NFC: digital: Add a delay between poll cycles

This replaces the polling work struct with a delayed work struct and add
a 10 ms delay between 2 poll cycles. This avoids to flood the device
with 'switch off'/'switch on' commands.
Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

include/net/nfc/digital.h

@@ -220,7 +220,7 @@ struct nfc_digital_dev {
 	struct list_head cmd_queue;
 	struct mutex cmd_lock;
 
-	struct work_struct poll_work;
+	struct delayed_work poll_work;
 
 	u8 curr_protocol;
 	u8 curr_rf_tech;

net/nfc/digital_core.c

@@ -30,6 +30,9 @@
 
 #define DIGITAL_PROTO_ISO15693_RF_TECH	NFC_PROTO_ISO15693_MASK
 
+/* Delay between each poll frame (ms) */
+#define DIGITAL_POLL_INTERVAL 10
+
 struct digital_cmd {
 	struct list_head queue;
 
@@ -419,7 +422,8 @@ void digital_poll_next_tech(struct nfc_digital_dev *ddev)
 
 	mutex_unlock(&ddev->poll_lock);
 
-	schedule_work(&ddev->poll_work);
+	schedule_delayed_work(&ddev->poll_work,
+			      msecs_to_jiffies(DIGITAL_POLL_INTERVAL));
 }
 
 static void digital_wq_poll(struct work_struct *work)
@@ -428,7 +432,7 @@ static void digital_wq_poll(struct work_struct *work)
 	struct digital_poll_tech *poll_tech;
 	struct nfc_digital_dev *ddev = container_of(work,
 						    struct nfc_digital_dev,
-						    poll_work);
+						    poll_work.work);
 	mutex_lock(&ddev->poll_lock);
 
 	if (!ddev->poll_tech_count) {
@@ -543,7 +547,7 @@ static int digital_start_poll(struct nfc_dev *nfc_dev, __u32 im_protocols,
 		return -EINVAL;
 	}
 
-	schedule_work(&ddev->poll_work);
+	schedule_delayed_work(&ddev->poll_work, 0);
 
 	return 0;
 }
@@ -564,7 +568,7 @@ static void digital_stop_poll(struct nfc_dev *nfc_dev)
 
 	mutex_unlock(&ddev->poll_lock);
 
-	cancel_work_sync(&ddev->poll_work);
+	cancel_delayed_work_sync(&ddev->poll_work);
 
 	digital_abort_cmd(ddev);
 }
@@ -770,7 +774,7 @@ struct nfc_digital_dev *nfc_digital_allocate_device(struct nfc_digital_ops *ops,
 	INIT_WORK(&ddev->cmd_complete_work, digital_wq_cmd_complete);
 
 	mutex_init(&ddev->poll_lock);
-	INIT_WORK(&ddev->poll_work, digital_wq_poll);
+	INIT_DELAYED_WORK(&ddev->poll_work, digital_wq_poll);
 
 	if (supported_protocols & NFC_PROTO_JEWEL_MASK)
 		ddev->protocols |= NFC_PROTO_JEWEL_MASK;
@@ -832,7 +836,7 @@ void nfc_digital_unregister_device(struct nfc_digital_dev *ddev)
 	ddev->poll_tech_count = 0;
 	mutex_unlock(&ddev->poll_lock);
 
-	cancel_work_sync(&ddev->poll_work);
+	cancel_delayed_work_sync(&ddev->poll_work);
 	cancel_work_sync(&ddev->cmd_work);
 	cancel_work_sync(&ddev->cmd_complete_work);