input: atmel_ptc: add tracking support

The PTC sends too many IRQs, it causes to miss some of them. Most of the
time, it's not an issue since it concerns position reporting.
Unfortunately, we can miss IRQ about touch event. In this case, we can't
report that the scroller is no longer touched.

To avoid this situation, use a tasklet to perform a kind of tracking.
While tracking the position, IRQs received are discarded. To perform the
tracking, a tasklet is used to monitor the scroller position and status
until the status is set to "not touch".

Signed-off-by: Ludovic Desroches <ludovic.desroches@microchip.com>

Author: ldesroches

drivers/input/misc/atmel_ptc.c

@@ -186,12 +186,14 @@ struct atmel_ptc {
 	int				irq;
 	u8				imr;
 	struct completion		ppp_ack;
+	struct tasklet_struct		tasklet;
 	unsigned int			button_keycode[ATMEL_PTC_MAX_NODES];
 	bool				buttons_registered;
 	bool				scroller_registered[ATMEL_PTC_MAX_SCROLLERS];
 	u32				button_event[ATMEL_PTC_MAX_NODES / 32];
 	u32				button_state[ATMEL_PTC_MAX_NODES / 32];
 	u32				scroller_event;
+	bool				scroller_tracking;
 	char				fw_version[ATMEL_PPP_FW_FOOTER_SIZE];
 };
 
@@ -403,29 +405,29 @@ static u32 atmel_qtm_get_touch_events_scroller_event_id(struct atmel_ptc *ptc)
 
 static void atmel_ptc_irq_scroller_event(struct atmel_ptc *ptc)
 {
-	unsigned long i;
+	unsigned int status, i;
 
-	if (!ptc->scroller_event)
+	if (!ptc->scroller_event || ptc->scroller_tracking)
 		return;
 
-	for_each_set_bit(i, (unsigned long *)&ptc->scroller_event, ATMEL_PTC_MAX_SCROLLERS) {
-		unsigned int scroller_type =
-			atmel_qtm_get_scroller_type(ptc, i);
-		unsigned int position =
-			atmel_qtm_get_scroller_position(ptc, i);
-		unsigned int status =
-			atmel_qtm_get_scroller_status(ptc, i);
-
-		if (scroller_type == ATMEL_QTM_SCROLLER_TYPE_WHEEL)
-			input_report_abs(ptc->scroller_input[i],
-					 ABS_WHEEL, position);
-		else
-			input_report_abs(ptc->scroller_input[i],
-					 ABS_X, position);
+	/*
+	 * Report the touch event and let the tasklet tracking the position
+	 * until the scrollers are no longer touched.
+	 */
+	for (i = 0 ; i < ATMEL_PTC_MAX_SCROLLERS; i++) {
+		if (!ptc->scroller_input[i])
+			break;
+
+		status = atmel_qtm_get_scroller_status(ptc, i);
 
 		input_report_key(ptc->scroller_input[i], BTN_TOUCH,
 				 status & 0x1);
 		input_sync(ptc->scroller_input[i]);
+
+		if (status & 0x1) {
+			ptc->scroller_tracking = true;
+			tasklet_schedule(&ptc->tasklet);
+		}
 	}
 }
 
@@ -724,6 +726,37 @@ static int atmel_ptc_cmd_send(struct atmel_ptc *ptc, struct atmel_qtm_cmd *cmd)
 	return 0;
 }
 
+static void atmel_ptc_tasklet(unsigned long priv)
+{
+	struct atmel_ptc *ptc = (struct atmel_ptc *)priv;
+	unsigned int scroller_type, position, status, i;
+
+	for (i = 0 ; i < ATMEL_PTC_MAX_SCROLLERS; i++) {
+		if (!ptc->scroller_input[i])
+			break;
+
+		scroller_type = atmel_qtm_get_scroller_type(ptc, i);
+		position = atmel_qtm_get_scroller_position(ptc, i);
+		status = atmel_qtm_get_scroller_status(ptc, i);
+
+		if (status & 0x1) {
+			if (scroller_type == ATMEL_QTM_SCROLLER_TYPE_WHEEL)
+				input_report_abs(ptc->scroller_input[i],
+						 ABS_WHEEL, position);
+			else
+				input_report_abs(ptc->scroller_input[i],
+						 ABS_X, position);
+			input_sync(ptc->scroller_input[i]);
+			tasklet_schedule(&ptc->tasklet);
+		} else {
+			input_report_key(ptc->scroller_input[i], BTN_TOUCH, 0);
+			input_sync(ptc->scroller_input[i]);
+
+			ptc->scroller_tracking = false;
+		}
+	}
+}
+
 static int atmel_ptc_conf_load(struct atmel_ptc *ptc)
 {
 	const struct firmware *conf;
@@ -1024,13 +1057,16 @@ static int atmel_ptc_probe(struct platform_device *pdev)
 	if (debug_mode)
 		ret = sysfs_create_group(&ptc->dev->kobj, &atmel_ptc_qtm_mb_attr_group);
 
+	tasklet_init(&ptc->tasklet, atmel_ptc_tasklet, (unsigned long)ptc);
+
 	return ret;
 }
 
 static int atmel_ptc_remove(struct platform_device *pdev)
 {
 	struct atmel_ptc *ptc = platform_get_drvdata(pdev);
 
+	tasklet_kill(&ptc->tasklet);
 	atmel_ptc_unregister_input_devices(ptc);
 	atmel_ptc_free_pins(ptc);