[PATCH v2] iio: adc: exynos_adc: Replace indio_dev->mlock with own device lock

From: Alexandru Ardelean
Date: Wed Sep 16 2020 - 05:32:07 EST


From: Sergiu Cuciurean <sergiu.cuciurean@xxxxxxxxxx>

As part of the general cleanup of indio_dev->mlock, this change replaces
it with a local lock, to protect potential concurrent access to the
completion callback during a conversion.

This is part of a bigger cleanup.
Link: https://lore.kernel.org/linux-iio/CA+U=Dsoo6YABe5ODLp+eFNPGFDjk5ZeQEceGkqjxXcVEhLWubw@xxxxxxxxxxxxxx/

Reviewed-by: Krzysztof Kozlowski <krzk@xxxxxxxxxx>
Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@xxxxxxxxxx>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
---
drivers/iio/adc/exynos_adc.c | 20 ++++++++++++++++----
1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/adc/exynos_adc.c b/drivers/iio/adc/exynos_adc.c
index 20477b249f2a..99f4404e9fd1 100644
--- a/drivers/iio/adc/exynos_adc.c
+++ b/drivers/iio/adc/exynos_adc.c
@@ -138,6 +138,16 @@ struct exynos_adc {
bool read_ts;
u32 ts_x;
u32 ts_y;
+
+ /*
+ * Lock to protect from potential concurrent access to the
+ * completion callback during a manual conversion. For this driver
+ * a wait-callback is used to wait for the conversion result,
+ * so in the meantime no other read request (or conversion start)
+ * must be performed, otherwise it would interfere with the
+ * current conversion result.
+ */
+ struct mutex lock;
};

struct exynos_adc_data {
@@ -542,7 +552,7 @@ static int exynos_read_raw(struct iio_dev *indio_dev,
return -EINVAL;
}

- mutex_lock(&indio_dev->mlock);
+ mutex_lock(&info->lock);
reinit_completion(&info->completion);

/* Select the channel to be used and Trigger conversion */
@@ -562,7 +572,7 @@ static int exynos_read_raw(struct iio_dev *indio_dev,
ret = IIO_VAL_INT;
}

- mutex_unlock(&indio_dev->mlock);
+ mutex_unlock(&info->lock);

return ret;
}
@@ -573,7 +583,7 @@ static int exynos_read_s3c64xx_ts(struct iio_dev *indio_dev, int *x, int *y)
unsigned long timeout;
int ret;

- mutex_lock(&indio_dev->mlock);
+ mutex_lock(&info->lock);
info->read_ts = true;

reinit_completion(&info->completion);
@@ -598,7 +608,7 @@ static int exynos_read_s3c64xx_ts(struct iio_dev *indio_dev, int *x, int *y)
}

info->read_ts = false;
- mutex_unlock(&indio_dev->mlock);
+ mutex_unlock(&info->lock);

return ret;
}
@@ -868,6 +878,8 @@ static int exynos_adc_probe(struct platform_device *pdev)
indio_dev->channels = exynos_adc_iio_channels;
indio_dev->num_channels = info->data->num_channels;

+ mutex_init(&info->lock);
+
ret = request_irq(info->irq, exynos_adc_isr,
0, dev_name(&pdev->dev), info);
if (ret < 0) {
--
2.17.1