Re: [PATCH] iio: adc: nxp-sar-adc: Fix DMA channel leak in trigger mode

[Jonathan Cameron <jic23@kernel.org>]

On Sun, 22 Feb 2026 17:45:39 +0800
Felix Gu <ustc.gu@gmail.com> wrote:

> The DMA channel was requested in nxp_sar_adc_buffer_postenable() but
> was only released in nxp_sar_adc_buffer_software_do_predisable().
> This caused a DMA channel resource leak when operating in trigger mode.
> 
> Fix this by moving dma_request_chan() from
> nxp_sar_adc_buffer_postenable() into
> nxp_sar_adc_buffer_software_do_postenable(), ensuring the DMA channel
> is only requested in software mode.
> 
> Fixes: 4434072a893e ("iio: adc: Add the NXP SAR ADC support for the s32g2/3 platforms")
> Signed-off-by: Felix Gu <ustc.gu@gmail.com>

Hi Felix,

Just a trivial comment from me inline.  If that's all that comes up
I can make that changes when I apply it.

I'm looking for Daniel and maybe one or two others to take a look
at this before I pick it up.

Thanks,

Jonathan


> ---
>  drivers/iio/adc/nxp-sar-adc.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iio/adc/nxp-sar-adc.c b/drivers/iio/adc/nxp-sar-adc.c
> index 9efa883c277d..890c8ef3132f 100644
> --- a/drivers/iio/adc/nxp-sar-adc.c
> +++ b/drivers/iio/adc/nxp-sar-adc.c
> @@ -718,6 +718,10 @@ static int nxp_sar_adc_buffer_software_do_postenable(struct iio_dev *indio_dev)
>  	struct nxp_sar_adc *info = iio_priv(indio_dev);
>  	int ret;
>  
> +	info->dma_chan = dma_request_chan(indio_dev->dev.parent, "rx");
> +	if (IS_ERR(info->dma_chan))
> +		return PTR_ERR(info->dma_chan);
> +
>  	nxp_sar_adc_dma_channels_enable(info, *indio_dev->active_scan_mask);
>  
>  	nxp_sar_adc_dma_cfg(info, true);
> @@ -738,7 +742,7 @@ static int nxp_sar_adc_buffer_software_do_postenable(struct iio_dev *indio_dev)
>  out_dma_channels_disable:
>  	nxp_sar_adc_dma_cfg(info, false);
>  	nxp_sar_adc_dma_channels_disable(info, *indio_dev->active_scan_mask);
> -
> +	dma_release_channel(info->dma_chan);

Keep the blank line.  Having one just before a 'bare' return like this can help readability
a little so is common practice.

>  	return ret;
>  }
>  
> @@ -765,10 +769,6 @@ static int nxp_sar_adc_buffer_postenable(struct iio_dev *indio_dev)
>  	unsigned long channel;
>  	int ret;
>  
> -	info->dma_chan = dma_request_chan(indio_dev->dev.parent, "rx");
> -	if (IS_ERR(info->dma_chan))
> -		return PTR_ERR(info->dma_chan);
> -
>  	info->channels_used = 0;
>  
>  	/*
> 
> ---
> base-commit: d4906ae14a5f136ceb671bb14cedbf13fa560da6
> change-id: 20260222-nxp-sar-adc-1-bca71f089bc8
> 
> Best regards,