[PATCH AUTOSEL 4.14 02/27] iio: adc: stm32-adc: fix sleep in atomic context

Sasha Levin
2020-04-30T14:01:04Z

From: Olivier Moysan <olivier.moysan@st.com>

[ Upstream commit e2042d2936dfc84e9c600fe9b9d0039ca0e54b7d ]

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@st.com>
Acked-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 258a4712167a2..3cfb2d4b24412 100644
--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -1311,8 +1311,30 @@ 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)
@@ -1648,6 +1670,7 @@ 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;

@@ -1730,9 +1753,11 @@ static int stm32_adc_probe(struct platform_device *pdev)
if (ret < 0)
goto err_clk_disable;

+ 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");
--
2.20.1