1 files changed, 29 insertions, 15 deletions

diff --git a/drivers/s390/cio/cmf.c b/drivers/s390/cio/cmf.c
index b2afad5a5682..268aa23afa01 100644
--- a/drivers/s390/cio/cmf.c
+++ b/drivers/s390/cio/cmf.c
@@ -164,6 +164,9 @@ static inline u64 time_to_avg_nsec(u32 value, u32 count)
 	return ret;
 }
 
+#define CMF_OFF 0
+#define CMF_ON	2
+
 /*
  * Activate or deactivate the channel monitor. When area is NULL,
  * the monitor is deactivated. The channel monitor needs to
@@ -176,7 +179,7 @@ static inline void cmf_activate(void *area, unsigned int onoff)
 	register long __gpr1 asm("1");
 
 	__gpr2 = area;
-	__gpr1 = onoff ? 2 : 0;
+	__gpr1 = onoff;
 	/* activate channel measurement */
 	asm("schm" : : "d" (__gpr2), "d" (__gpr1) );
 }
@@ -587,7 +590,7 @@ static int alloc_cmb(struct ccw_device *cdev)
 			/* everything ok */
 			memset(mem, 0, size);
 			cmb_area.mem = mem;
-			cmf_activate(cmb_area.mem, 1);
+			cmf_activate(cmb_area.mem, CMF_ON);
 		}
 	}
 
@@ -621,7 +624,7 @@ static void free_cmb(struct ccw_device *cdev)
 	if (list_empty(&cmb_area.list)) {
 		ssize_t size;
 		size = sizeof(struct cmb) * cmb_area.num_channels;
-		cmf_activate(NULL, 0);
+		cmf_activate(NULL, CMF_OFF);
 		free_pages((unsigned long)cmb_area.mem, get_order(size));
 		cmb_area.mem = NULL;
 	}
@@ -753,6 +756,17 @@ static void reset_cmb(struct ccw_device *cdev)
 	cmf_generic_reset(cdev);
 }
 
+static int cmf_enabled(struct ccw_device *cdev)
+{
+	int enabled;
+
+	spin_lock_irq(cdev->ccwlock);
+	enabled = !!cdev->private->cmb;
+	spin_unlock_irq(cdev->ccwlock);
+
+	return enabled;
+}
+
 static struct attribute_group cmf_attr_group;
 
 static struct cmb_operations cmbops_basic = {
@@ -830,7 +844,7 @@ static int alloc_cmbe(struct ccw_device *cdev)
 
 	/* activate global measurement if this is the first channel */
 	if (list_empty(&cmb_area.list))
-		cmf_activate(NULL, 1);
+		cmf_activate(NULL, CMF_ON);
 	list_add_tail(&cdev->private->cmb_list, &cmb_area.list);
 
 	spin_unlock_irq(cdev->ccwlock);
@@ -867,7 +881,7 @@ static void free_cmbe(struct ccw_device *cdev)
 	/* deactivate global measurement if this is the last channel */
 	list_del_init(&cdev->private->cmb_list);
 	if (list_empty(&cmb_area.list))
-		cmf_activate(NULL, 0);
+		cmf_activate(NULL, CMF_OFF);
 	spin_unlock_irq(cdev->ccwlock);
 	spin_unlock(&cmb_area.lock);
 }
@@ -1153,13 +1167,8 @@ static ssize_t cmb_enable_show(struct device *dev,
 			       char *buf)
 {
 	struct ccw_device *cdev = to_ccwdev(dev);
-	int enabled;
 
-	spin_lock_irq(cdev->ccwlock);
-	enabled = !!cdev->private->cmb;
-	spin_unlock_irq(cdev->ccwlock);
-
-	return sprintf(buf, "%d\n", enabled);
+	return sprintf(buf, "%d\n", cmf_enabled(cdev));
 }
 
 static ssize_t cmb_enable_store(struct device *dev,
@@ -1199,15 +1208,20 @@ int ccw_set_cmf(struct ccw_device *cdev, int enable)
  *  @cdev:	The ccw device to be enabled
  *
  *  Returns %0 for success or a negative error value.
- *
+ *  Note: If this is called on a device for which channel measurement is already
+ *	  enabled a reset of the measurement data is triggered.
  *  Context:
  *    non-atomic
  */
 int enable_cmf(struct ccw_device *cdev)
 {
-	int ret;
+	int ret = 0;
 
 	device_lock(&cdev->dev);
+	if (cmf_enabled(cdev)) {
+		cmbops->reset(cdev);
+		goto out_unlock;
+	}
 	get_device(&cdev->dev);
 	ret = cmbops->alloc(cdev);
 	if (ret)
@@ -1226,7 +1240,7 @@ int enable_cmf(struct ccw_device *cdev)
 out:
 	if (ret)
 		put_device(&cdev->dev);
-
+out_unlock:
 	device_unlock(&cdev->dev);
 	return ret;
 }
@@ -1321,7 +1335,7 @@ void cmf_reactivate(void)
 {
 	spin_lock(&cmb_area.lock);
 	if (!list_empty(&cmb_area.list))
-		cmf_activate(cmb_area.mem, 1);
+		cmf_activate(cmb_area.mem, CMF_ON);
 	spin_unlock(&cmb_area.lock);
 }