diff --git a/drivers/ide/pci/cmd640.c b/drivers/ide/pci/cmd640.c
index f369645..0e9275d 100644
--- a/drivers/ide/pci/cmd640.c
+++ b/drivers/ide/pci/cmd640.c
@@ -185,6 +185,8 @@
 
 #endif /* CONFIG_BLK_DEV_CMD640_ENHANCED */
 
+static DEFINE_SPINLOCK(cmd640_lock);
+
 /*
  * These are initialized to point at the devices we control
  */
@@ -258,12 +260,12 @@
 
 static u8 get_cmd640_reg(u16 reg)
 {
-	u8 b;
 	unsigned long flags;
+	u8 b;
 
-	spin_lock_irqsave(&ide_lock, flags);
+	spin_lock_irqsave(&cmd640_lock, flags);
 	b = __get_cmd640_reg(reg);
-	spin_unlock_irqrestore(&ide_lock, flags);
+	spin_unlock_irqrestore(&cmd640_lock, flags);
 	return b;
 }
 
@@ -271,9 +273,9 @@
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&ide_lock, flags);
+	spin_lock_irqsave(&cmd640_lock, flags);
 	__put_cmd640_reg(reg,val);
-	spin_unlock_irqrestore(&ide_lock, flags);
+	spin_unlock_irqrestore(&cmd640_lock, flags);
 }
 
 static int __init match_pci_cmd640_device (void)
@@ -351,7 +353,7 @@
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&ide_lock, flags);
+	spin_lock_irqsave(&cmd640_lock, flags);
 
 	outb_p(0x0a, 0x170 + IDE_SELECT_OFFSET);	/* select drive0 */
 	udelay(100);
@@ -359,11 +361,11 @@
 		outb_p(0x1a, 0x170 + IDE_SELECT_OFFSET); /* select drive1 */
 		udelay(100);
 		if ((inb_p(0x170 + IDE_SELECT_OFFSET) & 0x1f) != 0x1a) {
-			spin_unlock_irqrestore(&ide_lock, flags);
+			spin_unlock_irqrestore(&cmd640_lock, flags);
 			return 0; /* nothing responded */
 		}
 	}
-	spin_unlock_irqrestore(&ide_lock, flags);
+	spin_unlock_irqrestore(&cmd640_lock, flags);
 	return 1; /* success */
 }
 
@@ -440,11 +442,11 @@
 static void set_prefetch_mode (unsigned int index, int mode)
 {
 	ide_drive_t *drive = cmd_drives[index];
+	unsigned long flags;
 	int reg = prefetch_regs[index];
 	u8 b;
-	unsigned long flags;
 
-	spin_lock_irqsave(&ide_lock, flags);
+	spin_lock_irqsave(&cmd640_lock, flags);
 	b = __get_cmd640_reg(reg);
 	if (mode) {	/* want prefetch on? */
 #if CMD640_PREFETCH_MASKS
@@ -460,7 +462,7 @@
 		b |= prefetch_masks[index];	/* disable prefetch */
 	}
 	__put_cmd640_reg(reg, b);
-	spin_unlock_irqrestore(&ide_lock, flags);
+	spin_unlock_irqrestore(&cmd640_lock, flags);
 }
 
 /*
@@ -561,7 +563,7 @@
 	/*
 	 * Now that everything is ready, program the new timings
 	 */
-	spin_lock_irqsave(&ide_lock, flags);
+	spin_lock_irqsave(&cmd640_lock, flags);
 	/*
 	 * Program the address_setup clocks into ARTTIM reg,
 	 * and then the active/recovery counts into the DRWTIM reg
@@ -570,7 +572,7 @@
 	setup_count |= __get_cmd640_reg(arttim_regs[index]) & 0x3f;
 	__put_cmd640_reg(arttim_regs[index], setup_count);
 	__put_cmd640_reg(drwtim_regs[index], pack_nibbles(active_count, recovery_count));
-	spin_unlock_irqrestore(&ide_lock, flags);
+	spin_unlock_irqrestore(&cmd640_lock, flags);
 }
 
 /*
@@ -630,6 +632,7 @@
 
 static void cmd640_set_pio_mode(ide_drive_t *drive, const u8 pio)
 {
+	unsigned long flags;
 	unsigned int index = 0, cycle_time;
 	u8 b;
 
@@ -652,7 +655,12 @@
 
 		case 8: /* set prefetch off */
 		case 9: /* set prefetch on */
+			/*
+			 * take ide_lock for drive->[no_]unmask/[no_]io_32bit
+			 */
+			spin_lock_irqsave(&ide_lock, flags);
 			set_prefetch_mode(index, pio & 1);
+			spin_unlock_irqrestore(&ide_lock, flags);
 			printk("%s: %sabled cmd640 prefetch\n", drive->name, (pio & 1) ? "en" : "dis");
 			return;
 	}
@@ -670,20 +678,20 @@
 
 static int pci_conf1(void)
 {
-	u32 tmp;
 	unsigned long flags;
+	u32 tmp;
 
-	spin_lock_irqsave(&ide_lock, flags);
+	spin_lock_irqsave(&cmd640_lock, flags);
 	outb(0x01, 0xCFB);
 	tmp = inl(0xCF8);
 	outl(0x80000000, 0xCF8);
 	if (inl(0xCF8) == 0x80000000) {
 		outl(tmp, 0xCF8);
-		spin_unlock_irqrestore(&ide_lock, flags);
+		spin_unlock_irqrestore(&cmd640_lock, flags);
 		return 1;
 	}
 	outl(tmp, 0xCF8);
-	spin_unlock_irqrestore(&ide_lock, flags);
+	spin_unlock_irqrestore(&cmd640_lock, flags);
 	return 0;
 }
 
@@ -691,15 +699,15 @@
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&ide_lock, flags);
+	spin_lock_irqsave(&cmd640_lock, flags);
 	outb(0x00, 0xCFB);
 	outb(0x00, 0xCF8);
 	outb(0x00, 0xCFA);
 	if (inb(0xCF8) == 0x00 && inb(0xCF8) == 0x00) {
-		spin_unlock_irqrestore(&ide_lock, flags);
+		spin_unlock_irqrestore(&cmd640_lock, flags);
 		return 1;
 	}
-	spin_unlock_irqrestore(&ide_lock, flags);
+	spin_unlock_irqrestore(&cmd640_lock, flags);
 	return 0;
 }