linux-kernel - [PATCH] dmaengine: at_xdmac: get the number of DMA channels from device tree

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Message-ID: <20251203120856.1267671-1-robert.marko@sartura.hr>
Date: Wed,  3 Dec 2025 13:08:23 +0100
From: Robert Marko <robert.marko@...tura.hr>
To: ludovic.desroches@...rochip.com,
	vkoul@...nel.org,
	linux-arm-kernel@...ts.infradead.org,
	dmaengine@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	daniel.machon@...rochip.com
Cc: luka.perkov@...tura.hr,
	Tony Han <tony.han@...rochip.com>,
	Cristian Birsan <cristian.birsan@...rochip.com>
Subject: [PATCH] dmaengine: at_xdmac: get the number of DMA channels from device tree

From: Tony Han <tony.han@...rochip.com>

In case of kernel runs in non-secure mode, the number of DMA channels can
be got from device tree since the value read from GTYPE register is "0" as
it's always secured.
As the number of channels can never be negative, update them to the type
"unsigned".

Signed-off-by: Tony Han <tony.han@...rochip.com>
Reviewed-by: Cristian Birsan <cristian.birsan@...rochip.com>
---
 drivers/dma/at_xdmac.c | 26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
index 3fbc74710a13..acabf82e293c 100644
--- a/drivers/dma/at_xdmac.c
+++ b/drivers/dma/at_xdmac.c
@@ -2257,12 +2257,29 @@ static int __maybe_unused atmel_xdmac_runtime_resume(struct device *dev)
 	return clk_enable(atxdmac->clk);
 }
 
+static inline int at_xdmac_get_channel_number(struct platform_device *pdev,
+					      u32 reg, u32 *pchannels)
+{
+	int	ret;
+
+	if (reg) {
+		*pchannels = AT_XDMAC_NB_CH(reg);
+		return 0;
+	}
+
+	ret = of_property_read_u32(pdev->dev.of_node, "dma-channels", pchannels);
+	if (ret)
+		dev_err(&pdev->dev, "can't get number of channels\n");
+
+	return ret;
+}
+
 static int at_xdmac_probe(struct platform_device *pdev)
 {
 	struct at_xdmac	*atxdmac;
-	int		irq, nr_channels, i, ret;
+	int		irq, ret;
 	void __iomem	*base;
-	u32		reg;
+	u32		nr_channels, i, reg;
 
 	irq = platform_get_irq(pdev, 0);
 	if (irq < 0)
@@ -2278,7 +2295,10 @@ static int at_xdmac_probe(struct platform_device *pdev)
 	 * of channels to do the allocation.
 	 */
 	reg = readl_relaxed(base + AT_XDMAC_GTYPE);
-	nr_channels = AT_XDMAC_NB_CH(reg);
+	ret = at_xdmac_get_channel_number(pdev, reg, &nr_channels);
+	if (ret)
+		return ret;
+
 	if (nr_channels > AT_XDMAC_MAX_CHAN) {
 		dev_err(&pdev->dev, "invalid number of channels (%u)\n",
 			nr_channels);
-- 
2.52.0