iio: dln2-adc: Fix lockdep complaint

When reading the voltage:

$ cat /sys/bus/iio/devices/iio\:device0/in_voltage0_raw

Lockdep complains:

[  153.910616] ======================================================
[  153.916918] WARNING: possible circular locking dependency detected
[  153.923221] 5.14.0+ #5 Not tainted
[  153.926692] ------------------------------------------------------
[  153.932992] cat/717 is trying to acquire lock:
[  153.937525] c2585358 (&indio_dev->mlock){+.+.}-{3:3}, at: iio_device_claim_direct_mode+0x28/0x44
[  153.946541]
               but task is already holding lock:
[  153.952487] c2585860 (&dln2->mutex){+.+.}-{3:3}, at: dln2_adc_read_raw+0x94/0x2bc [dln2_adc]
[  153.961152]
               which lock already depends on the new lock.

Fix this by not calling into the iio core underneath the dln2->mutex lock.

Fixes: 7c0299e879dd ("iio: adc: Add support for DLN2 ADC")
Cc: Jack Andersen <jackoalan@gmail.com>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://lore.kernel.org/r/20211018113731.25723-1-noralf@tronnes.org
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/dln2-adc.c b/drivers/iio/adc/dln2-adc.c
index 1640766..6c67192 100644 (file)
--- a/drivers/iio/adc/dln2-adc.c
+++ b/drivers/iio/adc/dln2-adc.c
@@ -248,7 +248,6 @@ static int dln2_adc_set_chan_period(struct dln2_adc *dln2,
 static int dln2_adc_read(struct dln2_adc *dln2, unsigned int channel)
 {
        int ret, i;
-       struct iio_dev *indio_dev = platform_get_drvdata(dln2->pdev);
        u16 conflict;
        __le16 value;
        int olen = sizeof(value);
@@ -257,13 +256,9 @@ static int dln2_adc_read(struct dln2_adc *dln2, unsigned int channel)
                .chan = channel,
        };
 
-       ret = iio_device_claim_direct_mode(indio_dev);
-       if (ret < 0)
-               return ret;
-
        ret = dln2_adc_set_chan_enabled(dln2, channel, true);
        if (ret < 0)
-               goto release_direct;
+               return ret;
 
        ret = dln2_adc_set_port_enabled(dln2, true, &conflict);
        if (ret < 0) {
@@ -300,8 +295,6 @@ disable_port:
        dln2_adc_set_port_enabled(dln2, false, NULL);
 disable_chan:
        dln2_adc_set_chan_enabled(dln2, channel, false);
-release_direct:
-       iio_device_release_direct_mode(indio_dev);
 
        return ret;
 }
@@ -337,10 +330,16 @@ static int dln2_adc_read_raw(struct iio_dev *indio_dev,
 
        switch (mask) {
        case IIO_CHAN_INFO_RAW:
+               ret = iio_device_claim_direct_mode(indio_dev);
+               if (ret < 0)
+                       return ret;
+
                mutex_lock(&dln2->mutex);
                ret = dln2_adc_read(dln2, chan->channel);
                mutex_unlock(&dln2->mutex);
 
+               iio_device_release_direct_mode(indio_dev);
+
                if (ret < 0)
                        return ret;