[PATCH] iio: adc: stm32-adc: fix stopping dma

[PATCH] iio: adc: stm32-adc: fix stopping dma

[Fabrice Gasnier]

There maybe a race when using dmaengine_terminate_all(). The predisable
routine may call iio_triggered_buffer_predisable() prior to a pending DMA
callback.
Adopt dmaengine_terminate_sync() to ensure there's no pending DMA request
before calling iio_triggered_buffer_predisable().

Fixes: 2763ea0585c9 ("iio: adc: stm32: add optional dma support")

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
---
 drivers/iio/adc/stm32-adc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
index 663f8a5..73aee59 100644
--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -1399,7 +1399,7 @@ static int stm32_adc_dma_start(struct iio_dev *indio_dev)
 	cookie = dmaengine_submit(desc);
 	ret = dma_submit_error(cookie);
 	if (ret) {
-		dmaengine_terminate_all(adc->dma_chan);
+		dmaengine_terminate_sync(adc->dma_chan);
 		return ret;
 	}
 
@@ -1477,7 +1477,7 @@ static void __stm32_adc_buffer_predisable(struct iio_dev *indio_dev)
 		stm32_adc_conv_irq_disable(adc);
 
 	if (adc->dma_chan)
-		dmaengine_terminate_all(adc->dma_chan);
+		dmaengine_terminate_sync(adc->dma_chan);
 
 	if (stm32_adc_set_trig(indio_dev, NULL))
 		dev_err(&indio_dev->dev, "Can't clear trigger\n");
-- 
2.7.4

Re: [PATCH] iio: adc: stm32-adc: fix stopping dma

[Jonathan Cameron]

On Fri, 25 Oct 2019 17:04:20 +0200
Fabrice Gasnier <fabrice.gasnier@st.com> wrote:

> There maybe a race when using dmaengine_terminate_all(). The predisable
> routine may call iio_triggered_buffer_predisable() prior to a pending DMA
> callback.
> Adopt dmaengine_terminate_sync() to ensure there's no pending DMA request
> before calling iio_triggered_buffer_predisable().
> 
> Fixes: 2763ea0585c9 ("iio: adc: stm32: add optional dma support")
> 
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Applied to the fixes-togreg branch of iio.git and marked for stable.
I'm guessing this is not something that has been observed in practice, but
seems like a safe fix anyway to backport.

Thanks,

Jonathan

> ---
>  drivers/iio/adc/stm32-adc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
> index 663f8a5..73aee59 100644
> --- a/drivers/iio/adc/stm32-adc.c
> +++ b/drivers/iio/adc/stm32-adc.c
> @@ -1399,7 +1399,7 @@ static int stm32_adc_dma_start(struct iio_dev *indio_dev)
>  	cookie = dmaengine_submit(desc);
>  	ret = dma_submit_error(cookie);
>  	if (ret) {
> -		dmaengine_terminate_all(adc->dma_chan);
> +		dmaengine_terminate_sync(adc->dma_chan);
>  		return ret;
>  	}
>  
> @@ -1477,7 +1477,7 @@ static void __stm32_adc_buffer_predisable(struct iio_dev *indio_dev)
>  		stm32_adc_conv_irq_disable(adc);
>  
>  	if (adc->dma_chan)
> -		dmaengine_terminate_all(adc->dma_chan);
> +		dmaengine_terminate_sync(adc->dma_chan);
>  
>  	if (stm32_adc_set_trig(indio_dev, NULL))
>  		dev_err(&indio_dev->dev, "Can't clear trigger\n");