linux-kernel - Re: [PATCH 4/7] dma: mcf-edma: Fix interrupt handler for 64 DMA channels

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Message-ID: <aSSDItseEjQ0VMh6@lizhi-Precision-Tower-5810>
Date: Mon, 24 Nov 2025 11:09:06 -0500
From: Frank Li <Frank.li@....com>
To: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
Cc: Vinod Koul <vkoul@...nel.org>, Greg Ungerer <gerg@...ux-m68k.org>,
	imx@...ts.linux.dev, dmaengine@...r.kernel.org,
	linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/7] dma: mcf-edma: Fix interrupt handler for 64 DMA
 channels

On Mon, Nov 24, 2025 at 01:50:25PM +0100, Jean-Michel Hautbois wrote:
> Fix the DMA completion interrupt handler to properly handle all 64
> channels on MCF54418 ColdFire processors.
>
> The previous code used BIT(ch) to test interrupt status bits, which
> causes undefined behavior on 32-bit architectures when ch >= 32 because
> unsigned long is 32 bits and the shift would exceed the type width.
>
> Replace with bitmap_from_u64() and for_each_set_bit() which correctly
> handle 64-bit values on 32-bit systems by using a proper bitmap
> representation.
>
> Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
> ---
>  drivers/dma/mcf-edma-main.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/dma/mcf-edma-main.c b/drivers/dma/mcf-edma-main.c
> index 8a7c1787adb1f66f3b6729903635b072218afad1..dd64f50f2b0a70a4664b03c7d6a23e74c9bcd7ae 100644
> --- a/drivers/dma/mcf-edma-main.c
> +++ b/drivers/dma/mcf-edma-main.c
> @@ -18,7 +18,8 @@ static irqreturn_t mcf_edma_tx_handler(int irq, void *dev_id)
>  {
>  	struct fsl_edma_engine *mcf_edma = dev_id;
>  	struct edma_regs *regs = &mcf_edma->regs;
> -	unsigned int ch;
> +	unsigned long ch;

channel number max value is 63. unsigned int should be enough.

Frank
> +	DECLARE_BITMAP(status_mask, 64);
>  	u64 intmap;
>
>  	intmap = ioread32(regs->inth);
> @@ -27,11 +28,11 @@ static irqreturn_t mcf_edma_tx_handler(int irq, void *dev_id)
>  	if (!intmap)
>  		return IRQ_NONE;
>
> -	for (ch = 0; ch < mcf_edma->n_chans; ch++) {
> -		if (intmap & BIT(ch)) {
> -			iowrite8(EDMA_MASK_CH(ch), regs->cint);
> -			fsl_edma_tx_chan_handler(&mcf_edma->chans[ch]);
> -		}
> +	bitmap_from_u64(status_mask, intmap);
> +
> +	for_each_set_bit(ch, status_mask, mcf_edma->n_chans) {
> +		iowrite8(EDMA_MASK_CH(ch), regs->cint);
> +		fsl_edma_tx_chan_handler(&mcf_edma->chans[ch]);
>  	}
>
>  	return IRQ_HANDLED;
>
> --
> 2.39.5
>