iio: adc: spear_adc: Replace indio_dev->mlock with own device lock

As part of the general cleanup of indio_dev->mlock, this change replaces
it with a local lock on the device's state structure.

This is part of a bigger cleanup.
Link: https://lore.kernel.org/linux-iio/CA+U=Dsoo6YABe5ODLp+eFNPGFDjk5ZeQEceGkqjxXcVEhLWubw@mail.gmail.com/
Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
Signed-off-by: Mircea Caprioru <mircea.caprioru@analog.com>
Link: https://lore.kernel.org/r/20200928131333.36646-1-mircea.caprioru@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/spear_adc.c b/drivers/iio/adc/spear_adc.c
index 1bc986a..d93e580 100644 (file)
--- 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;
 
        /*