ht6560b: fix deadlock on error handling

Stop abusing ide_lock lock (switch to a private locking).

Fixes same issue as fixed by Alan Cox in atiixp host driver with
commit 6c5f8cc3.

ht6560b is a bit special cause we still need to leave ide_lock for
->set_pio_mode with 'pio' argument == 8/9 (prefetch disable/enable).
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/legacy/ht6560b.c

@@ -247,6 +247,8 @@ static u8 ht_pio2timings(ide_drive_t *drive, const u8 pio)
 	}
 }
 
+static DEFINE_SPINLOCK(ht6560b_lock);
+
 /*
  *  Enable/Disable so called prefetch mode
  */
@@ -255,7 +257,7 @@ static void ht_set_prefetch(ide_drive_t *drive, u8 state)
 	unsigned long flags;
 	int t = HT_PREFETCH_MODE << 8;
 
-	spin_lock_irqsave(&ide_lock, flags);
+	spin_lock_irqsave(&ht6560b_lock, flags);
 
 	/*
 	 *  Prefetch mode and unmask irq seems to conflict
@@ -269,7 +271,7 @@ static void ht_set_prefetch(ide_drive_t *drive, u8 state)
 		drive->no_unmask = 0;
 	}
 
-	spin_unlock_irqrestore(&ide_lock, flags);
+	spin_unlock_irqrestore(&ht6560b_lock, flags);
 
 #ifdef DEBUG
 	printk("ht6560b: drive %s prefetch mode %sabled\n", drive->name, (state ? "en" : "dis"));
@@ -284,18 +286,21 @@ static void ht6560b_set_pio_mode(ide_drive_t *drive, const u8 pio)
 	switch (pio) {
 	case 8:         /* set prefetch off */
 	case 9:         /* set prefetch on */
+		/*
+		 * take ide_lock for drive->[no_]unmask
+		 */
+		spin_lock_irqsave(&ide_lock, flags);
 		ht_set_prefetch(drive, pio & 1);
+		spin_unlock_irqrestore(&ide_lock, flags);
 		return;
 	}
 
 	timing = ht_pio2timings(drive, pio);
 
-	spin_lock_irqsave(&ide_lock, flags);
-	
+	spin_lock_irqsave(&ht6560b_lock, flags);
 	drive->drive_data &= 0xff00;
 	drive->drive_data |= timing;
-	
-	spin_unlock_irqrestore(&ide_lock, flags);
+	spin_unlock_irqrestore(&ht6560b_lock, flags);
 
 #ifdef DEBUG
 	printk("ht6560b: drive %s tuned to pio mode %#x timing=%#x\n", drive->name, pio, timing);