Re: [PATCH v3 2/2] dmaengine: dw-edma: Add changes to support Channel Separation

[Frank Li <Frank.li@oss.nxp.com>]

On Mon, Aug 10, 2026 at 03:40:02PM +0530, Devendra K Verma wrote:
> HDMA supports configurable DMA channel register space
> separation which ranges from 256B to 32KB. Current implementation
> supports 256B as default for DMA channel register space.
> CPM6 supports the selection of channel register space via VSEC.
> The default value for channel register space for CPM6 is 512B.
>
> Updated the functions and methods to calculate the DMA channel
> registers base address as per the selected channel separation
> available as part of 'ch_space_sz'. Removed the unused function
> __dw_regs() and structs, namely dw_hdma_v0_ch and dw_hdma_v0_regs.
>
> Signed-off-by: Devendra K Verma <devverma@amd.com>
> ---

Reviewed-by: Frank Li <Frank.Li@nxp.com>

> Changes in v2:
>    o Replace 'ch_sep_sz' with 'ch_space_sz' as per review
>      recommendations.
>    o As patch 1/3 of previous series dropped after review,
>      this patch becomes 2/2 of the current series.
>
> Changes in v1:
>    o Updated the description as per the review comment
>    o Updated ch_sep_sz for EPC driver.
> ---
>  drivers/dma/dw-edma/dw-edma-pcie.c           |  4 ++++
>  drivers/dma/dw-edma/dw-hdma-v0-core.c        | 23 ++++++++++++--------
>  drivers/dma/dw-edma/dw-hdma-v0-debugfs.c     | 17 +++++----------
>  drivers/dma/dw-edma/dw-hdma-v0-regs.h        | 10 ---------
>  drivers/pci/controller/dwc/pcie-designware.c |  1 +
>  include/linux/dma/edma.h                     |  1 +
>  6 files changed, 26 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/dma/dw-edma/dw-edma-pcie.c b/drivers/dma/dw-edma/dw-edma-pcie.c
> index 5d7507a64056..81401620988c 100644
> --- a/drivers/dma/dw-edma/dw-edma-pcie.c
> +++ b/drivers/dma/dw-edma/dw-edma-pcie.c
> @@ -114,6 +114,7 @@ static const struct dw_edma_pcie_data snps_edda_data = {
>  	.irqs				= 1,
>  	.wr_ch_cnt			= 2,
>  	.rd_ch_cnt			= 2,
> +	.ch_space_sz			= 256,
>  };
>
>  static const struct dw_edma_pcie_data xilinx_mdb_data = {
> @@ -127,6 +128,7 @@ static const struct dw_edma_pcie_data xilinx_mdb_data = {
>  	.irqs				= 1,
>  	.wr_ch_cnt			= 8,
>  	.rd_ch_cnt			= 8,
> +	.ch_space_sz			= 256,
>  };
>
>  static const struct dw_edma_pcie_data xilinx_cpm6_dma_data = {
> @@ -140,6 +142,7 @@ static const struct dw_edma_pcie_data xilinx_cpm6_dma_data = {
>  	.irqs				= 1,
>  	.wr_ch_cnt			= 8,
>  	.rd_ch_cnt			= 8,
> +	.ch_space_sz			= 512,
>  };
>
>  static void dw_edma_set_chan_region_offset(struct dw_edma_pcie_data *pdata,
> @@ -436,6 +439,7 @@ static int dw_edma_pcie_probe(struct pci_dev *pdev,
>  	chip->nr_irqs = nr_irqs;
>  	chip->ops = &dw_edma_pcie_plat_ops;
>  	chip->cfg_non_ll = non_ll;
> +	chip->ch_space_sz = vsec_data->ch_space_sz;
>
>  	chip->ll_wr_cnt = vsec_data->wr_ch_cnt;
>  	chip->ll_rd_cnt = vsec_data->rd_ch_cnt;
> diff --git a/drivers/dma/dw-edma/dw-hdma-v0-core.c b/drivers/dma/dw-edma/dw-hdma-v0-core.c
> index 632abb8b481c..f8b2383b294a 100644
> --- a/drivers/dma/dw-edma/dw-hdma-v0-core.c
> +++ b/drivers/dma/dw-edma/dw-hdma-v0-core.c
> @@ -23,18 +23,23 @@ enum dw_hdma_control {
>  	DW_HDMA_V0_LLE					= BIT(9),
>  };
>
> -static inline struct dw_hdma_v0_regs __iomem *__dw_regs(struct dw_edma *dw)
> -{
> -	return dw->chip->reg_base;
> -}
> -
>  static inline struct dw_hdma_v0_ch_regs __iomem *
>  __dw_ch_regs(struct dw_edma *dw, enum dw_edma_dir dir, u16 ch)
>  {
> -	if (dir == EDMA_DIR_WRITE)
> -		return &(__dw_regs(dw)->ch[ch].wr);
> -	else
> -		return &(__dw_regs(dw)->ch[ch].rd);
> +	u32 ch_base;
> +
> +	/*
> +	 * For Write, the channel register index starts at
> +	 * wr_base(ch_idx) = (2 * ch_idx) * ch_space_sz
> +	 *
> +	 * For Read channel,
> +	 * rd_base(ch_idx) = (2 * ch_idx + 1) * ch_space_sz
> +	 */
> +	ch_base = 2 * ch;
> +	if (dir == EDMA_DIR_READ)
> +		ch_base += 1;
> +
> +	return dw->chip->reg_base + (ch_base * dw->chip->ch_space_sz);
>  }
>
>  #define SET_CH_32(dw, dir, ch, name, value) \
> diff --git a/drivers/dma/dw-edma/dw-hdma-v0-debugfs.c b/drivers/dma/dw-edma/dw-hdma-v0-debugfs.c
> index dcdc57fe976c..3fa16e045a58 100644
> --- a/drivers/dma/dw-edma/dw-hdma-v0-debugfs.c
> +++ b/drivers/dma/dw-edma/dw-hdma-v0-debugfs.c
> @@ -13,22 +13,17 @@
>  #include "dw-hdma-v0-regs.h"
>  #include "dw-edma-core.h"
>
> -#define REGS_ADDR(dw, name)						       \
> -	({								       \
> -		struct dw_hdma_v0_regs __iomem *__regs = (dw)->chip->reg_base; \
> -									       \
> -		(void __iomem *)&__regs->name;				       \
> -	})
> -
>  #define REGS_CH_ADDR(dw, name, _dir, _ch)				       \
>  	({								       \
> -		struct dw_hdma_v0_ch_regs __iomem *__ch_regs;		       \
> +		struct dw_hdma_v0_ch_regs __iomem *__ch_regs;                  \
> +		off_t __off = (dw)->chip->ch_space_sz;			       \
>  									       \
> -		if (_dir == EDMA_DIR_READ)				       \
> -			__ch_regs = REGS_ADDR(dw, ch[_ch].rd);		       \
> +		if ((_dir) == EDMA_DIR_READ)				       \
> +			__off *= (2 * (_ch) + 1);			       \
>  		else							       \
> -			__ch_regs = REGS_ADDR(dw, ch[_ch].wr);		       \
> +			__off *= (2 * (_ch));				       \
>  									       \
> +		__ch_regs = ((dw)->chip->reg_base + __off);		       \
>  		(void __iomem *)&__ch_regs->name;			       \
>  	})
>
> diff --git a/drivers/dma/dw-edma/dw-hdma-v0-regs.h b/drivers/dma/dw-edma/dw-hdma-v0-regs.h
> index 7759ba9b4850..2475b8d96133 100644
> --- a/drivers/dma/dw-edma/dw-hdma-v0-regs.h
> +++ b/drivers/dma/dw-edma/dw-hdma-v0-regs.h
> @@ -84,16 +84,6 @@ struct dw_hdma_v0_ch_regs {
>  		};
>  	} msi_abort;
>  	u32 msi_msgdata;			/* 0x00a8 */
> -	u32 padding_2[21];			/* 0x00ac..0x00fc */
> -} __packed;
> -
> -struct dw_hdma_v0_ch {
> -	struct dw_hdma_v0_ch_regs wr;		/* 0x0000 */
> -	struct dw_hdma_v0_ch_regs rd;		/* 0x0100 */
> -} __packed;
> -
> -struct dw_hdma_v0_regs {
> -	struct dw_hdma_v0_ch ch[HDMA_V0_MAX_NR_CH];	/* 0x0000..0x0fa8 */
>  } __packed;
>
>  struct dw_hdma_v0_lli {
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index ec4722ed9303..dfb7deaff751 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -1049,6 +1049,7 @@ static void dw_pcie_edma_init_data(struct dw_pcie *pci)
>  		pci->edma.ops = &dw_pcie_edma_ops;
>
>  	pci->edma.flags |= DW_EDMA_CHIP_LOCAL;
> +	pci->edma.ch_space_sz = 256;
>  }
>
>  static int dw_pcie_edma_find_mf(struct dw_pcie *pci)
> diff --git a/include/linux/dma/edma.h b/include/linux/dma/edma.h
> index 1fafd5b0e315..182d4eeae22a 100644
> --- a/include/linux/dma/edma.h
> +++ b/include/linux/dma/edma.h
> @@ -104,6 +104,7 @@ struct dw_edma_chip {
>
>  	struct dw_edma		*dw;
>  	bool			cfg_non_ll;
> +	u32			ch_space_sz;
>  };
>
>  /* Export to the platform drivers */
> --
> 2.43.0
>