NFC: pn533: Fix the pn533 polling loop

By turning the radio off after each failed polling try, we dramatically
improve the pn533 polling loop efficiency.
Without this fix, all Android phones running the broadcom NFC stack are
almost never detected.
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/nfc/pn533.c

@@ -359,6 +359,7 @@ struct pn533 {
 	struct work_struct poll_work;
 	struct work_struct mi_work;
 	struct work_struct tg_work;
+	struct work_struct rf_work;
 
 	struct list_head cmd_queue;
 	struct pn533_cmd *cmd;
@@ -1660,6 +1661,53 @@ static void pn533_listen_mode_timer(unsigned long data)
 	queue_work(dev->wq, &dev->poll_work);
 }
 
+static int pn533_rf_complete(struct pn533 *dev, void *arg,
+			     struct sk_buff *resp)
+{
+	int rc = 0;
+
+	nfc_dev_dbg(&dev->interface->dev, "%s", __func__);
+
+	if (IS_ERR(resp)) {
+		rc = PTR_ERR(resp);
+
+		nfc_dev_err(&dev->interface->dev, "%s RF setting error %d",
+			    __func__, rc);
+
+		return rc;
+	}
+
+	queue_work(dev->wq, &dev->poll_work);
+
+	dev_kfree_skb(resp);
+	return rc;
+}
+
+static void pn533_wq_rf(struct work_struct *work)
+{
+	struct pn533 *dev = container_of(work, struct pn533, rf_work);
+	struct sk_buff *skb;
+	int rc;
+
+	nfc_dev_dbg(&dev->interface->dev, "%s", __func__);
+
+	skb = pn533_alloc_skb(dev, 2);
+	if (!skb)
+		return;
+
+	*skb_put(skb, 1) = PN533_CFGITEM_RF_FIELD;
+	*skb_put(skb, 1) = 0;
+
+	rc = pn533_send_cmd_async(dev, PN533_CMD_RF_CONFIGURATION, skb,
+				  pn533_rf_complete, NULL);
+	if (rc < 0) {
+		dev_kfree_skb(skb);
+		nfc_dev_err(&dev->interface->dev, "RF setting error %d", rc);
+	}
+
+	return;
+}
+
 static int pn533_poll_complete(struct pn533 *dev, void *arg,
 			       struct sk_buff *resp)
 {
@@ -1705,7 +1753,8 @@ static int pn533_poll_complete(struct pn533 *dev, void *arg,
 	}
 
 	pn533_poll_next_mod(dev);
-	queue_work(dev->wq, &dev->poll_work);
+	/* Not target found, turn radio off */
+	queue_work(dev->wq, &dev->rf_work);
 
 done:
 	dev_kfree_skb(resp);
@@ -2051,6 +2100,7 @@ static int pn533_mod_to_baud(struct pn533 *dev)
 	}
 }
 
+static int pn533_rf_field(struct nfc_dev *nfc_dev, u8 rf);
 #define PASSIVE_DATA_LEN 5
 static int pn533_dep_link_up(struct nfc_dev *nfc_dev, struct nfc_target *target,
 			     u8 comm_mode, u8 *gb, size_t gb_len)
@@ -2127,6 +2177,8 @@ static int pn533_dep_link_up(struct nfc_dev *nfc_dev, struct nfc_target *target,
 
 	*arg = !comm_mode;
 
+	pn533_rf_field(dev->nfc_dev, 0);
+
 	rc = pn533_send_cmd_async(dev, PN533_CMD_IN_JUMP_FOR_DEP, skb,
 				  pn533_in_dep_link_up_complete, arg);
 
@@ -2721,6 +2773,7 @@ static int pn533_probe(struct usb_interface *interface,
 	INIT_WORK(&dev->mi_work, pn533_wq_mi_recv);
 	INIT_WORK(&dev->tg_work, pn533_wq_tg_get_data);
 	INIT_WORK(&dev->poll_work, pn533_wq_poll);
+	INIT_WORK(&dev->rf_work, pn533_wq_rf);
 	dev->wq = alloc_ordered_workqueue("pn533", 0);
 	if (dev->wq == NULL)
 		goto error;