[PATCH 5/5] iio: adc: rockchip_saradc: Replace indio_dev->mlock with own device lock

Mircea Caprioru
2020-09-28T13:14:36Z

From: Sergiu Cuciurean <sergiu.cuciurean@analog.com>

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>
---
drivers/iio/adc/rockchip_saradc.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/adc/rockchip_saradc.c b/drivers/iio/adc/rockchip_saradc.c
index 1f3d7d639d37..80084c526cc6 100644
--- a/drivers/iio/adc/rockchip_saradc.c
+++ b/drivers/iio/adc/rockchip_saradc.c
@@ -53,6 +53,15 @@ struct rockchip_saradc {
const struct rockchip_saradc_data *data;
u16 last_val;
const struct iio_chan_spec *last_chan;
+ /*
+ * 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;
};

static void rockchip_saradc_power_down(struct rockchip_saradc *info)
@@ -92,17 +101,17 @@ static int rockchip_saradc_read_raw(struct iio_dev *indio_dev,

switch (mask) {
case IIO_CHAN_INFO_RAW:
- mutex_lock(&indio_dev->mlock);
+ mutex_lock(&info->lock);

ret = rockchip_saradc_conversion(info, chan);
if (ret) {
rockchip_saradc_power_down(info);
- mutex_unlock(&indio_dev->mlock);
+ mutex_unlock(&info->lock);
return ret;
}

*val = info->last_val;
- mutex_unlock(&indio_dev->mlock);
+ mutex_unlock(&info->lock);
return IIO_VAL_INT;
case IIO_CHAN_INFO_SCALE:
ret = regulator_get_voltage(info->vref);
@@ -254,7 +263,7 @@ static irqreturn_t rockchip_saradc_trigger_handler(int irq, void *p)
int ret;
int i, j = 0;

- mutex_lock(&i_dev->mlock);
+ mutex_lock(&info->lock);

for_each_set_bit(i, i_dev->active_scan_mask, i_dev->masklength) {
const struct iio_chan_spec *chan = &i_dev->channels[i];
@@ -271,7 +280,7 @@ static irqreturn_t rockchip_saradc_trigger_handler(int irq, void *p)

iio_push_to_buffers_with_timestamp(i_dev, &data, iio_get_time_ns(i_dev));
out:
- mutex_unlock(&i_dev->mlock);
+ mutex_unlock(&info->lock);

iio_trigger_notify_done(i_dev->trig);

@@ -332,6 +341,8 @@ static int rockchip_saradc_probe(struct platform_device *pdev)
info->reset = NULL;
}

+ mutex_init(&info->lock);
+
init_completion(&info->completion);

irq = platform_get_irq(pdev, 0);
--
2.25.1