staging:iio:trigger:bfintmr: Only enable timer when necessary

This patch hooks up the set_trigger_state callback for the blackfin timer
trigger driver and only enables the timer when a trigger consumer requests it to
be enabled. There really is no reason to keep the timer running and generate
interrupts if nobody is listening to them.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/trigger/iio-trig-bfin-timer.c

@@ -57,12 +57,28 @@ struct bfin_tmr_state {
 	int irq;
 };
 
+static int iio_bfin_tmr_set_state(struct iio_trigger *trig, bool state)
+{
+	struct bfin_tmr_state *st = trig->private_data;
+
+	if (get_gptimer_period(st->t->id) == 0)
+		return -EINVAL;
+
+	if (state)
+		enable_gptimers(st->t->bit);
+	else
+		disable_gptimers(st->t->bit);
+
+	return 0;
+}
+
 static ssize_t iio_bfin_tmr_frequency_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t count)
 {
 	struct iio_trigger *trig = to_iio_trigger(dev);
 	struct bfin_tmr_state *st = trig->private_data;
 	long val;
+	bool enabled;
 	int ret;
 
 	ret = strict_strtoul(buf, 10, &val);
@@ -74,6 +90,9 @@ static ssize_t iio_bfin_tmr_frequency_store(struct device *dev,
 		goto error_ret;
 	}
 
+	enabled = get_enabled_gptimers() & st->t->bit;
+
+	if (enabled)
 		disable_gptimers(st->t->bit);
 
 	if (!val)
@@ -87,6 +106,8 @@ static ssize_t iio_bfin_tmr_frequency_store(struct device *dev,
 
 	set_gptimer_period(st->t->id, val);
 	set_gptimer_pwidth(st->t->id, 1);
+
+	if (enabled)
 		enable_gptimers(st->t->bit);
 
 error_ret:
@@ -127,7 +148,6 @@ static const struct attribute_group *iio_bfin_tmr_trigger_attr_groups[] = {
 	NULL
 };
 
-
 static irqreturn_t iio_bfin_tmr_trigger_isr(int irq, void *devid)
 {
 	struct bfin_tmr_state *st = devid;
@@ -151,6 +171,7 @@ static int iio_bfin_tmr_get_number(int irq)
 
 static const struct iio_trigger_ops iio_bfin_tmr_trigger_ops = {
 	.owner = THIS_MODULE,
+	.set_trigger_state = iio_bfin_tmr_set_state,
 };
 
 static int __devinit iio_bfin_tmr_trigger_probe(struct platform_device *pdev)