dmaengine: at_xdmac: get the number of DMA channels from device tree

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".

This is required for LAN969x.

Signed-off-by: Tony Han <tony.han@microchip.com>
Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Link: https://patch.msgid.link/20251203121208.1269487-1-robert.marko@sartura.hr
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Author: TonyHan11

drivers/dma/at_xdmac.c

@@ -2247,12 +2247,29 @@ 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)
@@ -2268,7 +2285,10 @@ 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);