Input: ads7846 - handle IRQs that were latched during disabled IRQs

The pen down IRQ will toggle during each X,Y,Z measurement cycle.
Even though the IRQ is disabled it will be latched and delivered
when after enable_irq. Thus in the IRQ handler we must avoid
starting a new measurement cycle when such an "unwanted" IRQ happens.
Add a get_pendown_state platform function, which will probably
determine this by reading the current GPIO level of the pen IRQ pin.

Move the IRQ reenabling from the SPI RX function to the timer. After
the last power down message the pen IRQ pin is still active for a
while and get_pendown_state would report incorrectly a pen down state.

When suspending we should check the ts->pending flag instead of
ts->pendown, since the timer can be pending regardless of ts->pendown.
Also if ts->pending is set we can be sure that the timer is running,
so no need to rearm it. Similarly if ts->pending is not set we can
be sure that the IRQ is enabled (and the timer is not).

Signed-off-by: Imre Deak <imre.deak@nokia.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/touchscreen/ads7846.c

@@ -102,6 +102,8 @@ struct ads7846 {
 // FIXME remove "irq_disabled"
 	unsigned		irq_disabled:1;	/* P: lock */
 	unsigned		disabled:1;
+
+	int			(*get_pendown_state)(void);
 };
 
 /* leave chip selected when we're done, for quicker re-select? */
@@ -175,6 +177,12 @@ struct ser_req {
 static void ads7846_enable(struct ads7846 *ts);
 static void ads7846_disable(struct ads7846 *ts);
 
+static int device_suspended(struct device *dev)
+{
+	struct ads7846 *ts = dev_get_drvdata(dev);
+	return dev->power.power_state.event != PM_EVENT_ON || ts->disabled;
+}
+
 static int ads7846_read12_ser(struct device *dev, unsigned command)
 {
 	struct spi_device	*spi = to_spi_device(dev);
@@ -227,8 +235,10 @@ static int ads7846_read12_ser(struct device *dev, unsigned command)
 	for (i = 0; i < 6; i++)
 		spi_message_add_tail(&req->xfer[i], &req->msg);
 
+	ts->irq_disabled = 1;
 	disable_irq(spi->irq);
 	status = spi_sync(spi, &req->msg);
+	ts->irq_disabled = 0;
 	enable_irq(spi->irq);
 
 	if (req->msg.status)
@@ -333,7 +343,7 @@ static void ads7846_rx(void *ads)
 	if (x == MAX_12BIT)
 		x = 0;
 
-	if (x && z1 && ts->spi->dev.power.power_state.event == PM_EVENT_ON) {
+	if (likely(x && z1 && !device_suspended(&ts->spi->dev))) {
 		/* compute touch pressure resistance using equation #2 */
 		Rt = z2;
 		Rt -= z1;
@@ -377,20 +387,10 @@ static void ads7846_rx(void *ads)
 			x, y, Rt, Rt ? "" : " UP");
 #endif
 
-	/* don't retrigger while we're suspended */
 	spin_lock_irqsave(&ts->lock, flags);
 
 	ts->pendown = (Rt != 0);
-	ts->pending = 0;
-
-	if (ts->spi->dev.power.power_state.event == PM_EVENT_ON) {
-		if (ts->pendown)
-			mod_timer(&ts->timer, jiffies + TS_POLL_PERIOD);
-		else if (ts->irq_disabled) {
-			ts->irq_disabled = 0;
-			enable_irq(ts->spi->irq);
-		}
-	}
+	mod_timer(&ts->timer, jiffies + TS_POLL_PERIOD);
 
 	spin_unlock_irqrestore(&ts->lock, flags);
 }
@@ -431,10 +431,25 @@ static void ads7846_timer(unsigned long handle)
 	struct ads7846	*ts = (void *)handle;
 	int		status = 0;
 
-	ts->msg_idx = 0;
-	status = spi_async(ts->spi, &ts->msg[0]);
-	if (status)
-		dev_err(&ts->spi->dev, "spi_async --> %d\n", status);
+	spin_lock_irq(&ts->lock);
+
+	if (unlikely(ts->msg_idx && !ts->pendown)) {
+		/* measurment cycle ended */
+		if (!device_suspended(&ts->spi->dev)) {
+			ts->irq_disabled = 0;
+			enable_irq(ts->spi->irq);
+		}
+		ts->pending = 0;
+		ts->msg_idx = 0;
+	} else {
+		/* pen is still down, continue with the measurement */
+		ts->msg_idx = 0;
+		status = spi_async(ts->spi, &ts->msg[0]);
+		if (status)
+			dev_err(&ts->spi->dev, "spi_async --> %d\n", status);
+	}
+
+	spin_unlock_irq(&ts->lock);
 }
 
 static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)
@@ -443,7 +458,7 @@ static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)
 	unsigned long flags;
 
 	spin_lock_irqsave(&ts->lock, flags);
-	if (likely(!ts->irq_disabled && !ts->disabled)) {
+	if (likely(ts->get_pendown_state())) {
 		if (!ts->irq_disabled) {
 			/* REVISIT irq logic for many ARM chips has cloned a
 			 * bug wherein disabling an irq in its handler won't
@@ -452,10 +467,7 @@ static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)
 			 * that state here.
 			 */
 			ts->irq_disabled = 1;
-
 			disable_irq(ts->spi->irq);
-		}
-		if (!ts->pending) {
 			ts->pending = 1;
 			mod_timer(&ts->timer, jiffies);
 		}
@@ -473,20 +485,17 @@ static void ads7846_disable(struct ads7846 *ts)
 	if (ts->disabled)
 		return;
 
+	ts->disabled = 1;
+
 	/* are we waiting for IRQ, or polling? */
-	if (!ts->pendown) {
-		if (!ts->irq_disabled) {
-			ts->irq_disabled = 1;
-			disable_irq(ts->spi->irq);
-		}
+	if (!ts->pending) {
+		ts->irq_disabled = 1;
+		disable_irq(ts->spi->irq);
 	} else {
-		/* polling; force a final SPI completion;
-		 * that will clean things up neatly
+		/* the timer will run at least once more, and
+		 * leave everything in a clean state, IRQ disabled
 		 */
-		if (!ts->pending)
-			mod_timer(&ts->timer, jiffies);
-
-		while (ts->pendown || ts->pending) {
+		while (ts->pending) {
 			spin_unlock_irq(&ts->lock);
 			msleep(1);
 			spin_lock_irq(&ts->lock);
@@ -497,7 +506,6 @@ static void ads7846_disable(struct ads7846 *ts)
 	 * leave it that way after every request
 	 */
 
-	ts->disabled = 1;
 }
 
 /* Must be called with ts->lock held */
@@ -566,6 +574,11 @@ static int __devinit ads7846_probe(struct spi_device *spi)
 		return -EINVAL;
 	}
 
+	if (pdata->get_pendown_state == NULL) {
+		dev_dbg(&spi->dev, "no get_pendown_state function?\n");
+		return -EINVAL;
+	}
+
 	/* We'd set the wordsize to 12 bits ... except that some controllers
 	 * will then treat the 8 bit command words as 12 bits (and drop the
 	 * four MSBs of the 12 bit result).  Result: inputs must be shifted
@@ -596,6 +609,7 @@ static int __devinit ads7846_probe(struct spi_device *spi)
 	ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
 	ts->debounce_max = pdata->debounce_max ? : 1;
 	ts->debounce_tol = pdata->debounce_tol ? : 10;
+	ts->get_pendown_state = pdata->get_pendown_state;
 
 	snprintf(ts->phys, sizeof(ts->phys), "%s/input0", spi->dev.bus_id);
 
@@ -786,8 +800,8 @@ static int __devexit ads7846_remove(struct spi_device *spi)
 	device_remove_file(&spi->dev, &dev_attr_vaux);
 
 	free_irq(ts->spi->irq, ts);
-	if (ts->irq_disabled)
-		enable_irq(ts->spi->irq);
+	/* suspend left the IRQ disabled */
+	enable_irq(ts->spi->irq);
 
 	kfree(ts);
 

include/linux/spi/ads7846.h

@@ -17,5 +17,7 @@ struct ads7846_platform_data {
 
 	u16	debounce_max;		/* max number of readings per sample */
 	u16	debounce_tol;		/* tolerance used for filtering */
+
+	int	(*get_pendown_state)(void);
 };