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path: root/drivers/iio/adc/spear_adc.c
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Diffstat (limited to 'drivers/iio/adc/spear_adc.c')
-rw-r--r--drivers/iio/adc/spear_adc.c20
1 files changed, 16 insertions, 4 deletions
diff --git a/drivers/iio/adc/spear_adc.c b/drivers/iio/adc/spear_adc.c
index 1bc986a7009d..d93e580b3dc5 100644
--- a/drivers/iio/adc/spear_adc.c
+++ b/drivers/iio/adc/spear_adc.c
@@ -75,6 +75,15 @@ struct spear_adc_state {
struct adc_regs_spear6xx __iomem *adc_base_spear6xx;
struct clk *clk;
struct completion completion;
+ /*
+ * Lock to protect the device state during a potential concurrent
+ * read access from userspace. Reading a raw value requires a sequence
+ * of register writes, then a wait for a completion callback,
+ * and finally a register read, during which userspace could issue
+ * another read request. This lock protects a read access from
+ * ocurring before another one has finished.
+ */
+ struct mutex lock;
u32 current_clk;
u32 sampling_freq;
u32 avg_samples;
@@ -146,7 +155,7 @@ static int spear_adc_read_raw(struct iio_dev *indio_dev,
switch (mask) {
case IIO_CHAN_INFO_RAW:
- mutex_lock(&indio_dev->mlock);
+ mutex_lock(&st->lock);
status = SPEAR_ADC_STATUS_CHANNEL_NUM(chan->channel) |
SPEAR_ADC_STATUS_AVG_SAMPLE(st->avg_samples) |
@@ -159,7 +168,7 @@ static int spear_adc_read_raw(struct iio_dev *indio_dev,
wait_for_completion(&st->completion); /* set by ISR */
*val = st->value;
- mutex_unlock(&indio_dev->mlock);
+ mutex_unlock(&st->lock);
return IIO_VAL_INT;
@@ -187,7 +196,7 @@ static int spear_adc_write_raw(struct iio_dev *indio_dev,
if (mask != IIO_CHAN_INFO_SAMP_FREQ)
return -EINVAL;
- mutex_lock(&indio_dev->mlock);
+ mutex_lock(&st->lock);
if ((val < SPEAR_ADC_CLK_MIN) ||
(val > SPEAR_ADC_CLK_MAX) ||
@@ -199,7 +208,7 @@ static int spear_adc_write_raw(struct iio_dev *indio_dev,
spear_adc_set_clk(st, val);
out:
- mutex_unlock(&indio_dev->mlock);
+ mutex_unlock(&st->lock);
return ret;
}
@@ -271,6 +280,9 @@ static int spear_adc_probe(struct platform_device *pdev)
}
st = iio_priv(indio_dev);
+
+ mutex_init(&st->lock);
+
st->np = np;
/*