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

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Message-ID: <aUF4OS4DsmRlQQt3@vaman>
Date: Tue, 16 Dec 2025 20:48:17 +0530
From: Vinod Koul <vkoul@...nel.org>
To: Robert Marko <robert.marko@...tura.hr>
Cc: ludovic.desroches@...rochip.com, linux-arm-kernel@...ts.infradead.org,
	dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
	daniel.machon@...rochip.com, luka.perkov@...tura.hr,
	Tony Han <tony.han@...rochip.com>
Subject: Re: [PATCH RESEND] dmaengine: at_xdmac: get the number of DMA
 channels from device tree

On 03-12-25, 13:11, Robert Marko wrote:
> 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".
> 
> This is required for LAN969x.

You updated the changelog, but tagged it as resend. It should be v2!

> 
> Signed-off-by: Tony Han <tony.han@...rochip.com>
> Signed-off-by: Robert Marko <robert.marko@...tura.hr>
> ---
>  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");

Do we need to log error, I thought the API did that...

> +
> +	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

-- 
~Vinod