linux-kernel - [PATCH v2 03/19] iio: adc: at91-sama5d2_adc: lock around oversampling and sample freq

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Message-ID: <20220628151631.3116454-4-claudiu.beznea@microchip.com>
Date:   Tue, 28 Jun 2022 18:16:15 +0300
From:   Claudiu Beznea <claudiu.beznea@...rochip.com>
To:     <eugen.hristev@...rochip.com>, <jic23@...nel.org>,
        <lars@...afoo.de>, <nicolas.ferre@...rochip.com>,
        <alexandre.belloni@...tlin.com>, <claudiu.beznea@...rochip.com>,
        <robh+dt@...nel.org>, <krzk+dt@...nel.org>
CC:     <linux-iio@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: [PATCH v2 03/19] iio: adc: at91-sama5d2_adc: lock around oversampling and sample freq

.read_raw()/.write_raw() could be called asynchronously from user space
or other in kernel drivers. Without locking on st->lock these could be
called asynchronously while there is a conversion in progress. Read will
be harmless but changing registers while conversion is in progress may
lead to inconsistent results. Thus, to avoid this lock st->lock.

Fixes: 27e177190891 ("iio:adc:at91_adc8xx: introduce new atmel adc driver")
Fixes: 6794e23fa3fe ("iio: adc: at91-sama5d2_adc: add support for oversampling resolution")
Signed-off-by: Claudiu Beznea <claudiu.beznea@...rochip.com>
---
 drivers/iio/adc/at91-sama5d2_adc.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
index c3301c749164..40a95d2fd5c8 100644
--- a/drivers/iio/adc/at91-sama5d2_adc.c
+++ b/drivers/iio/adc/at91-sama5d2_adc.c
@@ -1542,10 +1542,10 @@ static int at91_adc_read_info_raw(struct iio_dev *indio_dev,
 		ret = at91_adc_read_position(st, chan->channel,
 					     &tmp_val);
 		*val = tmp_val;
-		mutex_unlock(&st->lock);
-		iio_device_release_direct_mode(indio_dev);
 		if (ret > 0)
 			ret = at91_adc_adjust_val_osr(st, val);
+		mutex_unlock(&st->lock);
+		iio_device_release_direct_mode(indio_dev);
 
 		return ret;
 	}
@@ -1558,10 +1558,10 @@ static int at91_adc_read_info_raw(struct iio_dev *indio_dev,
 		ret = at91_adc_read_pressure(st, chan->channel,
 					     &tmp_val);
 		*val = tmp_val;
-		mutex_unlock(&st->lock);
-		iio_device_release_direct_mode(indio_dev);
 		if (ret > 0)
 			ret = at91_adc_adjust_val_osr(st, val);
+		mutex_unlock(&st->lock);
+		iio_device_release_direct_mode(indio_dev);
 
 		return ret;
 	}
@@ -1650,16 +1650,20 @@ static int at91_adc_write_raw(struct iio_dev *indio_dev,
 		/* if no change, optimize out */
 		if (val == st->oversampling_ratio)
 			return 0;
+		mutex_lock(&st->lock);
 		st->oversampling_ratio = val;
 		/* update ratio */
 		at91_adc_config_emr(st);
+		mutex_unlock(&st->lock);
 		return 0;
 	case IIO_CHAN_INFO_SAMP_FREQ:
 		if (val < st->soc_info.min_sample_rate ||
 		    val > st->soc_info.max_sample_rate)
 			return -EINVAL;
 
+		mutex_lock(&st->lock);
 		at91_adc_setup_samp_freq(indio_dev, val);
+		mutex_unlock(&st->lock);
 		return 0;
 	default:
 		return -EINVAL;
-- 
2.34.1