linux-kernel - [PATCH 02/12] media: stm32: dcmi: perform dmaengine_slave

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Message-ID: <20251218-stm32-dcmi-dma-chaining-v1-2-39948ca6cbf6@foss.st.com>
Date: Thu, 18 Dec 2025 19:44:42 +0100
From: Alain Volmat <alain.volmat@...s.st.com>
To: Hugues Fruchet <hugues.fruchet@...s.st.com>,
        Mauro Carvalho Chehab
	<mchehab@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        "Alexandre
 Torgue" <alexandre.torgue@...s.st.com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König
	<christian.koenig@....com>
CC: <linux-media@...r.kernel.org>, <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <linaro-mm-sig@...ts.linaro.org>,
        Alain Volmat <alain.volmat@...s.st.com>
Subject: [PATCH 02/12] media: stm32: dcmi: perform dmaengine_slave_config
 at probe

Perform the dma channel configuration at probe time right after
the channel allocation since this is fixed for the whole lifetime
of the driver.

Signed-off-by: Alain Volmat <alain.volmat@...s.st.com>
---
 drivers/media/platform/st/stm32/stm32-dcmi.c | 32 +++++++++++++---------------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/drivers/media/platform/st/stm32/stm32-dcmi.c b/drivers/media/platform/st/stm32/stm32-dcmi.c
index 07b67eb5b9dd..27b283474096 100644
--- a/drivers/media/platform/st/stm32/stm32-dcmi.c
+++ b/drivers/media/platform/st/stm32/stm32-dcmi.c
@@ -301,23 +301,6 @@ static int dcmi_start_dma(struct stm32_dcmi *dcmi,
 			  struct dcmi_buf *buf)
 {
 	struct dma_async_tx_descriptor *desc = NULL;
-	struct dma_slave_config config;
-	int ret;
-
-	memset(&config, 0, sizeof(config));
-
-	config.src_addr = (dma_addr_t)dcmi->res->start + DCMI_DR;
-	config.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
-	config.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
-	config.dst_maxburst = 4;
-
-	/* Configure DMA channel */
-	ret = dmaengine_slave_config(dcmi->dma_chan, &config);
-	if (ret < 0) {
-		dev_err(dcmi->dev, "%s: DMA channel config failed (%d)\n",
-			__func__, ret);
-		return ret;
-	}
 
 	/*
 	 * Avoid call of dmaengine_terminate_sync() between
@@ -1888,6 +1871,7 @@ static int dcmi_probe(struct platform_device *pdev)
 	struct vb2_queue *q;
 	struct dma_chan *chan;
 	struct dma_slave_caps caps;
+	struct dma_slave_config dma_config;
 	struct clk *mclk;
 	int ret = 0;
 
@@ -1954,6 +1938,19 @@ static int dcmi_probe(struct platform_device *pdev)
 	if (!ret && caps.max_sg_burst)
 		dcmi->dma_max_burst = caps.max_sg_burst	* DMA_SLAVE_BUSWIDTH_4_BYTES;
 
+	memset(&dma_config, 0, sizeof(dma_config));
+
+	dma_config.src_addr = (dma_addr_t)dcmi->res->start + DCMI_DR;
+	dma_config.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
+
+	/* Configure DMA channel */
+	ret = dmaengine_slave_config(chan, &dma_config);
+	if (ret < 0) {
+		dev_err(dcmi->dev, "%s: DMA channel config failed (%d)\n",
+			__func__, ret);
+		goto err_dma_slave_config;
+	}
+
 	spin_lock_init(&dcmi->irqlock);
 	mutex_init(&dcmi->lock);
 	mutex_init(&dcmi->dma_lock);
@@ -2072,6 +2069,7 @@ static int dcmi_probe(struct platform_device *pdev)
 	v4l2_device_unregister(&dcmi->v4l2_dev);
 err_media_device_cleanup:
 	media_device_cleanup(&dcmi->mdev);
+err_dma_slave_config:
 	dma_release_channel(dcmi->dma_chan);
 
 	return ret;

-- 
2.34.1