Second round of IIO fixes for the 3.11 cycle.

1) Fix a long term race in the IIO trigger handling.
    This only effects cases where a single trigger is in use
    by multiple devices.
 2) ti_am335x fix an issue with incorrect data due to reading before
    the sequencer is finished.
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Merge tag 'iio-fixes-for-3.11b' of git://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio into staging-linus

Jonathan writes:

Second round of IIO fixes for the 3.11 cycle.

1) Fix a long term race in the IIO trigger handling.
   This only effects cases where a single trigger is in use
   by multiple devices.
2) ti_am335x fix an issue with incorrect data due to reading before
   the sequencer is finished.

drivers/iio/adc/ti_am335x_adc.c

@@ -60,7 +60,6 @@ static void tiadc_step_config(struct tiadc_device *adc_dev)
 {
 	unsigned int stepconfig;
 	int i, steps;
-	u32 step_en;
 
 	/*
 	 * There are 16 configurable steps and 8 analog input
@@ -86,8 +85,7 @@ static void tiadc_step_config(struct tiadc_device *adc_dev)
 		adc_dev->channel_step[i] = steps;
 		steps++;
 	}
-	step_en = get_adc_step_mask(adc_dev);
-	am335x_tsc_se_set(adc_dev->mfd_tscadc, step_en);
+
 }
 
 static const char * const chan_name_ain[] = {
@@ -142,10 +140,22 @@ static int tiadc_read_raw(struct iio_dev *indio_dev,
 		int *val, int *val2, long mask)
 {
 	struct tiadc_device *adc_dev = iio_priv(indio_dev);
-	int i;
-	unsigned int fifo1count, read;
+	int i, map_val;
+	unsigned int fifo1count, read, stepid;
 	u32 step = UINT_MAX;
 	bool found = false;
+	u32 step_en;
+	unsigned long timeout = jiffies + usecs_to_jiffies
+				(IDLE_TIMEOUT * adc_dev->channels);
+	step_en = get_adc_step_mask(adc_dev);
+	am335x_tsc_se_set(adc_dev->mfd_tscadc, step_en);
+
+	/* Wait for ADC sequencer to complete sampling */
+	while (tiadc_readl(adc_dev, REG_ADCFSM) & SEQ_STATUS) {
+		if (time_after(jiffies, timeout))
+			return -EAGAIN;
+		}
+	map_val = chan->channel + TOTAL_CHANNELS;
 
 	/*
 	 * When the sub-system is first enabled,
@@ -170,12 +180,16 @@ static int tiadc_read_raw(struct iio_dev *indio_dev,
 	fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT);
 	for (i = 0; i < fifo1count; i++) {
 		read = tiadc_readl(adc_dev, REG_FIFO1);
-		if (read >> 16 == step) {
-			*val = read & 0xfff;
+		stepid = read & FIFOREAD_CHNLID_MASK;
+		stepid = stepid >> 0x10;
+
+		if (stepid == map_val) {
+			read = read & FIFOREAD_DATA_MASK;
 			found = true;
+			*val = read;
 		}
 	}
-	am335x_tsc_se_update(adc_dev->mfd_tscadc);
+
 	if (found == false)
 		return -EBUSY;
 	return IIO_VAL_INT;

drivers/iio/industrialio-trigger.c

@@ -127,12 +127,17 @@ static struct iio_trigger *iio_trigger_find_by_name(const char *name,
 void iio_trigger_poll(struct iio_trigger *trig, s64 time)
 {
 	int i;
-	if (!trig->use_count)
-		for (i = 0; i < CONFIG_IIO_CONSUMERS_PER_TRIGGER; i++)
-			if (trig->subirqs[i].enabled) {
-				trig->use_count++;
+
+	if (!atomic_read(&trig->use_count)) {
+		atomic_set(&trig->use_count, CONFIG_IIO_CONSUMERS_PER_TRIGGER);
+
+		for (i = 0; i < CONFIG_IIO_CONSUMERS_PER_TRIGGER; i++) {
+			if (trig->subirqs[i].enabled)
 				generic_handle_irq(trig->subirq_base + i);
-			}
+			else
+				iio_trigger_notify_done(trig);
+		}
+	}
 }
 EXPORT_SYMBOL(iio_trigger_poll);
 
@@ -146,19 +151,24 @@ EXPORT_SYMBOL(iio_trigger_generic_data_rdy_poll);
 void iio_trigger_poll_chained(struct iio_trigger *trig, s64 time)
 {
 	int i;
-	if (!trig->use_count)
-		for (i = 0; i < CONFIG_IIO_CONSUMERS_PER_TRIGGER; i++)
-			if (trig->subirqs[i].enabled) {
-				trig->use_count++;
+
+	if (!atomic_read(&trig->use_count)) {
+		atomic_set(&trig->use_count, CONFIG_IIO_CONSUMERS_PER_TRIGGER);
+
+		for (i = 0; i < CONFIG_IIO_CONSUMERS_PER_TRIGGER; i++) {
+			if (trig->subirqs[i].enabled)
 				handle_nested_irq(trig->subirq_base + i);
-			}
+			else
+				iio_trigger_notify_done(trig);
+		}
+	}
 }
 EXPORT_SYMBOL(iio_trigger_poll_chained);
 
 void iio_trigger_notify_done(struct iio_trigger *trig)
 {
-	trig->use_count--;
-	if (trig->use_count == 0 && trig->ops && trig->ops->try_reenable)
+	if (atomic_dec_and_test(&trig->use_count) && trig->ops &&
+		trig->ops->try_reenable)
 		if (trig->ops->try_reenable(trig))
 			/* Missed an interrupt so launch new poll now */
 			iio_trigger_poll(trig, 0);

include/linux/iio/trigger.h

@@ -8,6 +8,7 @@
  */
 #include <linux/irq.h>
 #include <linux/module.h>
+#include <linux/atomic.h>
 
 #ifndef _IIO_TRIGGER_H_
 #define _IIO_TRIGGER_H_
@@ -61,7 +62,7 @@ struct iio_trigger {
 
 	struct list_head		list;
 	struct list_head		alloc_list;
-	int use_count;
+	atomic_t			use_count;
 
 	struct irq_chip			subirq_chip;
 	int				subirq_base;

include/linux/mfd/ti_am335x_tscadc.h

@@ -113,11 +113,27 @@
 #define CNTRLREG_8WIRE		CNTRLREG_AFE_CTRL(3)
 #define CNTRLREG_TSCENB		BIT(7)
 
+/* FIFO READ Register */
+#define FIFOREAD_DATA_MASK (0xfff << 0)
+#define FIFOREAD_CHNLID_MASK (0xf << 16)
+
+/* Sequencer Status */
+#define SEQ_STATUS BIT(5)
+
 #define ADC_CLK			3000000
 #define	MAX_CLK_DIV		7
 #define TOTAL_STEPS		16
 #define TOTAL_CHANNELS		8
 
+/*
+* ADC runs at 3MHz, and it takes
+* 15 cycles to latch one data output.
+* Hence the idle time for ADC to
+* process one sample data would be
+* around 5 micro seconds.
+*/
+#define IDLE_TIMEOUT 5 /* microsec */
+
 #define TSCADC_CELLS		2
 
 struct ti_tscadc_dev {