

	savectx = sun4c_get_context();
	for (ctx = 0; ctx < num_contexts; ctx++) {
		sun4c_set_context(ctx);
		sun4c_put_segmap(kentry->vaddr, invalid_segment);
	}
	sun4c_set_context(savectx);
}

static void sun4c_kernel_map(struct sun4c_mmu_entry *kentry)
{
	int savectx, ctx;

	savectx = sun4c_get_context();
	for (ctx = 0; ctx < num_contexts; ctx++) {
		sun4c_set_context(ctx);
		sun4c_put_segmap(kentry->vaddr, kentry->pseg);
	}
	sun4c_set_context(savectx);
}

#define sun4c_user_unmap(__entry) \
	sun4c_put_segmap((__entry)->vaddr, invalid_segment)

static void sun4c_demap_context(struct sun4c_mmu_ring *crp, unsigned char ctx)
{
	struct sun4c_mmu_entry *head = &crp->ringhd;
	unsigned long flags;

	local_irq_save(flags);
	if (head->next != head) {
		struct sun4c_mmu_entry *entry = head->next;
		int savectx = sun4c_get_context();

		flush_user_windows();
		sun4c_set_context(ctx);
		sun4c_flush_context();
		do {
			struct sun4c_mmu_entry *next = entry->next;

			sun4c_user_unmap(entry);
			free_user_entry(ctx, entry);

			entry = next;
		} while (entry != head);
		sun4c_set_context(savectx);
	}
	local_irq_restore(flags);
}

static int sun4c_user_taken_entries;  /* This is how much we have.             */
static int max_user_taken_entries;    /* This limits us and prevents deadlock. */

static struct sun4c_mmu_entry *sun4c_kernel_strategy(void)
{
	struct sun4c_mmu_entry *this_entry;

	/* If some are free, return first one. */
	if (sun4c_kfree_ring.num_entries) {
		this_entry = sun4c_kfree_ring.ringhd.next;
		return this_entry;
	}

	/* Else free one up. */
	this_entry = sun4c_kernel_ring.ringhd.prev;
	sun4c_flush_segment(this_entry->vaddr);
	sun4c_kernel_unmap(this_entry);
	free_kernel_entry(this_entry, &sun4c_kernel_ring);
	this_entry = sun4c_kfree_ring.ringhd.next;

	return this_entry;
}

/* Using this method to free up mmu entries eliminates a lot of
 * potential races since we have a kernel that incurs tlb
 * replacement faults.  There may be performance penalties.
 *
 * NOTE: Must be called with interrupts disabled.
 */
static struct sun4c_mmu_entry *sun4c_user_strategy(void)
{
	struct sun4c_mmu_entry *entry;
	unsigned char ctx;
	int savectx;

	/* If some are free, return first one. */
	if (sun4c_ufree_ring.num_entries) {
		entry = sun4c_ufree_ring.ringhd.next;
		goto unlink_out;
	}

	if (sun4c_user_taken_entries) {
		entry = sun4c_kernel_strategy();
		sun4c_user_taken_entries--;
		goto kunlink_out;
	}

	/* Grab from the beginning of the LRU list. */
	entry = sun4c_ulru_ring.ringhd.lru_next;
	ctx = entry->ctx;

	savectx = sun4c_get_context();
	flush_user_windows();
	sun4c_set_context(ctx);
	sun4c_flush_segment(entry->vaddr);
	sun4c_user_unmap(entry);
	remove_ring(sun4c_context_ring + ctx, entry);
	remove_lru(entry);
	sun4c_set_context(savectx);

	return entry;

unlink_out:
	remove_ring(&sun4c_ufree_ring, entry);
	return entry;
kunlink_out:
	remove_ring(&sun4c_kfree_ring, entry);
	return entry;
}

/* NOTE: Must be called with interrupts disabled. */
void sun4c_grow_kernel_ring(void)
{
	struct sun4c_mmu_entry *entry;

	/* Prevent deadlock condition. */
	if (sun4c_user_taken_entries >= max_user_taken_entries)
		return;

	if (sun4c_ufree_ring.num_entries) {
		entry = sun4c_ufree_ring.ringhd.next;
        	remove_ring(&sun4c_ufree_ring, entry);
		add_ring(&sun4c_kfree_ring, entry);
		sun4c_user_taken_entries++;
	}
}

/* 2 page buckets for task struct and kernel stack allocation.
 *
 * TASK_STACK_BEGIN
 * bucket[0]
 * bucket[1]
 *   [ ... ]
 * bucket[NR_TASK_BUCKETS-1]
 * TASK_STACK_BEGIN + (sizeof(struct task_bucket) * NR_TASK_BUCKETS)
 *
 * Each slot looks like:
 *
 *  page 1 --  task struct + beginning of kernel stack
 *  page 2 --  rest of kernel stack
 */

union task_union *sun4c_bucket[NR_TASK_BUCKETS];

static int sun4c_lowbucket_avail;

#define BUCKET_EMPTY     ((union task_union *) 0)
#define BUCKET_SHIFT     (PAGE_SHIFT + 1)        /* log2(sizeof(struct task_bucket)) */
#define BUCKET_SIZE      (1 << BUCKET_SHIFT)
#define BUCKET_NUM(addr) ((((addr) - SUN4C_LOCK_VADDR) >> BUCKET_SHIFT))
#define BUCKET_ADDR(num) (((num) << BUCKET_SHIFT) + SUN4C_LOCK_VADDR)
#define BUCKET_PTE(page)       \
        ((((page) - PAGE_OFFSET) >> PAGE_SHIFT) | pgprot_val(SUN4C_PAGE_KERNEL))
#define BUCKET_PTE_PAGE(pte)   \
        (PAGE_OFFSET + (((pte) & SUN4C_PFN_MASK) << PAGE_SHIFT))

static void get_locked_segment(unsigned long addr)
{
	struct sun4c_mmu_entry *stolen;
	unsigned long flags;

	local_irq_save(flags);
	addr &= SUN4C_REAL_PGDIR_MASK;
	stolen = sun4c_user_strategy();
	max_user_taken_entries--;
	stolen->vaddr = addr;
	flush_user_windows();
	sun4c_kernel_map(stolen);
	local_irq_restore(flags);
}

static void free_locked_segment(unsigned long addr)
{
	struct sun4c_mmu_entry *entry;
	unsigned long flags;
	unsigned char pseg;

	local_irq_save(flags);
	addr &= SUN4C_REAL_PGDIR_MASK;
	pseg = sun4c_get_segmap(addr);
	entry = &mmu_entry_pool[pseg];

	flush_user_windows();
	sun4c_flush_segment(addr);
	sun4c_kernel_unmap(entry);
	add_ring(&sun4c_ufree_ring, entry);
	max_user_taken_entries++;
	local_irq_restore(flags);
}

static inline void garbage_collect(int entry)
{
	int start, end;

	/* 32 buckets per segment... */
	entry &= ~31;
	start = entry;
	for (end = (start + 32); start < end; start++)
		if (sun4c_bucket[start] != BUCKET_EMPTY)
			return;

	/* Entire segment empty, release it. */
	free_locked_segment(BUCKET_ADDR(entry));
}

static struct thread_info *sun4c_alloc_thread_info_node(int node)
{
	unsigned long addr, pages;
	int entry;

	pages = __get_free_pages(GFP_KERNEL, THREAD_INFO_ORDER);
	if (!pages)
		return NULL;

	for (entry = sun4c_lowbucket_avail; entry < NR_TASK_BUCKETS; entry++)
		if (sun4c_bucket[entry] == BUCKET_EMPTY)
			break;
	if (entry == NR_TASK_BUCKETS) {
		free_pages(pages, THREAD_INFO_ORDER);
		return NULL;
	}
	if (entry >= sun4c_lowbucket_avail)
		sun4c_lowbucket_avail = entry + 1;

	addr = BUCKET_ADDR(entry);
	sun4c_bucket[entry] = (union task_union *) addr;
	if(sun4c_get_segmap(addr) == invalid_segment)
		get_locked_segment(addr);

	/* We are changing the virtual color of the page(s)
	 * so we must flush the cache to guarantee consistency.
	 */
	sun4c_flush_page(pages);
	sun4c_flush_page(pages + PAGE_SIZE);

	sun4c_put_pte(addr, BUCKET_PTE(pages));
	sun4c_put_pte(addr + PAGE_SIZE, BUCKET_PTE(pages + PAGE_SIZE));

#ifdef CONFIG_DEBUG_STACK_USAGE
	memset((void *)addr, 0, PAGE_SIZE << THREAD_INFO_ORDER);
#endif /* DEBUG_STACK_USAGE */

	return (struct thread_info *) addr;
}

static void sun4c_free_thread_info(struct thread_info *ti)
{
	unsigned long tiaddr = (unsigned long) ti;
	unsigned long pages = BUCKET_PTE_PAGE(sun4c_get_pte(tiaddr));
	int entry = BUCKET_NUM(tiaddr);

	/* We are deleting a mapping, so the flush here is mandatory. */
	sun4c_flush_page(tiaddr);
	sun4c_flush_page(tiaddr + PAGE_SIZE);

	sun4c_put_pte(tiaddr, 0);
	sun4c_put_pte(tiaddr + PAGE_SIZE, 0);

	sun4c_bucket[entry] = BUCKET_EMPTY;
	if (entry < sun4c_lowbucket_avail)
		sun4c_lowbucket_avail = entry;

	free_pages(pages, THREAD_INFO_ORDER);
	garbage_collect(entry);
}

static void __init sun4c_init_buckets(void)
{
	int entry;

	if (sizeof(union thread_union) != (PAGE_SIZE << THREAD_INFO_ORDER)) {
		extern void thread_info_size_is_bolixed_pete(void);
		thread_info_size_is_bolixed_pete();
	}

	for (entry = 0; entry < NR_TASK_BUCKETS; entry++)
		sun4c_bucket[entry] = BUCKET_EMPTY;
	sun4c_lowbucket_avail = 0;
}

static unsigned long sun4c_iobuffer_start;
static unsigned long sun4c_iobuffer_end;
static unsigned long sun4c_iobuffer_high;
static unsigned long *sun4c_iobuffer_map;
static int iobuffer_map_size;

/*
 * Alias our pages so they do not cause a trap.
 * Also one page may be aliased into several I/O areas and we may
 * finish these I/O separately.
 */
static char *sun4c_lockarea(char *vaddr, unsigned long size)
{
	unsigned long base, scan;
	unsigned long npages;
	unsigned long vpage;
	unsigned long pte;
	unsigned long apage;
	unsigned long high;
	unsigned long flags;

	npages = (((unsigned long)vaddr & ~PAGE_MASK) +
		  size + (PAGE_SIZE-1)) >> PAGE_SHIFT;

	local_irq_save(flags);
	base = bitmap_find_next_zero_area(sun4c_iobuffer_map, iobuffer_map_size,
						0, npages, 0);
	if (base >= iobuffer_map_size)
		goto abend;

	high = ((base + npages) << PAGE_SHIFT) + sun4c_iobuffer_start;
	high = SUN4C_REAL_PGDIR_ALIGN(high);
	while (high > sun4c_iobuffer_high) {
		get_locked_segment(sun4c_iobuffer_high);
		sun4c_iobuffer_high += SUN4C_REAL_PGDIR_SIZE;
	}

	vpage = ((unsigned long) vaddr) & PAGE_MASK;
	for (scan = base; scan < base+npages; scan++) {
		pte = ((vpage-PAGE_OFFSET) >> PAGE_SHIFT);
 		pte |= pgprot_val(SUN4C_PAGE_KERNEL);
		pte |= _SUN4C_PAGE_NOCACHE;
		set_bit(scan, sun4c_iobuffer_map);
		apage = (scan << PAGE_SHIFT) + sun4c_iobuffer_start;

		/* Flush original mapping so we see the right things later. */
		sun4c_flush_page(vpage);

		sun4c_put_pte(apage, pte);
		vpage += PAGE_SIZE;
	}
	local_irq_restore(flags);
	return (char *) ((base << PAGE_SHIFT) + sun4c_iobuffer_start +
			 (((unsigned long) vaddr) & ~PAGE_MASK));

abend:
	local_irq_restore(flags);
	printk("DMA vaddr=0x%p size=%08lx\n", vaddr, size);
	panic("Out of iobuffer table");
	return NULL;
}

static void sun4c_unlockarea(char *vaddr, unsigned long size)
{
	unsigned long vpage, npages;
	unsigned long flags;
	int scan, high;

	vpage = (unsigned long)vaddr & PAGE_MASK;
	npages = (((unsigned long)vaddr & ~PAGE_MASK) +
		  size + (PAGE_SIZE-1)) >> PAGE_SHIFT;

	local_irq_save(flags);
	while (npages != 0) {
		--npages;

		/* This mapping is marked non-cachable, no flush necessary. */
		sun4c_put_pte(vpage, 0);
		clear_bit((vpage - sun4c_iobuffer_start) >> PAGE_SHIFT,
			  sun4c_iobuffer_map);
		vpage += PAGE_SIZE;
	}

	/* garbage collect */
	scan = (sun4c_iobuffer_high - sun4c_iobuffer_start) >> PAGE_SHIFT;
	while (scan >= 0 && !sun4c_iobuffer_map[scan >> 5])
		scan -= 32;
	scan += 32;
	high = sun4c_iobuffer_start + (scan << PAGE_SHIFT);
	high = SUN4C_REAL_PGDIR_ALIGN(high) + SUN4C_REAL_PGDIR_SIZE;
	while (high < sun4c_iobuffer_high) {
		sun4c_iobuffer_high -= SUN4C_REAL_PGDIR_SIZE;
		free_locked_segment(sun4c_iobuffer_high);
	}
	local_irq_restore(flags);
}

/* Note the scsi code at init time passes to here buffers
 * which sit on the kernel stack, those are already locked
 * by implication and fool the page locking code above
 * if passed to by mistake.
 */
static __u32 sun4c_get_scsi_one(struct device *dev, char *bufptr, unsigned long len)
{
	unsigned long page;

	page = ((unsigned long)bufptr) & PAGE_MASK;
	if (!virt_addr_valid(page)) {
		sun4c_flush_page(page);
		return (__u32)bufptr; /* already locked */
	}
	return (__u32)sun4c_lockarea(bufptr, len);
}

static void sun4c_get_scsi_sgl(struct device *dev, struct scatterlist *sg, int sz)
{
	while (sz != 0) {
		--sz;
		sg->dma_address = (__u32)sun4c_lockarea(sg_virt(sg), sg->length);
		sg->dma_length = sg->length;
		sg = sg_next(sg);
	}
}

static void sun4c_release_scsi_one(struct device *dev, __u32 bufptr, unsigned long len)
{
	if (bufptr < sun4c_iobuffer_start)
		return; /* On kernel stack or similar, see above */
	sun4c_unlockarea((char *)bufptr, len);
}

static void sun4c_release_scsi_sgl(struct device *dev, struct scatterlist *sg, int sz)
{
	while (sz != 0) {
		--sz;
		sun4c_unlockarea((char *)sg->dma_address, sg->length);
		sg = sg_next(sg);
	}
}

#define TASK_ENTRY_SIZE    BUCKET_SIZE /* see above */
#define LONG_ALIGN(x) (((x)+(sizeof(long))-1)&~((sizeof(long))-1))

struct vm_area_struct sun4c_kstack_vma;

static void __init sun4c_init_lock_areas(void)
{
	unsigned long sun4c_taskstack_start;
	unsigned long sun4c_taskstack_end;
	int bitmap_size;

	sun4c_init_buckets();
	sun4c_taskstack_start = SUN4C_LOCK_VADDR;
	sun4c_taskstack_end = (sun4c_taskstack_start +
			       (TASK_ENTRY_SIZE * NR_TASK_BUCKETS));
	if (sun4c_taskstack_end >= SUN4C_LOCK_END) {
		prom_printf("Too many tasks, decrease NR_TASK_BUCKETS please.\n");
		prom_halt();
	}

	sun4c_iobuffer_start = sun4c_iobuffer_high =
				SUN4C_REAL_PGDIR_ALIGN(sun4c_taskstack_end);
	sun4c_iobuffer_end = SUN4C_LOCK_END;
	bitmap_size = (sun4c_iobuffer_end - sun4c_iobuffer_start) >> PAGE_SHIFT;
	bitmap_size = (bitmap_size + 7) >> 3;
	bitmap_size = LONG_ALIGN(bitmap_size);
	iobuffer_map_size = bitmap_size << 3;
	sun4c_iobuffer_map = __alloc_bootmem(bitmap_size, SMP_CACHE_BYTES, 0UL);
	memset((void *) sun4c_iobuffer_map, 0, bitmap_size);

	sun4c_kstack_vma.vm_mm = &init_mm;
	sun4c_kstack_vma.vm_start = sun4c_taskstack_start;
	sun4c_kstack_vma.vm_end = sun4c_taskstack_end;
	sun4c_kstack_vma.vm_page_prot = PAGE_SHARED;
	sun4c_kstack_vma.vm_flags = VM_READ | VM_WRITE | VM_EXEC;
	insert_vm_struct(&init_mm, &sun4c_kstack_vma);
}

/* Cache flushing on the sun4c. */
static void sun4c_flush_cache_all(void)
{
	unsigned long begin, end;

	flush_user_windows();
	begin = (KERNBASE + SUN4C_REAL_PGDIR_SIZE);
	end = (begin + SUN4C_VAC_SIZE);

	if (sun4c_vacinfo.linesize == 32) {
		while (begin < end) {
			__asm__ __volatile__(
			"ld	[%0 + 0x00], %%g0\n\t"
			"ld	[%0 + 0x20], %%g0\n\t"
			"ld	[%0 + 0x40], %%g0\n\t"
			"ld	[%0 + 0x60], %%g0\n\t"
			"ld	[%0 + 0x80], %%g0\n\t"
			"ld	[%0 + 0xa0], %%g0\n\t"
			"ld	[%0 + 0xc0], %%g0\n\t"
			"ld	[%0 + 0xe0], %%g0\n\t"
			"ld	[%0 + 0x100], %%g0\n\t"
			"ld	[%0 + 0x120], %%g0\n\t"
			"ld	[%0 + 0x140], %%g0\n\t"
			"ld	[%0 + 0x160], %%g0\n\t"
			"ld	[%0 + 0x180], %%g0\n\t"
			"ld	[%0 + 0x1a0], %%g0\n\t"
			"ld	[%0 + 0x1c0], %%g0\n\t"
			"ld	[%0 + 0x1e0], %%g0\n"
			: : "r" (begin));
			begin += 512;
		}
	} else {
		while (begin < end) {
			__asm__ __volatile__(
			"ld	[%0 + 0x00], %%g0\n\t"
			"ld	[%0 + 0x10], %%g0\n\t"
			"ld	[%0 + 0x20], %%g0\n\t"
			"ld	[%0 + 0x30], %%g0\n\t"
			"ld	[%0 + 0x40], %%g0\n\t"
			"ld	[%0 + 0x50], %%g0\n\t"
			"ld	[%0 + 0x60], %%g0\n\t"
			"ld	[%0 + 0x70], %%g0\n\t"
			"ld	[%0 + 0x80], %%g0\n\t"
			"ld	[%0 + 0x90], %%g0\n\t"
			"ld	[%0 + 0xa0], %%g0\n\t"
			"ld	[%0 + 0xb0], %%g0\n\t"
			"ld	[%0 + 0xc0], %%g0\n\t"
			"ld	[%0 + 0xd0], %%g0\n\t"
			"ld	[%0 + 0xe0], %%g0\n\t"
			"ld	[%0 + 0xf0], %%g0\n"
			: : "r" (begin));
			begin += 256;
		}
	}
}

static void sun4c_flush_cache_mm(struct mm_struct *mm)
{
	int new_ctx = mm->context;

	if (new_ctx != NO_CONTEXT) {
		flush_user_windows();

		if (sun4c_context_ring[new_ctx].num_entries) {
			struct sun4c_mmu_entry *head = &sun4c_context_ring[new_ctx].ringhd;
			unsigned long flags;

			local_irq_save(flags);
			if (head->next != head) {
				struct sun4c_mmu_entry *entry = head->next;
				int savectx = sun4c_get_context();

				sun4c_set_context(new_ctx);
				sun4c_flush_context();
				do {
					struct sun4c_mmu_entry *next = entry->next;

					sun4c_user_unmap(entry);
					free_user_entry(new_ctx, entry);

					entry = next;
				} while (entry != head);
				sun4c_set_context(savectx);
			}
			local_irq_restore(flags);
		}
	}
}

static void sun4c_flush_cache_range(struct vm_area_struct *vma, unsigned long start, unsigned long end)
{
	struct mm_struct *mm = vma->vm_mm;
	int new_ctx = mm->context;

	if (new_ctx != NO_CONTEXT) {
		struct sun4c_mmu_entry *head = &sun4c_context_ring[new_ctx].ringhd;
		struct sun4c_mmu_entry *entry;
		unsigned long flags;

		flush_user_windows();

		local_irq_save(flags);
		/* All user segmap chains are ordered on entry->vaddr. */
		for (entry = head->next;
		     (entry != head) && ((entry->vaddr+SUN4C_REAL_PGDIR_SIZE) < start);
		     entry = entry->next)
			;

		/* Tracing various job mixtures showed that this conditional
		 * only passes ~35% of the time for most worse case situations,
		 * therefore we avoid all of this gross overhead ~65% of the time.
		 */
		if ((entry != head) && (entry->vaddr < end)) {
			int octx = sun4c_get_context();
			sun4c_set_context(new_ctx);

			/* At this point, always, (start >= entry->vaddr) and
			 * (entry->vaddr < end), once the latter condition
			 * ceases to hold, or we hit the end of the list, we
			 * exit the loop.  The ordering of all user allocated
			 * segmaps makes this all work out so beautifully.
			 */
			do {
				struct sun4c_mmu_entry *next = entry->next;
				unsigned long realend;

				/* "realstart" is always >= entry->vaddr */
				realend = entry->vaddr + SUN4C_REAL_PGDIR_SIZE;
				if (end < realend)
					realend = end;
				if ((realend - entry->vaddr) <= (PAGE_SIZE << 3)) {
					unsigned long page = entry->vaddr;
					while (page < realend) {
						sun4c_flush_page(page);
						page += PAGE_SIZE;
					}
				} else {
					sun4c_flush_segment(entry->vaddr);
					sun4c_user_unmap(entry);
					free_user_entry(new_ctx, entry);
				}
				entry = next;
			} while ((entry != head) && (entry->vaddr < end));
			sun4c_set_context(octx);
		}
		local_irq_restore(flags);
	}
}

static void sun4c_flush_cache_page(struct vm_area_struct *vma, unsigned long page)
{
	struct mm_struct *mm = vma->vm_mm;
	int new_ctx = mm->context;

	/* Sun4c has no separate I/D caches so cannot optimize for non
	 * text page flushes.
	 */
	if (new_ctx != NO_CONTEXT) {
		int octx = sun4c_get_context();
		unsigned long flags;

		flush_user_windows();
		local_irq_save(flags);
		sun4c_set_context(new_ctx);
		sun4c_flush_page(page);
		sun4c_set_context(octx);
		local_irq_restore(flags);
	}
}

static void sun4c_flush_page_to_ram(unsigned long page)
{
	unsigned long flags;

	local_irq_save(flags);
	sun4c_flush_page(page);
	local_irq_restore(flags);
}

/* Sun4c cache is unified, both instructions and data live there, so
 * no need to flush the on-stack instructions for new signal handlers.
 */
static void sun4c_flush_sig_insns(struct mm_struct *mm, unsigned long insn_addr)
{
}

/* TLB flushing on the sun4c.  These routines count on the cache
 * flushing code to flush the user register windows so that we need
 * not do so when we get here.
 */

static void sun4c_flush_tlb_all(void)
{
	struct sun4c_mmu_entry *this_entry, *next_entry;
	unsigned long flags;
	int savectx, ctx;

	local_irq_save(flags);
	this_entry = sun4c_kernel_ring.ringhd.next;
	savectx = sun4c_get_context();
	flush_user_windows();
	while (sun4c_kernel_ring.num_entries) {
		next_entry = this_entry->next;
		sun4c_flush_segment(this_entry->vaddr);
		for (ctx = 0; ctx < num_contexts; ctx++) {
			sun4c_set_context(ctx);
			sun4c_put_segmap(this_entry->vaddr, invalid_segment);
		}
		free_kernel_entry(this_entry, &sun4c_kernel_ring);
		this_entry = next_entry;
	}
	sun4c_set_context(savectx);
	local_irq_restore(flags);
}

static void sun4c_flush_tlb_mm(struct mm_struct *mm)
{
	int new_ctx = mm->context;

	if (new_ctx != NO_CONTEXT) {
		struct sun4c_mmu_entry *head = &sun4c_context_ring[new_ctx].ringhd;
		unsigned long flags;

		local_irq_save(flags);
		if (head->next != head) {
			struct sun4c_mmu_entry *entry = head->next;
			int savectx = sun4c_get_context();

			sun4c_set_context(new_ctx);
			sun4c_flush_context();
			do {
				struct sun4c_mmu_entry *next = entry->next;

				sun4c_user_unmap(entry);
				free_user_entry(new_ctx, entry);

				entry = next;
			} while (entry != head);
			sun4c_set_context(savectx);
		}
		local_irq_restore(flags);
	}
}

static void sun4c_flush_tlb_range(struct vm_area_struct *vma, unsigned long start, unsigned long end)
{
	struct mm_struct *mm = vma->vm_mm;
	int new_ctx = mm->context;

	if (new_ctx != NO_CONTEXT) {
		struct sun4c_mmu_entry *head = &sun4c_context_ring[new_ctx].ringhd;
		struct sun4c_mmu_entry *entry;
		unsigned long flags;

		local_irq_save(flags);
		/* See commentary in sun4c_flush_cache_range(). */
		for (entry = head->next;
		     (entry != head) && ((entry->vaddr+SUN4C_REAL_PGDIR_SIZE) < start);
		     entry = entry->next)
			;

		if ((entry != head) && (entry->vaddr < end)) {
			int octx = sun4c_get_context();

			sun4c_set_context(new_ctx);
			do {
				struct sun4c_mmu_entry *next = entry->next;

				sun4c_flush_segment(entry->vaddr);
				sun4c_user_unmap(entry);
				free_user_entry(new_ctx, entry);

				entry = next;
			} while ((entry != head) && (entry->vaddr < end));
			sun4c_set_context(octx);
		}
		local_irq_restore(flags);
	}
}

static void sun4c_flush_tlb_page(struct vm_area_struct *vma, unsigned long page)
{
	struct mm_struct *mm = vma->vm_mm;
	int new_ctx = mm->context;

	if (new_ctx != NO_CONTEXT) {
		int savectx = sun4c_get_context();
		unsigned long flags;

		local_irq_save(flags);
		sun4c_set_context(new_ctx);
		page &= PAGE_MASK;
		sun4c_flush_page(page);
		sun4c_put_pte(page, 0);
		sun4c_set_context(savectx);
		local_irq_restore(flags);
	}
}

static inline void sun4c_mapioaddr(unsigned long physaddr, unsigned long virt_addr)
{
	unsigned long page_entry, pg_iobits;

	pg_iobits = _SUN4C_PAGE_PRESENT | _SUN4C_READABLE | _SUN4C_WRITEABLE |
		    _SUN4C_PAGE_IO | _SUN4C_PAGE_NOCACHE;

	page_entry = ((physaddr >> PAGE_SHIFT) & SUN4C_PFN_MASK);
	page_entry |= ((pg_iobits | _SUN4C_PAGE_PRIV) & ~(_SUN4C_PAGE_PRESENT));
	sun4c_put_pte(virt_addr, page_entry);
}

static void sun4c_mapiorange(unsigned int bus, unsigned long xpa,
    unsigned long xva, unsigned int len)
{
	while (len != 0) {
		len -= PAGE_SIZE;
		sun4c_mapioaddr(xpa, xva);
		xva += PAGE_SIZE;
		xpa += PAGE_SIZE;
	}
}

static void sun4c_unmapiorange(unsigned long virt_addr, unsigned int len)
{
	while (len != 0) {
		len -= PAGE_SIZE;
		sun4c_put_pte(virt_addr, 0);
		virt_addr += PAGE_SIZE;
	}
}

static void sun4c_alloc_context(struct mm_struct *old_mm, struct mm_struct *mm)
{
	struct ctx_list *ctxp;

	ctxp = ctx_free.next;
	if (ctxp != &ctx_free) {
		remove_from_ctx_list(ctxp);
		add_to_used_ctxlist(ctxp);
		mm->context = ctxp->ctx_number;
		ctxp->ctx_mm = mm;
		return;
	}
	ctxp = ctx_used.next;
	if (ctxp->ctx_mm == old_mm)
		ctxp = ctxp->next;
	remove_from_ctx_list(ctxp);
	add_to_used_ctxlist(ctxp);
	ctxp->ctx_mm->context = NO_CONTEXT;
	ctxp->ctx_mm = mm;
	mm->context = ctxp->ctx_number;
	sun4c_demap_context(&sun4c_context_ring[ctxp->ctx_number],
			       ctxp->ctx_number);
}

/* Switch the current MM context. */
static void sun4c_switch_mm(struct mm_struct *old_mm, struct mm_struct *mm, struct task_struct *tsk, int cpu)
{
	struct ctx_list *ctx;
	int dirty = 0;

	if (mm->context == NO_CONTEXT) {
		dirty = 1;
		sun4c_alloc_context(old_mm, mm);
	} else {
		/* Update the LRU ring of contexts. */
		ctx = ctx_list_pool + mm->context;
		remove_from_ctx_list(ctx);
		add_to_used_ctxlist(ctx);
	}
	if (dirty || old_mm != mm)
		sun4c_set_context(mm->context);
}

static void sun4c_destroy_context(struct mm_struct *mm)
{
	struct ctx_list *ctx_old;

	if (mm->context != NO_CONTEXT) {
		sun4c_demap_context(&sun4c_context_ring[mm->context], mm->context);
		ctx_old = ctx_list_pool + mm->context;
		remove_from_ctx_list(ctx_old);
		add_to_free_ctxlist(ctx_old);
		mm->context = NO_CONTEXT;
	}
}

static void sun4c_mmu_info(struct seq_file *m)
{
	int used_user_entries, i;

	used_user_entries = 0;
	for (i = 0; i < num_contexts; i++)
		used_user_entries += sun4c_context_ring[i].num_entries;

	seq_printf(m, 
		   "vacsize\t\t: %d bytes\n"
		   "vachwflush\t: %s\n"
		   "vaclinesize\t: %d bytes\n"
		   "mmuctxs\t\t: %d\n"
		   "mmupsegs\t: %d\n"
		   "kernelpsegs\t: %d\n"
		   "kfreepsegs\t: %d\n"
		   "usedpsegs\t: %d\n"
		   "ufreepsegs\t: %d\n"
		   "user_taken\t: %d\n"
		   "max_taken\t: %d\n",
		   sun4c_vacinfo.num_bytes,
		   (sun4c_vacinfo.do_hwflushes ? "yes" : "no"),
		   sun4c_vacinfo.linesize,
		   num_contexts,
		   (invalid_segment + 1),
		   sun4c_kernel_ring.num_entries,
		   sun4c_kfree_ring.num_entries,
		   used_user_entries,
		   sun4c_ufree_ring.num_entries,
		   sun4c_user_taken_entries,
		   max_user_taken_entries);
}

/* Nothing below here should touch the mmu hardware nor the mmu_entry
 * data structures.
 */

/* First the functions which the mid-level code uses to directly
 * manipulate the software page tables.  Some defines since we are
 * emulating the i386 page directory layout.
 */
#define PGD_PRESENT  0x001
#define PGD_RW       0x002
#define PGD_USER     0x004
#define PGD_ACCESSED 0x020
#define PGD_DIRTY    0x040
#define PGD_TABLE    (PGD_PRESENT | PGD_RW | PGD_USER | PGD_ACCESSED | PGD_DIRTY)

static void sun4c_set_pte(pte_t *ptep, pte_t pte)
{
	*ptep = pte;
}

static void sun4c_pgd_set(pgd_t * pgdp, pmd_t * pmdp)
{
}

static void sun4c_pmd_set(pmd_t * pmdp, pte_t * ptep)
{
	pmdp->pmdv[0] = PGD_TABLE | (unsigned long) ptep;
}

static void sun4c_pmd_populate(pmd_t * pmdp, struct page * ptep)
{
	if (page_address(ptep) == NULL) BUG();	/* No highmem on sun4c */
	pmdp->pmdv[0] = PGD_TABLE | (unsigned long) page_address(ptep);
}

static int sun4c_pte_present(pte_t pte)
{
	return ((pte_val(pte) & (_SUN4C_PAGE_PRESENT | _SUN4C_PAGE_PRIV)) != 0);
}
static void sun4c_pte_clear(pte_t *ptep)	{ *ptep = __pte(0); }

static int sun4c_pmd_bad(pmd_t pmd)
{
	return (((pmd_val(pmd) & ~PAGE_MASK) != PGD_TABLE) ||
		(!virt_addr_valid(pmd_val(pmd))));
}

static int sun4c_pmd_present(pmd_t pmd)
{
	return ((pmd_val(pmd) & PGD_PRESENT) != 0);
}

#if 0 /* if PMD takes one word */
static void sun4c_pmd_clear(pmd_t *pmdp)	{ *pmdp = __pmd(0); }
#else /* if pmd_t is a longish aggregate */
static void sun4c_pmd_clear(pmd_t *pmdp) {
	memset((void *)pmdp, 0, sizeof(pmd_t));
}
#endif

static int sun4c_pgd_none(pgd_t pgd)		{ return 0; }
static int sun4c_pgd_bad(pgd_t pgd)		{ return 0; }
static int sun4c_pgd_present(pgd_t pgd)	        { return 1; }
static void sun4c_pgd_clear(pgd_t * pgdp)	{ }

/*
 * The following only work if pte_present() is true.
 * Undefined behaviour if not..
 */
static pte_t sun4c_pte_mkwrite(pte_t pte)
{
	pte = __pte(pte_val(pte) | _SUN4C_PAGE_WRITE);
	if (pte_val(pte) & _SUN4C_PAGE_MODIFIED)
		pte = __pte(pte_val(pte) | _SUN4C_PAGE_SILENT_WRITE);
	return pte;
}

static pte_t sun4c_pte_mkdirty(pte_t pte)
{
	pte = __pte(pte_val(pte) | _SUN4C_PAGE_MODIFIED);
	if (pte_val(pte) & _SUN4C_PAGE_WRITE)
		pte = __pte(pte_val(pte) | _SUN4C_PAGE_SILENT_WRITE);
	return pte;
}

static pte_t sun4c_pte_mkyoung(pte_t pte)
{
	pte = __pte(pte_val(pte) | _SUN4C_PAGE_ACCESSED);
	if (pte_val(pte) & _SUN4C_PAGE_READ)
		pte = __pte(pte_val(pte) | _SUN4C_PAGE_SILENT_READ);
	return pte;
}

/*
 * Conversion functions: convert a page and protection to a page entry,
 * and a page entry and page directory to the page they refer to.
 */
static pte_t sun4c_mk_pte(struct page *page, pgprot_t pgprot)
{
	return __pte(page_to_pfn(page) | pgprot_val(pgprot));
}

static pte_t sun4c_mk_pte_phys(unsigned long phys_page, pgprot_t pgprot)
{
	return __pte((phys_page >> PAGE_SHIFT) | pgprot_val(pgprot));
}

static pte_t sun4c_mk_pte_io(unsigned long page, pgprot_t pgprot, int space)
{
	return __pte(((page - PAGE_OFFSET) >> PAGE_SHIFT) | pgprot_val(pgprot));
}

static unsigned long sun4c_pte_pfn(pte_t pte)
{
	return pte_val(pte) & SUN4C_PFN_MASK;
}

static pte_t sun4c_pgoff_to_pte(unsigned long pgoff)
{
	return __pte(pgoff | _SUN4C_PAGE_FILE);
}

static unsigned long sun4c_pte_to_pgoff(pte_t pte)
{
	return pte_val(pte) & ((1UL << PTE_FILE_MAX_BITS) - 1);
}


static inline unsigned long sun4c_pmd_page_v(pmd_t pmd)
{
	return (pmd_val(pmd) & PAGE_MASK);
}

static struct page *sun4c_pmd_page(pmd_t pmd)
{
	return virt_to_page(sun4c_pmd_page_v(pmd));
}

static unsigned long sun4c_pgd_page(pgd_t pgd) { return 0; }

/* to find an entry in a page-table-directory */
static inline pgd_t *sun4c_pgd_offset(struct mm_struct * mm, unsigned long address)
{
	return mm->pgd + (address >> SUN4C_PGDIR_SHIFT);
}

/* Find an entry in the second-level page table.. */
static pmd_t *sun4c_pmd_offset(pgd_t * dir, unsigned long address)
{
	return (pmd_t *) dir;
}

/* Find an entry in the third-level page table.. */ 
pte_t *sun4c_pte_offset_kernel(pmd_t * dir, unsigned long address)
{
	return (pte_t *) sun4c_pmd_page_v(*dir) +
			((address >> PAGE_SHIFT) & (SUN4C_PTRS_PER_PTE - 1));
}

static unsigned long sun4c_swp_type(swp_entry_t entry)
{
	return (entry.val & SUN4C_SWP_TYPE_MASK);
}

static unsigned long sun4c_swp_offset(swp_entry_t entry)
{
	return (entry.val >> SUN4C_SWP_OFF_SHIFT) & SUN4C_SWP_OFF_MASK;
}

static swp_entry_t sun4c_swp_entry(unsigned long type, unsigned long offset)
{
	return (swp_entry_t) {
		  (offset & SUN4C_SWP_OFF_MASK) << SUN4C_SWP_OFF_SHIFT
		| (type & SUN4C_SWP_TYPE_MASK) };
}

static void sun4c_free_pte_slow(pte_t *pte)
{
	free_page((unsigned long)pte);
}

static void sun4c_free_pgd_slow(pgd_t *pgd)
{
	free_page((unsigned long)pgd);
}

static pgd_t *sun4c_get_pgd_fast(void)
{
	unsigned long *ret;

	if ((ret = pgd_quicklist) != NULL) {
		pgd_quicklist = (unsigned long *)(*ret);
		ret[0] = ret[1];
		pgtable_cache_size--;
	} else {
		pgd_t *init;
		
		ret = (unsigned long *)__get_free_page(GFP_KERNEL);
		memset (ret, 0, (KERNBASE / SUN4C_PGDIR_SIZE) * sizeof(pgd_t));
		init = sun4c_pgd_offset(&init_mm, 0);
		memcpy (((pgd_t *)ret) + USER_PTRS_PER_PGD, init + USER_PTRS_PER_PGD,
			(PTRS_PER_PGD - USER_PTRS_PER_PGD) * sizeof(pgd_t));
	}
	return (pgd_t *)ret;
}

static void sun4c_free_pgd_fast(pgd_t *pgd)
{
	*(unsigned long *)pgd = (unsigned long) pgd_quicklist;
	pgd_quicklist = (unsigned long *) pgd;
	pgtable_cache_size++;
}


static inline pte_t *
sun4c_pte_alloc_one_fast(struct mm_struct *mm, unsigned long address)
{
	unsigned long *ret;

	if ((ret = (unsigned long *)pte_quicklist) != NULL) {
		pte_quicklist = (unsigned long *)(*ret);
		ret[0] = ret[1];
		pgtable_cache_size--;
	}
	return (pte_t *)ret;
}

static pte_t *sun4c_pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
{
	pte_t *pte;

	if ((pte = sun4c_pte_alloc_one_fast(mm, address)) != NULL)
		return pte;

	pte = (pte_t *)get_zeroed_page(GFP_KERNEL|__GFP_REPEAT);
	return pte;
}

static pgtable_t sun4c_pte_alloc_one(struct mm_struct *mm, unsigned long address)
{
	pte_t *pte;
	struct page *page;

	pte = sun4c_pte_alloc_one_kernel(mm, address);
	if (pte == NULL)
		return NULL;
	page = virt_to_page(pte);
	pgtable_page_ctor(page);
	return page;
}

static inline void sun4c_free_pte_fast(pte_t *pte)
{
	*(unsigned long *)pte = (unsigned long) pte_quicklist;
	pte_quicklist = (unsigned long *) pte;
	pgtable_cache_size++;
}

static void sun4c_pte_free(pgtable_t pte)
{
	pgtable_page_dtor(pte);
	sun4c_free_pte_fast(page_address(pte));
}

/*
 * allocating and freeing a pmd is trivial: the 1-entry pmd is
 * inside the pgd, so has no extra memory…