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

Frank Li
2026-01-16T15:45:33Z

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@gmail.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@synopsys.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
>