Re: [PATCH 2/3] dmaengine: dw-axi-dmac: Add support for CV1800B DMA

[Samuel Holland <samuel.holland@sifive.com>]

Hi Inochi,

On 2025-12-12 11:05 AM, Inochi Amaoto wrote:
> As the DMA controller on Sophgo CV1800 series SoC only has 8 channels,
> the SoC provides a dma multiplexer to reuse the DMA channel. However,
> the dma multiplexer also controlls the DMA interrupt multiplexer, which

typo: controls

> means that the dma multiplexer needs to know the channel number.
> 
> Allow the driver to use DMA phandle args as the channel number, so the
> DMA multiplexer can route the DMA interrupt correctly.
> 
> Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
> ---
>  .../dma/dw-axi-dmac/dw-axi-dmac-platform.c    | 23 ++++++++++++++++---
>  drivers/dma/dw-axi-dmac/dw-axi-dmac.h         |  1 +
>  2 files changed, 21 insertions(+), 3 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 b23536645ff7..62bf0d0dc354 100644
> --- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> +++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> @@ -50,6 +50,7 @@
>  #define AXI_DMA_FLAG_HAS_APB_REGS	BIT(0)
>  #define AXI_DMA_FLAG_HAS_RESETS		BIT(1)
>  #define AXI_DMA_FLAG_USE_CFG2		BIT(2)
> +#define AXI_DMA_FLAG_HANDSHAKE_AS_CHAN	BIT(3)
> 
>  static inline void
>  axi_dma_iowrite32(struct axi_dma_chip *chip, u32 reg, u32 val)
> @@ -1361,15 +1362,26 @@ static struct dma_chan *dw_axi_dma_of_xlate(struct of_phandle_args *dma_spec,
>  					    struct of_dma *ofdma)
>  {
>  	struct dw_axi_dma *dw = ofdma->of_dma_data;
> +	unsigned int handshake = dma_spec->args[0];
>  	struct axi_dma_chan *chan;
>  	struct dma_chan *dchan;
> 
> -	dchan = dma_get_any_slave_channel(&dw->dma);
> +	if (dw->hdata->use_handshake_as_channel_number) {
> +		if (handshake >= dw->hdata->nr_channels)
> +			return NULL;
> +
> +		chan = &dw->chan[handshake];
> +		dchan = dma_get_slave_channel(&chan->vc.chan);
> +	} else {
> +		dchan = dma_get_any_slave_channel(&dw->dma);
> +	}
> +
>  	if (!dchan)
>  		return NULL;
> 
> -	chan = dchan_to_axi_dma_chan(dchan);
> -	chan->hw_handshake_num = dma_spec->args[0];
> +	if (!chan)

When use_handshake_as_channel_number is false, chan is uninitialized here.

Regards,
Samuel

> +		chan = dchan_to_axi_dma_chan(dchan);
> +	chan->hw_handshake_num = handshake;
>  	return dchan;
>  }
> 
> @@ -1508,6 +1520,8 @@ static int dw_probe(struct platform_device *pdev)
>  			return ret;
>  	}
> 
> +	chip->dw->hdata->use_handshake_as_channel_number = !!(flags & AXI_DMA_FLAG_HANDSHAKE_AS_CHAN);
> +
>  	chip->dw->hdata->use_cfg2 = !!(flags & AXI_DMA_FLAG_USE_CFG2);
> 
>  	chip->core_clk = devm_clk_get(chip->dev, "core-clk");
> @@ -1663,6 +1677,9 @@ static const struct of_device_id dw_dma_of_id_table[] = {
>  	}, {
>  		.compatible = "intel,kmb-axi-dma",
>  		.data = (void *)AXI_DMA_FLAG_HAS_APB_REGS,
> +	}, {
> +		.compatible = "sophgo,cv1800b-axi-dma",
> +		.data = (void *)AXI_DMA_FLAG_HANDSHAKE_AS_CHAN,
>  	}, {
>  		.compatible = "starfive,jh7110-axi-dma",
>  		.data = (void *)(AXI_DMA_FLAG_HAS_RESETS | AXI_DMA_FLAG_USE_CFG2),
> diff --git a/drivers/dma/dw-axi-dmac/dw-axi-dmac.h b/drivers/dma/dw-axi-dmac/dw-axi-dmac.h
> index b842e6a8d90d..67cc199e24d1 100644
> --- a/drivers/dma/dw-axi-dmac/dw-axi-dmac.h
> +++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac.h
> @@ -34,6 +34,7 @@ struct dw_axi_dma_hcfg {
>  	bool	reg_map_8_channels;
>  	bool	restrict_axi_burst_len;
>  	bool	use_cfg2;
> +	bool	use_handshake_as_channel_number;
>  };
> 
>  struct axi_dma_chan {
> --
> 2.52.0
> 
> 
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