Re: [PATCH v1 3/3] dmaengine: dw-edma: Add changes to support Channel Separation

["Verma, Devendra" <devverma@amd.com>]

On 22-Jul-26 20:52, Frank Li wrote:
> On Wed, Jul 22, 2026 at 04:46:40PM +0530, Devendra K Verma wrote:
> 
> Add Koichiro Den, who did many work with this edma driver recently
> 

Sure, thanks!

>> Following changes are made:
>> o In 'struct dw_hdma_v0_ch_regs', it is assumed the channel
>>    separation as 256-bytes which is default, but if an IP is
> 
> channel register space size?
> 
>>    configured for a different size of channel separation then
>>    user can retrieve it using the supported VSEC (0x6).
>>    Modified the struct to work with the channel separation
>>    supported by IP.
>>    CPM6 supports channel separation, default is 512.
> 
> 
>> o Changes in macros / functions where address of the channel
>>    is accessed based on channel index and direction. It enables
>>    the calculation of the channel reg base address based on
>>    the selected channel separation.
>> o Struct removed - dw_hdma_v0_ch, dw_hdma_v0_regs
>> o Functions removed - __dw_regs()
> 
> Can you summary change and purpose? such as
> 
> Support difference channel register space size for difference IP. Previous
> use fix default value 256, CMP6 support difference register space size,
> which default value is 512.
> 
> Update channel register base address caluator method by use ch_space_sze
> and remove unused dw_hdma_v0_ch, dw_hdma_v0_regs.
> 
> You can rephrase.
> 

Sure, I will rephrase this. Thank you for the suggestion!

>>
>> Signed-off-by: Devendra K Verma <devverma@amd.com>
>> ---
>>   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 ----------
>>   include/linux/dma/edma.h                 |  1 +
>>   5 files changed, 25 insertions(+), 30 deletions(-)
>>
>> diff --git a/drivers/dma/dw-edma/dw-edma-pcie.c b/drivers/dma/dw-edma/dw-edma-pcie.c
>> index 6295d01ba2f7..ca2a4be2f3a5 100644
>> --- a/drivers/dma/dw-edma/dw-edma-pcie.c
>> +++ b/drivers/dma/dw-edma/dw-edma-pcie.c
>> @@ -113,6 +113,7 @@ static const struct dw_edma_pcie_data snps_edda_data = {
>>   	.irqs				= 1,
>>   	.wr_ch_cnt			= 2,
>>   	.rd_ch_cnt			= 2,
>> +	.ch_sep_sz			= 256,
>>   };
>>
>>   static const struct dw_edma_pcie_data xilinx_mdb_data = {
>> @@ -126,6 +127,7 @@ static const struct dw_edma_pcie_data xilinx_mdb_data = {
>>   	.irqs				= 1,
>>   	.wr_ch_cnt			= 8,
>>   	.rd_ch_cnt			= 8,
>> +	.ch_sep_sz			= 256,
>>   };
>>
>>   static const struct dw_edma_pcie_data xilinx_cpm6_dma_data = {
>> @@ -139,6 +141,7 @@ static const struct dw_edma_pcie_data xilinx_cpm6_dma_data = {
>>   	.irqs				= 1,
>>   	.wr_ch_cnt			= 8,
>>   	.rd_ch_cnt			= 8,
>> +	.ch_sep_sz			= 512,
>>   };
>>
>>   static void dw_edma_set_chan_region_offset(struct dw_edma_pcie_data *pdata,
>> @@ -443,6 +446,7 @@ 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_sep_sz = vsec_data->ch_sep_sz;
> 
> 
> This blocks PCI endpoint DMA, this driver is not only used by this.
> EPC controller will not set this value, so ch_sep_sz will be 0 for EPC
> controller.
> 
> Frank
> 

The EPC driver is using the chip->reg_base + reg_offset for computing
the final addresse and not using the register mappings. If the
reg_offset are correct then this ch_sep_sz change will not affect the
EPC driver.

>>
>>   	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..3f27a93c4d8c 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_sep_sz
>> +	 *
>> +	 * For Read channel,
>> +	 * rd_base(ch_idx) = (2 * ch_idx + 1) * ch_sep_sz
>> +	 */
>> +	ch_base = 2 * ch;
>> +	if (dir == EDMA_DIR_READ)
>> +		ch_base += 1;
>> +
>> +	return dw->chip->reg_base + (ch_base * dw->chip->ch_sep_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..33128685bbd9 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_sep_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/include/linux/dma/edma.h b/include/linux/dma/edma.h
>> index 1fafd5b0e315..a6c5728f03d3 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_sep_sz;
>>   };
>>
>>   /* Export to the platform drivers */
>> --
>> 2.43.0
>>