linux-kernel - Re: [PATCH v2 2/3] dmaengine: dw-axi-dmac: Add support for CV1800B DMA

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Message-ID: <aWpdEKVBjbq7Lrqv@lizhi-Precision-Tower-5810>
Date: Fri, 16 Jan 2026 10:45:20 -0500
From: Frank Li <Frank.li@....com>
To: Inochi Amaoto <inochiama@...il.com>
Cc: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
	Vinod Koul <vkoul@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Paul Walmsley <pjw@...nel.org>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>,
	Chen Wang <unicorn_wang@...look.com>,
	Alexander Sverdlin <alexander.sverdlin@...il.com>,
	Longbin Li <looong.bin@...il.com>, Ze Huang <huangze@...t.edu.cn>,
	"Anton D . Stavinskii" <stavinsky@...il.com>,
	dmaengine@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
	sophgo@...ts.linux.dev, Yixun Lan <dlan@...too.org>
Subject: Re: [PATCH v2 2/3] dmaengine: dw-axi-dmac: Add support for CV1800B
 DMA

On Mon, Dec 15, 2025 at 06:45:59AM +0800, 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 controls the DMA interrupt multiplexer, which
> 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@...il.com>
> ---
>  .../dma/dw-axi-dmac/dw-axi-dmac-platform.c    | 26 ++++++++++++++++---
>  drivers/dma/dw-axi-dmac/dw-axi-dmac.h         |  1 +
>  2 files changed, 23 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 b23536645ff7..829aa6c05b5c 100644
> --- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> +++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> @@ -7,6 +7,7 @@
>   * Author: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
>   */
>
> +#include "linux/stddef.h"
>  #include <linux/bitops.h>
>  #include <linux/delay.h>
>  #include <linux/device.h>
> @@ -50,6 +51,7 @@
>  #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)

Look like ARG0_AS_CHAN is easy understand

Frank
>
>  static inline void
>  axi_dma_iowrite32(struct axi_dma_chip *chip, u32 reg, u32 val)
> @@ -1360,16 +1362,27 @@ static int __maybe_unused axi_dma_runtime_resume(struct device *dev)
>  static struct dma_chan *dw_axi_dma_of_xlate(struct of_phandle_args *dma_spec,
>  					    struct of_dma *ofdma)
>  {
> +	unsigned int handshake = dma_spec->args[0];
>  	struct dw_axi_dma *dw = ofdma->of_dma_data;
> -	struct axi_dma_chan *chan;
> +	struct axi_dma_chan *chan = NULL;
>  	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)
> +		chan = dchan_to_axi_dma_chan(dchan);
> +	chan->hw_handshake_num = handshake;
>  	return dchan;
>  }
>
> @@ -1508,6 +1521,8 @@ 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 +1678,9 @@ 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
>