iio: adc: stm32-adc: Use dma_request_chan() instead dma_request_slave_channel()

dma_request_slave_channel() is a wrapper on top of dma_request_chan()
eating up the error code.

By using dma_request_chan() directly the driver can support deferred
probing against DMA.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
index 5f05bf9..80c3f96 100644 (file)
--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -1796,9 +1796,21 @@ static int stm32_adc_dma_request(struct iio_dev *indio_dev)
        struct dma_slave_config config;
        int ret;
 
-       adc->dma_chan = dma_request_slave_channel(&indio_dev->dev, "rx");
-       if (!adc->dma_chan)
+       adc->dma_chan = dma_request_chan(&indio_dev->dev, "rx");
+       if (IS_ERR(adc->dma_chan)) {
+               ret = PTR_ERR(adc->dma_chan);
+               if (ret != -ENODEV) {
+                       if (ret != -EPROBE_DEFER)
+                               dev_err(&indio_dev->dev,
+                                       "DMA channel request failed with %d\n",
+                                       ret);
+                       return ret;
+               }
+
+               /* DMA is optional: fall back to IRQ mode */
+               adc->dma_chan = NULL;
                return 0;
+       }
 
        adc->rx_buf = dma_alloc_coherent(adc->dma_chan->device->dev,
                                         STM32_DMA_BUFFER_SIZE,