linux-kernel - [PATCH 1/2] dmaengine: at_xdmac: get the number of DMA channels from device tree

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Message-ID: <20250205-mchp-dma-v1-1-124b639d5afe@microchip.com>
Date: Wed, 5 Feb 2025 11:17:02 +0530
From: Dharma Balasubiramani <dharma.b@...rochip.com>
To: Ludovic Desroches <ludovic.desroches@...rochip.com>, Vinod Koul
	<vkoul@...nel.org>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski
	<krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Nicolas Ferre
	<nicolas.ferre@...rochip.com>, Alexandre Belloni
	<alexandre.belloni@...tlin.com>, Claudiu Beznea <claudiu.beznea@...on.dev>,
	Charan Pedumuru <charan.pedumuru@...rochip.com>
CC: <linux-arm-kernel@...ts.infradead.org>, <dmaengine@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>, "Dharma
 Balasubiramani" <dharma.b@...rochip.com>, Tony Han <tony.han@...rochip.com>,
	Cristian Birsan <cristian.birsan@...rochip.com>
Subject: [PATCH 1/2] 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 ba25c23164e7..f777b0665c63 100644
--- a/drivers/dma/at_xdmac.c
+++ b/drivers/dma/at_xdmac.c
@@ -2259,12 +2259,29 @@ 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)
@@ -2280,7 +2297,10 @@ 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);

-- 
2.43.0