Re: [PATCH v5 2/2] dmaengine: dw-edma: Add changes to support Channel Separation

On 20-Aug-26 20:52, Frank Li wrote:
> On Thu, Aug 20, 2026 at 02:40:25PM +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 <[email protected]>
>> Reviewed-by: Frank Li <[email protected]>
>> ---
> 
> If only add my review-by, needn't post it new version. b4 will auto
> collect tags. I have to mark patch work status twices.
> 
> Frank
> 

Thank you for the suggestion.

-Devendra

>> Changes in v4:
>>     o No change.
>>
>> Changes in v3:
>>     o No change.
>>
>> 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 f287879b2cb9..2eb8293b87b4 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
>>