On 5/16/20 5:35 PM, Jonathan Cameron wrote:
> On Thu, 14 May 2020 11:50:12 +0300
> Sergiu Cuciurean <sergiu.cuciurean@xxxxxxxxxx> wrote:
>
>> As part of the general cleanup of indio_dev->mlock, this change replaces
>> it with a local lock on the device's state structure.
>>
>> Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@xxxxxxxxxx>
>> ---
>> drivers/iio/dac/stm32-dac.c | 12 ++++++++----
>> 1 file changed, 8 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
>> index f22c1d9129b2..74b9474c8590 100644
>> --- a/drivers/iio/dac/stm32-dac.c
>> +++ b/drivers/iio/dac/stm32-dac.c
>> @@ -26,9 +26,11 @@
>> /**
>> * struct stm32_dac - private data of DAC driver
>> * @common: reference to DAC common data
>> + * @lock: lock to protect the data buffer during regmap ops
>
> In this particular case I'm not sure that's what mlock was being used for.
> I think it's about avoiding races around checking if powered down and
> actually doing it.
Hi Sergiu,
Indeed, purpose is to protect against a race here when reading CR, and
updating it via regmap (this also makes the subsequent pm_runtime calls
to be balanced based on this).
(Side note: there is no data buffer involved for the DAC.)
Could you please update the comment ?
Thanks,
Fabrice
>
>
>> */
>> struct stm32_dac {
>> struct stm32_dac_common *common;
>> + struct mutex lock;
>> };
>>
>> static int stm32_dac_is_enabled(struct iio_dev *indio_dev, int channel)
>> @@ -58,10 +60,10 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
>> int ret;
>>
>> /* already enabled / disabled ? */
>> - mutex_lock(&indio_dev->mlock);
>> + mutex_lock(&dac->lock);
>> ret = stm32_dac_is_enabled(indio_dev, ch);
>> if (ret < 0 || enable == !!ret) {
>> - mutex_unlock(&indio_dev->mlock);
>> + mutex_unlock(&dac->lock);
>> return ret < 0 ? ret : 0;
>> }
>>
>> @@ -69,13 +71,13 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
>> ret = pm_runtime_get_sync(dev);
>> if (ret < 0) {
>> pm_runtime_put_noidle(dev);
>> - mutex_unlock(&indio_dev->mlock);
>> + mutex_unlock(&dac->lock);
>> return ret;
>> }
>> }
>>
>> ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, msk, en);
>> - mutex_unlock(&indio_dev->mlock);
>> + mutex_unlock(&dac->lock);
>> if (ret < 0) {
>> dev_err(&indio_dev->dev, "%s failed\n", en ?
>> "Enable" : "Disable");
>> @@ -328,6 +330,8 @@ static int stm32_dac_probe(struct platform_device *pdev)
>> indio_dev->info = &stm32_dac_iio_info;
>> indio_dev->modes = INDIO_DIRECT_MODE;
>>
>> + mutex_init(&dac->lock);
>> +
>> ret = stm32_dac_chan_of_init(indio_dev);
>> if (ret < 0)
>> return ret;
>
