On Sat, 9 Mar 2019 18:37:01 +0000
Jonathan Cameron <jic23@xxxxxxxxxx> wrote:
> On Sat, 9 Mar 2019 17:29:36 +0100
> Tomasz Duszynski <tduszyns@xxxxxxxxx> wrote:
>
> > On Fri, Mar 08, 2019 at 02:03:27PM -0800, justinpopo6@xxxxxxxxx wrote:
> > > From: Justin Chen <justinpopo6@xxxxxxxxx>
> > >
> > > Indio->mlock is used for protecting the different iio device modes.
> > > It is currently not being used in this way. Replace the lock with
> > > an internal lock specifically used for protecting the SPI transfer
> > > buffer.
> > >
> > > Signed-off-by: Justin Chen <justinpopo6@xxxxxxxxx>
> > > ---
> > > drivers/iio/adc/ti-ads7950.c | 19 +++++++++++++++----
> > > 1 file changed, 15 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/iio/adc/ti-ads7950.c b/drivers/iio/adc/ti-ads7950.c
> > > index 0ad6359..1e47bef 100644
> > > --- a/drivers/iio/adc/ti-ads7950.c
> > > +++ b/drivers/iio/adc/ti-ads7950.c
> > > @@ -56,6 +56,9 @@ struct ti_ads7950_state {
> > > struct spi_message ring_msg;
> > > struct spi_message scan_single_msg;
> > >
> > > + /* Lock to protect the spi xfer buffers */
> > > + struct mutex slock;
> > > +
> > > struct regulator *reg;
> > > unsigned int vref_mv;
> > >
> > > @@ -268,6 +271,7 @@ static irqreturn_t ti_ads7950_trigger_handler(int irq, void *p)
> > > struct ti_ads7950_state *st = iio_priv(indio_dev);
> > > int ret;
> > >
> > > + mutex_lock(&st->slock);
> > > ret = spi_sync(st->spi, &st->ring_msg);
> > > if (ret < 0)
> > > goto out;
> > > @@ -276,6 +280,7 @@ static irqreturn_t ti_ads7950_trigger_handler(int irq, void *p)
> > > iio_get_time_ns(indio_dev));
> > >
> > > out:
> > > + mutex_unlock(&st->slock);
> > > iio_trigger_notify_done(indio_dev->trig);
> > >
> > > return IRQ_HANDLED;
> > > @@ -286,7 +291,7 @@ static int ti_ads7950_scan_direct(struct iio_dev *indio_dev, unsigned int ch)
> > > struct ti_ads7950_state *st = iio_priv(indio_dev);
> > > int ret, cmd;
> > >
> > > - mutex_lock(&indio_dev->mlock);
> > > + mutex_lock(&st->slock);
> > >
> > > cmd = TI_ADS7950_CR_WRITE | TI_ADS7950_CR_CHAN(ch) | st->settings;
> > > st->single_tx = cmd;
> > > @@ -298,7 +303,7 @@ static int ti_ads7950_scan_direct(struct iio_dev *indio_dev, unsigned int ch)
> > > ret = st->single_rx;
> > >
> > > out:
> > > - mutex_unlock(&indio_dev->mlock);
> > > + mutex_unlock(&st->slock);
> > >
> > > return ret;
> > > }
> > > @@ -432,16 +437,19 @@ static int ti_ads7950_probe(struct spi_device *spi)
> > > if (ACPI_COMPANION(&spi->dev))
> > > st->vref_mv = TI_ADS7950_VA_MV_ACPI_DEFAULT;
> > >
> > > + mutex_init(&st->slock);
> > > +
> > > st->reg = devm_regulator_get(&spi->dev, "vref");
> > > if (IS_ERR(st->reg)) {
> > > dev_err(&spi->dev, "Failed get get regulator \"vref\"\n");
> > > - return PTR_ERR(st->reg);
> > > + ret = PTR_ERR(st->reg);
> > > + goto error_destroy_mutex;
> > > }
> > >
> > > ret = regulator_enable(st->reg);
> > > if (ret) {
> > > dev_err(&spi->dev, "Failed to enable regulator \"vref\"\n");
> > > - return ret;
> > > + goto error_destroy_mutex;
> > > }
> > >
> > > ret = iio_triggered_buffer_setup(indio_dev, NULL,
> > > @@ -463,6 +471,8 @@ static int ti_ads7950_probe(struct spi_device *spi)
> > > iio_triggered_buffer_cleanup(indio_dev);
> > > error_disable_reg:
> > > regulator_disable(st->reg);
> > > +error_destroy_mutex:
> > > + mutex_destroy(&st->slock);
> >
> > If your intention was to do resources cleanup then this is not
> > what this api was designed for. This is actually for debugging unwanted
> > subsequent mutex usage.
>
> Yes. In a case like this where it is the last thing in a remove
> it adds little value as there should be nothing left to take the mutex
> anyway. This is the reason (I guess) there has never been a
> devm_mutex_init function to tidy this up automatically...
>
Having said that, I just realised I applied this anyway last week.
I'm not fussed enough about this to revert the change, so right
now the mutex_destroys are there.
Jonathan
> >
> > >
> > > return ret;
> > > }
> > > @@ -475,6 +485,7 @@ static int ti_ads7950_remove(struct spi_device *spi)
> > > iio_device_unregister(indio_dev);
> > > iio_triggered_buffer_cleanup(indio_dev);
> > > regulator_disable(st->reg);
> > > + mutex_destroy(&st->slock);
> > >
> > > return 0;
> > > }
> > > --
> > > 2.7.4
> > >
>
