Re: [PATCH 01/17] dmaengine: dw-edma: Fix residue burst index in tx_status()

[Frank Li]

On Tue, Jun 16, 2026 at 12:40:55AM +0900, Koichiro Den wrote:
> dw_edma_device_tx_status() uses desc->done_burst to subtract the
> completed byte count from the descriptor size. done_burst is a count of
> completed bursts, not the zero-based index of the last completed burst.
>
> Index desc->burst[] with done_burst - 1. Otherwise tx_status() reads the
> next burst's cumulative transfer size, which under-reports the residue
> and can become a one-past-the-end access when all bursts have completed.
>
> While at it, return early when txstate is NULL and drop the redundant
> desc check after vd2dw_edma_desc(). These are minor clean-ups since
> dma_set_residue() already tolerates a NULL state, and vd2dw_edma_desc()
> is only reached for a valid vdesc.
>
> Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
> ---
> @Frank, if you plan to respin 20260109-edma_ll-v2-0-5c0b27b2c664@xxxxxxx
> and agree with this patch, consider folding this fix into your patch
> when submitting your v3.

Okay, after config and prep pick, I will squash this into above one

Frank
>
>  drivers/dma/dw-edma/dw-edma-core.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
> index 1c8aef5e03b0..d99b6256660a 100644
> --- a/drivers/dma/dw-edma/dw-edma-core.c
> +++ b/drivers/dma/dw-edma/dw-edma-core.c
> @@ -244,7 +244,7 @@ dw_edma_device_tx_status(struct dma_chan *dchan, dma_cookie_t cookie,
>  		ret = DMA_PAUSED;
>
>  	if (!txstate)
> -		goto ret_residue;
> +		return ret;
>
>  	spin_lock_irqsave(&chan->vc.lock, flags);
>  	vd = vchan_find_desc(&chan->vc, cookie);
> @@ -252,12 +252,11 @@ dw_edma_device_tx_status(struct dma_chan *dchan, dma_cookie_t cookie,
>  		desc = vd2dw_edma_desc(vd);
>
>  		residue = desc->alloc_sz;
> -		if (desc && desc->done_burst)
> -			residue -= desc->burst[desc->done_burst].xfer_sz;
> +		if (desc->done_burst)
> +			residue -= desc->burst[desc->done_burst - 1].xfer_sz;
>  	}
>  	spin_unlock_irqrestore(&chan->vc.lock, flags);
>
> -ret_residue:
>  	dma_set_residue(txstate, residue);
>
>  	return ret;
> --
> 2.51.0
>