linux-kernel - Re: [PATCH 07/25] dmaengine: dw-edma: Don't permit non-inc interleaved xfers

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Date:   Thu, 24 Mar 2022 22:45:12 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Vinod Koul <vkoul@...nel.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Frank Li <Frank.Li@....com>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        linux-pci@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/25] dmaengine: dw-edma: Don't permit non-inc
 interleaved xfers

On Thu, Mar 24, 2022 at 04:48:18AM +0300, Serge Semin wrote:
> DW eDMA controller always increments both source and destination
> addresses. Permitting DMA interleaved transfers with no src_inc/dst_inc
> flags set may lead to unexpected behaviour for the device users. Let's fix
> that by terminating the interleaved transfers if at least one of the
> dma_interleaved_template.{src_inc,dst_inc} flag is initialized with false
> value. Note in addition to that we need we need to increase the source and
> destination addresses accordingly after each iteration.
> 

Can you please point me where this gets documented in databook?

Thanks,
Mani

> Fixes: 85e7518f42c8 ("dmaengine: dw-edma: Add device_prep_interleave_dma() support")
> Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> ---
>  drivers/dma/dw-edma/dw-edma-core.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
> index 2010d7f8191f..f41bde27795c 100644
> --- a/drivers/dma/dw-edma/dw-edma-core.c
> +++ b/drivers/dma/dw-edma/dw-edma-core.c
> @@ -386,6 +386,8 @@ dw_edma_device_transfer(struct dw_edma_transfer *xfer)
>  			return NULL;
>  		if (xfer->xfer.il->numf > 0 && xfer->xfer.il->frame_size > 0)
>  			return NULL;
> +		if (!xfer->xfer.il->src_inc || !xfer->xfer.il->dst_inc)
> +			return NULL;
>  	} else {
>  		return NULL;
>  	}
> @@ -485,15 +487,13 @@ dw_edma_device_transfer(struct dw_edma_transfer *xfer)
>  			struct dma_interleaved_template *il = xfer->xfer.il;
>  			struct data_chunk *dc = &il->sgl[i];
>  
> -			if (il->src_sgl) {
> -				src_addr += burst->sz;
> +			src_addr += burst->sz;
> +			if (il->src_sgl)
>  				src_addr += dmaengine_get_src_icg(il, dc);
> -			}
>  
> -			if (il->dst_sgl) {
> -				dst_addr += burst->sz;
> +			dst_addr += burst->sz;
> +			if (il->dst_sgl)
>  				dst_addr += dmaengine_get_dst_icg(il, dc);
> -			}
>  		}
>  	}
>  
> -- 
> 2.35.1
>