Re: [PATCH v2] iio: adc: stm32-adc: fix sleep in atomic context

[Jonathan Cameron]

On Mon, 9 Mar 2020 11:39:17 +0100
Fabrice Gasnier <fabrice.gasnier@xxxxxx> wrote:

> On 3/9/20 11:02 AM, Olivier Moysan wrote:
> > This commit fixes the following error:
> > "BUG: sleeping function called from invalid context at kernel/irq/chip.c"
> > 
> > In DMA mode suppress the trigger irq handler, and make the buffer
> > transfers directly in DMA callback, instead.
> > 
> > Fixes: 2763ea0585c9 ("iio: adc: stm32: add optional dma support")
> > 
> > Signed-off-by: Olivier Moysan <olivier.moysan@xxxxxx>  
> 
> Hi Olivier,
> 
> Acked-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx>
Thanks.  Queued up locally but not pushed out just yet as I have a pull
request out to Greg.  Also marked for stable.

thanks,

Jonathan

> 
> Thanks,
> Fabrice
> 
> > ---
> > Changes in v2:
> > - Add "Fixes" tag in commit message
> > 
> > This solution has been already discussed in the thread
> > https://lkml.org/lkml/2019/3/30/171, and applied in STM32 DFSDM driver:
> > e19ac9d9a978 ("iio: adc: stm32-dfsdm: fix sleep in atomic context")
> > ---
> >  drivers/iio/adc/stm32-adc.c | 31 ++++++++++++++++++++++++++++---
> >  1 file changed, 28 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
> > index 80c3f963527b..ae622ee6d08c 100644
> > --- a/drivers/iio/adc/stm32-adc.c
> > +++ b/drivers/iio/adc/stm32-adc.c
> > @@ -1418,8 +1418,30 @@ static unsigned int stm32_adc_dma_residue(struct stm32_adc *adc)
> >  static void stm32_adc_dma_buffer_done(void *data)
> >  {
> >  	struct iio_dev *indio_dev = data;
> > +	struct stm32_adc *adc = iio_priv(indio_dev);
> > +	int residue = stm32_adc_dma_residue(adc);
> > +
> > +	/*
> > +	 * In DMA mode the trigger services of IIO are not used
> > +	 * (e.g. no call to iio_trigger_poll).
> > +	 * Calling irq handler associated to the hardware trigger is not
> > +	 * relevant as the conversions have already been done. Data
> > +	 * transfers are performed directly in DMA callback instead.
> > +	 * This implementation avoids to call trigger irq handler that
> > +	 * may sleep, in an atomic context (DMA irq handler context).
> > +	 */
> > +	dev_dbg(&indio_dev->dev, "%s bufi=%d\n", __func__, adc->bufi);
> >  
> > -	iio_trigger_poll_chained(indio_dev->trig);
> > +	while (residue >= indio_dev->scan_bytes) {
> > +		u16 *buffer = (u16 *)&adc->rx_buf[adc->bufi];
> > +
> > +		iio_push_to_buffers(indio_dev, buffer);
> > +
> > +		residue -= indio_dev->scan_bytes;
> > +		adc->bufi += indio_dev->scan_bytes;
> > +		if (adc->bufi >= adc->rx_buf_sz)
> > +			adc->bufi = 0;
> > +	}
> >  }
> >  
> >  static int stm32_adc_dma_start(struct iio_dev *indio_dev)
> > @@ -1845,6 +1867,7 @@ static int stm32_adc_probe(struct platform_device *pdev)
> >  {
> >  	struct iio_dev *indio_dev;
> >  	struct device *dev = &pdev->dev;
> > +	irqreturn_t (*handler)(int irq, void *p) = NULL;
> >  	struct stm32_adc *adc;
> >  	int ret;
> >  
> > @@ -1911,9 +1934,11 @@ static int stm32_adc_probe(struct platform_device *pdev)
> >  	if (ret < 0)
> >  		return ret;
> >  
> > +	if (!adc->dma_chan)
> > +		handler = &stm32_adc_trigger_handler;
> > +
> >  	ret = iio_triggered_buffer_setup(indio_dev,
> > -					 &iio_pollfunc_store_time,
> > -					 &stm32_adc_trigger_handler,
> > +					 &iio_pollfunc_store_time, handler,
> >  					 &stm32_adc_buffer_setup_ops);
> >  	if (ret) {
> >  		dev_err(&pdev->dev, "buffer setup failed\n");
> >