[media] mb86a20s: fix the PER reset logic

The logic that resets the device is wrong. It should be resetting
just the layer that got read. Also, stop is needed before updating
the counters.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/dvb-frontends/mb86a20s.c

@@ -934,7 +934,7 @@ static int mb86a20s_get_blk_error(struct dvb_frontend *fe,
 			    u32 *error, u32 *count)
 {
 	struct mb86a20s_state *state = fe->demodulator_priv;
-	int rc;
+	int rc, val;
 	u32 collect_rate;
 	dev_dbg(&state->i2c->dev, "%s called.\n", __func__);
 
@@ -1007,7 +1007,6 @@ static int mb86a20s_get_blk_error(struct dvb_frontend *fe,
 		goto reset_measurement;
 
 	collect_rate = state->estimated_rate[layer] / 204 / 8;
-
 	if (collect_rate < 32)
 		collect_rate = 32;
 	if (collect_rate > 65535)
@@ -1017,6 +1016,16 @@ static int mb86a20s_get_blk_error(struct dvb_frontend *fe,
 		dev_dbg(&state->i2c->dev,
 			"%s: updating PER counter on layer %c to %d.\n",
 			__func__, 'A' + layer, collect_rate);
+
+		/* Stop PER measurement */
+		rc = mb86a20s_writereg(state, 0x50, 0xb0);
+		if (rc < 0)
+			return rc;
+		rc = mb86a20s_writereg(state, 0x51, 0x00);
+		if (rc < 0)
+			return rc;
+
+		/* Update this layer's counter */
 		rc = mb86a20s_writereg(state, 0x50, 0xb2 + layer * 2);
 		if (rc < 0)
 			return rc;
@@ -1029,6 +1038,25 @@ static int mb86a20s_get_blk_error(struct dvb_frontend *fe,
 		rc = mb86a20s_writereg(state, 0x51, collect_rate & 0xff);
 		if (rc < 0)
 			return rc;
+
+		/* start PER measurement */
+		rc = mb86a20s_writereg(state, 0x50, 0xb0);
+		if (rc < 0)
+			return rc;
+		rc = mb86a20s_writereg(state, 0x51, 0x07);
+		if (rc < 0)
+			return rc;
+
+		/* Reset all counters to collect new data */
+		rc = mb86a20s_writereg(state, 0x50, 0xb1);
+		if (rc < 0)
+			return rc;
+		rc = mb86a20s_writereg(state, 0x51, 0x07);
+		if (rc < 0)
+			return rc;
+		rc = mb86a20s_writereg(state, 0x51, 0x00);
+
+		return rc;
 	}
 
 reset_measurement:
@@ -1036,14 +1064,16 @@ static int mb86a20s_get_blk_error(struct dvb_frontend *fe,
 	rc = mb86a20s_writereg(state, 0x50, 0xb1);
 	if (rc < 0)
 		return rc;
-	rc = mb86a20s_writereg(state, 0x51, (1 << layer));
+	rc = mb86a20s_readreg(state, 0x51);
 	if (rc < 0)
 		return rc;
-	rc = mb86a20s_writereg(state, 0x51, 0x00);
+	val = rc;
+	rc = mb86a20s_writereg(state, 0x51, val | (1 << layer));
 	if (rc < 0)
 		return rc;
+	rc = mb86a20s_writereg(state, 0x51, val & ~(1 << layer));
 
-	return 0;
+	return rc;
 }
 
 struct linear_segments {