===== arch/ppc/mm/pgtable.c 1.19 vs edited =====
--- 1.19/arch/ppc/mm/pgtable.c	Sat May 22 14:56:23 2004
+++ edited/arch/ppc/mm/pgtable.c	Fri Jun  4 16:28:44 2004
@@ -10,6 +10,8 @@
  *    Copyright (C) 1996 Paul Mackerras
  *  Amiga/APUS changes by Jesper Skov (jskov@cygnus.co.uk).
  *
+ *  Simple ioremap cache added by Eugene Surovegin <ebs@ebshome.net>, 2004
+ *
  *  Derived from "arch/i386/mm/init.c"
  *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
  *
@@ -59,6 +61,17 @@
 #define p_mapped_by_bats(x)	(0UL)
 #endif /* HAVE_BATS */
 
+/* simple ioremap cache */
+#define IOREMAP_CACHE_SIZE	10
+static spinlock_t ioremap_cache_lock = SPIN_LOCK_UNLOCKED;
+static int ioremap_cache_active_slots;
+static struct ioremap_cache_entry {
+	phys_addr_t 		pa;
+	unsigned long		va;
+	unsigned long		flags;
+	int			users;
+} ioremap_cache[IOREMAP_CACHE_SIZE];
+
 #ifdef CONFIG_44x
 /* 44x uses an 8kB pgdir because it has 8-byte Linux PTEs. */
 #define PGDIR_ORDER	1
@@ -137,6 +150,84 @@
 	__free_page(ptepage);
 }
 
+static unsigned long ioremap_cache_check(phys_addr_t pa, unsigned long size, 
+					    unsigned long flags)
+{
+	unsigned long va = 0;
+	int i;
+
+	if (size != 0x1000)
+		return 0;
+
+	spin_lock(&ioremap_cache_lock);
+	if (!ioremap_cache_active_slots)
+		goto out;
+	
+	for (i = 0; i < IOREMAP_CACHE_SIZE; ++i)
+		if (ioremap_cache[i].pa == pa && 
+		    ioremap_cache[i].flags == flags)
+		{
+			va = ioremap_cache[i].va;
+			++ioremap_cache[i].users;
+			break;
+		}
+out:
+	spin_unlock(&ioremap_cache_lock);
+
+	return va;
+}
+
+static void ioremap_cache_add(phys_addr_t pa, unsigned long va, unsigned long size, 
+				unsigned long flags)
+{
+	int i;
+
+	if (size != 0x1000)
+		return;
+
+	spin_lock(&ioremap_cache_lock);
+	if (ioremap_cache_active_slots == IOREMAP_CACHE_SIZE)
+		goto out;
+	
+	for (i = 0; i < IOREMAP_CACHE_SIZE; ++i)
+		if (!ioremap_cache[i].pa){
+			ioremap_cache[i].pa = pa;
+			ioremap_cache[i].va = va;
+			ioremap_cache[i].flags = flags;
+			ioremap_cache[i].users = 1;
+			++ioremap_cache_active_slots;
+			break;
+		}
+out:
+	spin_unlock(&ioremap_cache_lock);
+}
+
+static int ioremap_cache_del(unsigned long va)
+{
+	int i, res = 0;
+	va &= PAGE_MASK;
+
+	spin_lock(&ioremap_cache_lock);
+	if (!ioremap_cache_active_slots)
+		goto out;
+	
+	for (i = 0; i < IOREMAP_CACHE_SIZE; ++i)
+		if (ioremap_cache[i].va == va){
+			res = --ioremap_cache[i].users;
+			if (!res){
+				ioremap_cache[i].pa = 0;
+				ioremap_cache[i].va = 0;
+				ioremap_cache[i].flags = 0;
+				--ioremap_cache_active_slots;
+			}
+			break;
+		}
+out:
+	spin_unlock(&ioremap_cache_lock);
+    
+	return res;
+}
+
 #ifndef CONFIG_44x
 void *
 ioremap(phys_addr_t addr, unsigned long size)
@@ -210,6 +301,14 @@
 	if ((v = p_mapped_by_bats(p)) /*&& p_mapped_by_bats(p+size-1)*/ )
 		goto out;
 
+	if ((flags & _PAGE_PRESENT) == 0)
+		flags |= _PAGE_KERNEL;
+	if (flags & _PAGE_NO_CACHE)
+		flags |= _PAGE_GUARDED;
+
+	if ((v = ioremap_cache_check(p, size, flags)))
+		goto out;
+
 	if (mem_init_done) {
 		struct vm_struct *area;
 		area = get_vm_area(size, VM_IOREMAP);
@@ -220,11 +319,6 @@
 		v = (ioremap_bot -= size);
 	}
 
-	if ((flags & _PAGE_PRESENT) == 0)
-		flags |= _PAGE_KERNEL;
-	if (flags & _PAGE_NO_CACHE)
-		flags |= _PAGE_GUARDED;
-
 	/*
 	 * Should check if it is a candidate for a BAT mapping
 	 */
@@ -238,6 +332,7 @@
 		return NULL;
 	}
 
+	ioremap_cache_add(p, v, size, flags);
 out:
 	return (void *) (v + ((unsigned long)addr & ~PAGE_MASK));
 }
@@ -250,8 +345,9 @@
 	 */
 	if (v_mapped_by_bats((unsigned long)addr)) return;
 
-	if (addr > high_memory && (unsigned long) addr < ioremap_bot)
-		vunmap((void *) (PAGE_MASK & (unsigned long)addr));
+	if (!ioremap_cache_del((unsigned long)addr))
+		if (addr > high_memory && (unsigned long) addr < ioremap_bot)
+			vunmap((void *) (PAGE_MASK & (unsigned long)addr));
 }
 
 int