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

[Jonathan Cameron <jic23@kernel.org>]

On Sun, 22 Feb 2026 16:08:57 +0000
Jonathan Cameron <jic23@kernel.org> wrote:

> 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.
> 
Long enough I think.

Applied to the fixes-togreg branch of iio.git and marked for stable.

Thanks,

Jonathan

> 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,  
> 
>