linux-kernel - Re: [PATCH] dmaengine: stm32-dma: set dma_device max_sg

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Message-ID: <20220117092516.GA431169@gnbcxd0016.gnb.st.com>
Date:   Mon, 17 Jan 2022 10:25:16 +0100
From:   Alain Volmat <alain.volmat@...s.st.com>
To:     Amelie Delaunay <amelie.delaunay@...s.st.com>
CC:     Vinod Koul <vkoul@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        <dmaengine@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dmaengine: stm32-dma: set dma_device max_sg_burst

Hi,

thanks Amelie.

Tested-by: Alain Volmat <alain.volmat@...s.st.com>

Alain

On Mon, Jan 17, 2022 at 10:17:40AM +0100, Amelie Delaunay wrote:
> Some stm32-dma consumers [1] rather use dma_get_slave_caps() to get
> max_sg_burst of their DMA channel as dma_get_max_seg_size() is specific to
> the DMA controller.
> All stm32-dma channels have the same features so, don't need to implement
> device_caps ops. Let dma_get_slave_caps() relies on dma_device
> configuration.
> That's why this patch sets dma_device max_sg_burst to the maximum segment
> size, which is the maximum of data items that can be transferred without
> software intervention.
> 
> [1] https://lore.kernel.org/lkml/20220110103739.118426-1-alain.volmat@foss.st.com/
>     "media: stm32: dcmi: create a dma scatterlist based on DMA max_sg_burst value"
> 
> Signed-off-by: Amelie Delaunay <amelie.delaunay@...s.st.com>
> ---
>  drivers/dma/stm32-dma.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/dma/stm32-dma.c b/drivers/dma/stm32-dma.c
> index 83a37a6955a3..d2365fab1b7a 100644
> --- a/drivers/dma/stm32-dma.c
> +++ b/drivers/dma/stm32-dma.c
> @@ -1389,6 +1389,7 @@ static int stm32_dma_probe(struct platform_device *pdev)
>  	dd->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
>  	dd->copy_align = DMAENGINE_ALIGN_32_BYTES;
>  	dd->max_burst = STM32_DMA_MAX_BURST;
> +	dd->max_sg_burst = STM32_DMA_ALIGNED_MAX_DATA_ITEMS;
>  	dd->descriptor_reuse = true;
>  	dd->dev = &pdev->dev;
>  	INIT_LIST_HEAD(&dd->channels);
> -- 
> 2.25.1
>