linux-kernel - Re: [PATCH v2 2/5] dma: mcf-edma: Add per-channel IRQ naming for debugging

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Message-ID: <5064909.31r3eYUQgx@jeanmichel-ms7b89>
Date: Wed, 17 Dec 2025 07:34:07 +0100
From: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
To: Vinod Koul <vkoul@...nel.org>, Frank Li <Frank.li@....com>,
 Greg Ungerer <gerg@...ux-m68k.org>
Cc: imx@...ts.linux.dev, dmaengine@...r.kernel.org,
 linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org
Subject:
 Re: [PATCH v2 2/5] dma: mcf-edma: Add per-channel IRQ naming for debugging

Hi Frank,

Le mardi 16 décembre 2025, 16:38:38 heure normale d’Europe centrale Frank Li a 
écrit :
> On Tue, Dec 16, 2025 at 08:56:01PM +0530, Vinod Koul wrote:
> > On 26-11-25, 11:12, Frank Li wrote:
> > > On Wed, Nov 26, 2025 at 09:36:03AM +0100, Jean-Michel Hautbois via B4 
Relay wrote:
> > > > From: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
> > > > 
> > > > Add dynamic per-channel IRQ naming to make DMA interrupt
> > > > identification
> > > > easier in /proc/interrupts and debugging tools.
> > > > 
> > > > Instead of all channels showing "eDMA", they now show:
> > > > - "eDMA-0" through "eDMA-15" for channels 0-15
> > > > - "eDMA-16" through "eDMA-55" for channels 16-55
> > > > - "eDMA-tx-56" for the shared channel 56-63 interrupt
> > > > - "eDMA-err" for the error interrupt
> > > > 
> > > > This aids debugging DMA issues by making it clear which channel's
> > > > interrupt is being serviced.
> > > > 
> > > > Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
> > > > ---
> > > > 
> > > >  drivers/dma/mcf-edma-main.c | 26 ++++++++++++++++++--------
> > > >  1 file changed, 18 insertions(+), 8 deletions(-)
> > > > 
> > > > diff --git a/drivers/dma/mcf-edma-main.c b/drivers/dma/mcf-edma-main.c
> > > > index f95114829d80..6a7d88895501 100644
> > > > --- a/drivers/dma/mcf-edma-main.c
> > > > +++ b/drivers/dma/mcf-edma-main.c
> > > > @@ -81,8 +81,14 @@ static int mcf_edma_irq_init(struct platform_device
> > > > *pdev,> > > 
> > > >  	if (!res)
> > > >  	
> > > >  		return -1;
> > > > 
> > > > -	for (ret = 0, i = res->start; i <= res->end; ++i)
> > > > -		ret |= request_irq(i, mcf_edma_tx_handler, 0, "eDMA", 
mcf_edma);
> > > > +	for (ret = 0, i = res->start; i <= res->end; ++i) {
> > > > +		char *irq_name = devm_kasprintf(&pdev->dev, 
GFP_KERNEL,
> > > > +						"eDMA-%d", 
(int)(i - res->start));
> > > > +		if (!irq_name)
> > > > +			return -ENOMEM;
> > > > +
> > > > +		ret |= request_irq(i, mcf_edma_tx_handler, 0, 
irq_name, mcf_edma);
> > > > +	}
> > > > 
> > > >  	if (ret)
> > > >  	
> > > >  		return ret;
> > > 
> > > The existing code have problem, it should use devm_request_irq(). if one
> > > irq request failure, return here,  requested irq will not free.
> > 
> > Why is that an error!
> 
>         ret = fsl_edma->drvdata->setup_irq(pdev, fsl_edma);
>         if (ret)
>                 return ret;
> 
> if last one of request_irq() failure, mcf_edma_irq_init() return failure.
> probe will return failure also without free irq.
> 
> So previous irq by request_irq() is never free at this case.

From kernel/irq/manage.c I see in a nutshell:
	request_threaded_irq() {
		action = kzalloc(sizeof(struct irqaction), GFP_KERNEL);
		retval = __setup_irq(irq, desc, action);
		if (retval) {
			kfree(action->secondary);
			kfree(action);
		}
	}

I don't see an issue with the existing code then ?
Am I wrong ?

Thanks,
JM

> 
> Frank
> 
> > > You'd better add patch before this one to change to use
> > > devm_request_irq()
> > 
> > Not really, devm_ is a not always good option.
> > 
> > --
> > ~Vinod