Re: [PATCH 3/3] dmaengine: dw-axi-dmac: Decode errors in the transfer failure log

[Frank Li]

On Tue, Oct 06, 2026 at 01:03:09AM +0000, Roland Dreier wrote:
> axi_chan_handle_err() reports every error with "Bad descriptor
> submitted" and dumps the transfer's LLIs. Common errors are source and
> destination decode or slave errors, from an undecoded address or a
> target returning an error response. These errors do not necessarily
> indicate a malformed descriptor, so the message is misleading. The
> dump also has one line per LLI without any indication where the
> transfer failed.
>
> Report the first matching error name while retaining the raw interrupt
> status so additional error bits remain visible. Include SAR, DAR and
> LLP to provide hardware progress and linked-list context without
> dumping every LLI. These registers are diagnostic snapshots, not
> necessarily the exact addresses of the failing transactions.
>
> Dump the LLIs only when a descriptor or programming error is present.
> Leave the transfer result and recovery path unchanged.
>
> Assisted-by: LLM
> Signed-off-by: Roland Dreier <rolanddreier@xxxxxxxxxx>
> ---

Reviewed-by: Frank Li <Frank.Li@xxxxxxx>

>  drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c | 46 +++++++++++++++++++++++---
>  1 file changed, 42 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> index 88362f181207..e5a259e79a38 100644
> --- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> +++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> @@ -1059,6 +1059,36 @@ static void axi_chan_list_dump_lli(struct axi_dma_chan *chan,
>  		axi_chan_dump_lli(chan, &desc_head->hw_desc[i]);
>  }
>
> +#define AXI_DMA_DATA_ERR	(DWAXIDMAC_IRQ_SRC_DEC_ERR | \
> +			 DWAXIDMAC_IRQ_SRC_SLV_ERR | \
> +			 DWAXIDMAC_IRQ_DST_DEC_ERR | \
> +			 DWAXIDMAC_IRQ_DST_SLV_ERR)
> +
> +static const char *axi_chan_err_str(u32 status)
> +{
> +	if (status & DWAXIDMAC_IRQ_SRC_DEC_ERR)
> +		return "source decode error";
> +	if (status & DWAXIDMAC_IRQ_SRC_SLV_ERR)
> +		return "source slave error";
> +	if (status & DWAXIDMAC_IRQ_DST_DEC_ERR)
> +		return "destination decode error";
> +	if (status & DWAXIDMAC_IRQ_DST_SLV_ERR)
> +		return "destination slave error";
> +	if (status & DWAXIDMAC_IRQ_LLI_RD_DEC_ERR)
> +		return "LLI read decode error";
> +	if (status & DWAXIDMAC_IRQ_LLI_RD_SLV_ERR)
> +		return "LLI read slave error";
> +	if (status & DWAXIDMAC_IRQ_LLI_WR_DEC_ERR)
> +		return "LLI write-back decode error";
> +	if (status & DWAXIDMAC_IRQ_LLI_WR_SLV_ERR)
> +		return "LLI write-back slave error";
> +	if (status & DWAXIDMAC_IRQ_INVALID_ERR)
> +		return "invalid LLI or shadow register";
> +	if (status & DWAXIDMAC_IRQ_MULTIBLKTYPE_ERR)
> +		return "invalid multi-block transfer type";
> +	return "slave interface error";
> +}
> +
>  static noinline void axi_chan_handle_err(struct axi_dma_chan *chan, u32 status)
>  {
>  	struct virt_dma_desc *vd;
> @@ -1078,11 +1108,19 @@ static noinline void axi_chan_handle_err(struct axi_dma_chan *chan, u32 status)
>  	/* Remove the completed descriptor from issued list */
>  	list_del(&vd->node);
>
> -	/* WARN about bad descriptor */
> +	/*
> +	 * SAR and DAR advance as each burst is issued, so with bursts still
> +	 * outstanding they can be a little past the one that failed.
> +	 */
>  	dev_err(chan2dev(chan),
> -		"Bad descriptor submitted for %s, cookie: %d, irq: 0x%08x\n",
> -		axi_chan_name(chan), vd->tx.cookie, status);
> -	axi_chan_list_dump_lli(chan, vd_to_axi_desc(vd));
> +		"%s for %s, cookie: %d, irq: 0x%08x, SAR: 0x%llx DAR: 0x%llx LLP: 0x%llx\n",
> +		axi_chan_err_str(status), axi_chan_name(chan), vd->tx.cookie,
> +		status, lo_hi_readq(chan->chan_regs + CH_SAR),
> +		lo_hi_readq(chan->chan_regs + CH_DAR),
> +		lo_hi_readq(chan->chan_regs + CH_LLP));
> +	/* Only dump LLIs on non-data errors */
> +	if (status & (DWAXIDMAC_IRQ_ALL_ERR & ~AXI_DMA_DATA_ERR))
> +		axi_chan_list_dump_lli(chan, vd_to_axi_desc(vd));
>
>  	if (status & (DWAXIDMAC_IRQ_SRC_DEC_ERR | DWAXIDMAC_IRQ_SRC_SLV_ERR))
>  		vd->tx_result.result = DMA_TRANS_READ_FAILED;
>
> --
> 2.54.0
>