Patch "iio: adc: ti_am335x_adc: Protect FIFO1 from concurrent access" has been added to the 4.7-stable tree

This is a note to let you know that I've just added the patch titled

iio: adc: ti_am335x_adc: Protect FIFO1 from concurrent access

to the 4.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
iio-adc-ti_am335x_adc-protect-fifo1-from-concurrent-access.patch
and it can be found in the queue-4.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Vignesh R <[email protected]>
Date: Wed, 17 Aug 2016 17:43:00 +0530
Subject: iio: adc: ti_am335x_adc: Protect FIFO1 from concurrent access

From: Vignesh R <[email protected]>

commit 90c43ec6997a892448f1f86180a515f59cafd8a3 upstream.

It is possible that two or more ADC channels can be simultaneously requested for raw samples, in which case there can be race in access to FIFO data resulting in loss of samples.
If am335x_tsc_se_set_once() is called again from tiadc_read_raw(), when ADC is still acquired to sample one of the channels, the second process might be put into uninterruptible sleep state. Fix these issues, by protecting FIFO access and channel configurations with a mutex. Since tiadc_read_raw() might take anywhere between few microseconds to few milliseconds to finish execution (depending on averaging and delay values supplied via DT), its better to use mutex instead of spinlock.

---
 drivers/iio/adc/ti_am335x_adc.c |   14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

@@ -32,6 +32,7 @@
 
 struct tiadc_device {
 	struct ti_tscadc_dev *mfd_tscadc;
+	struct mutex fifo1_lock; /* to protect fifo access */
 	int channels;
 	u8 channel_line[8];
 	u8 channel_step[8];

@@ -360,6 +361,7 @@ static int tiadc_read_raw(struct iio_dev
 		int *val, int *val2, long mask)
 {
 	struct tiadc_device *adc_dev = iio_priv(indio_dev);
+	int ret = IIO_VAL_INT;
 	int i, map_val;
 	unsigned int fifo1count, read, stepid;
 	bool found = false;

@@ -373,6 +375,7 @@ static int tiadc_read_raw(struct iio_dev
 	if (!step_en)
 		return -EINVAL;
 
+	mutex_lock(&adc_dev->fifo1_lock);
 	fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT);
 	while (fifo1count--)
 		tiadc_readl(adc_dev, REG_FIFO1);

@@ -389,7 +392,8 @@ static int tiadc_read_raw(struct iio_dev
 
 		if (time_after(jiffies, timeout)) {
 			am335x_tsc_se_adc_done(adc_dev->mfd_tscadc);
-			return -EAGAIN;
+			ret = -EAGAIN;
+			goto err_unlock;
 		}
 	}
 	map_val = adc_dev->channel_step[chan->scan_index];

@@ -415,8 +419,11 @@ static int tiadc_read_raw(struct iio_dev
 	am335x_tsc_se_adc_done(adc_dev->mfd_tscadc);
 
 	if (found == false)
-		return -EBUSY;
-	return IIO_VAL_INT;
+		ret =  -EBUSY;
+
+err_unlock:
+	mutex_unlock(&adc_dev->fifo1_lock);
+	return ret;
 }
 
 static const struct iio_info tiadc_info = {

@@ -485,6 +492,7 @@ static int tiadc_probe(struct platform_d
 
 	tiadc_step_config(indio_dev);
 	tiadc_writel(adc_dev, REG_FIFO1THR, FIFO1_THRESHOLD);
+	mutex_init(&adc_dev->fifo1_lock);
 
 	err = tiadc_channel_init(indio_dev, adc_dev->channels);
 	if (err < 0)

Patches currently in stable-queue which might be from [email protected] are

queue-4.7/iio-adc-ti_am335x_adc-protect-fifo1-from-concurrent-access.patch queue-4.7/iio-adc-ti_am335x_adc-increase-timeout-value-waiting-for-adc-sample.patch