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From:   Peter Ujfalusi <peter.ujfalusi@ti.com>
To:     <jic23@kernel.org>, <mcoquelin.stm32@gmail.com>,
        <alexandre.torgue@st.com>, <fabrice.gasnier@st.com>
CC:     <vkoul@kernel.org>, <linux-iio@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>,
        <linux-stm32@st-md-mailman.stormreply.com>
Subject: [PATCH v3] iio: adc: stm32-adc: Use dma_request_chan() instead dma_request_slave_channel()
Date:   Wed, 8 Jan 2020 10:08:01 +0200
Message-ID: <20200108080801.14144-1-peter.ujfalusi@ti.com>
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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>
---
Hi,

Changes since v2:
- Replace the comment as suggested by Fabrice

Changes since v1:
- Fall back to IRQ mode only in case of ENODEV

Regards,
Peter

 drivers/iio/adc/stm32-adc.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
index 3b291d72701c..a8d2414ee2eb 100644
--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -1746,9 +1746,21 @@ 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,
-- 
Peter

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
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