Re: [PATCH v5 2/3] dmaengine: amlogic: Add general DMA driver for A9

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

On Wed, Mar 04, 2026 at 06:14:13AM +0000, Xianwei Zhao wrote:
> Amlogic A9 SoCs include a general-purpose DMA controller that can be used
> by multiple peripherals, such as I2C PIO and I3C. Each peripheral group
> is associated with a dedicated DMA channel in hardware.
>
> Signed-off-by: Xianwei Zhao <xianwei.zhao@amlogic.com>
> ---
>  drivers/dma/Kconfig       |   9 +
>  drivers/dma/Makefile      |   1 +
>  drivers/dma/amlogic-dma.c | 585 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 595 insertions(+)
>
...
> +
> +static int aml_dma_alloc_chan_resources(struct dma_chan *chan)
> +{
> +	struct aml_dma_chan *aml_chan = to_aml_dma_chan(chan);
> +	struct aml_dma_dev *aml_dma = aml_chan->aml_dma;
> +	size_t size = size_mul(sizeof(struct aml_dma_sg_link), DMA_MAX_LINK);
> +
> +	aml_chan->sg_link = dma_alloc_coherent(aml_dma->dma_device.dev, size,
> +					       &aml_chan->sg_link_phys, GFP_KERNEL);
> +	if (!aml_chan->sg_link)
> +		return  -ENOMEM;
> +
> +	/* offset is the same RCH_CFG and WCH_CFG */
> +	regmap_update_bits(aml_dma->regmap, aml_chan->reg_offs + RCH_CFG, CFG_CLEAR, CFG_CLEAR);

regmap_set_bits()

> +	aml_chan->status = DMA_COMPLETE;
> +	dma_async_tx_descriptor_init(&aml_chan->desc, chan);
> +	aml_chan->desc.tx_submit = aml_dma_tx_submit;
> +	regmap_update_bits(aml_dma->regmap, aml_chan->reg_offs + RCH_CFG, CFG_CLEAR, 0);

regmap_clear_bits();

> +
> +	return 0;
> +}
> +
> +static void aml_dma_free_chan_resources(struct dma_chan *chan)
> +{
> +	struct aml_dma_chan *aml_chan = to_aml_dma_chan(chan);
> +	struct aml_dma_dev *aml_dma = aml_chan->aml_dma;
> +
> +	aml_chan->status = DMA_COMPLETE;
> +	dma_free_coherent(aml_dma->dma_device.dev,
> +			  sizeof(struct aml_dma_sg_link) * DMA_MAX_LINK,
> +			  aml_chan->sg_link, aml_chan->sg_link_phys);
> +}
> +
...
> +
> +static struct dma_async_tx_descriptor *aml_dma_prep_slave_sg
> +		(struct dma_chan *chan, struct scatterlist *sgl,
> +		unsigned int sg_len, enum dma_transfer_direction direction,
> +		unsigned long flags, void *context)
> +{
> +	struct aml_dma_chan *aml_chan = to_aml_dma_chan(chan);
> +	struct aml_dma_dev *aml_dma = aml_chan->aml_dma;
> +	struct aml_dma_sg_link *sg_link;
> +	struct scatterlist *sg;
> +	int idx = 0;
> +	u64 paddr;
> +	u32 reg, link_count, avail, chan_id;
> +	u32 i;
> +
> +	if (aml_chan->direction != direction) {
> +		dev_err(aml_dma->dma_device.dev, "direction not support\n");
> +		return NULL;
> +	}
> +
> +	switch (aml_chan->status) {
> +	case DMA_IN_PROGRESS:
> +		dev_err(aml_dma->dma_device.dev, "not support multi tx_desciptor\n");
> +		return NULL;
> +
> +	case DMA_COMPLETE:
> +		aml_chan->data_len = 0;
> +		chan_id = aml_chan->chan_id;
> +		reg = (direction == DMA_DEV_TO_MEM) ? WCH_INT_MASK : RCH_INT_MASK;
> +		regmap_update_bits(aml_dma->regmap, reg, BIT(chan_id), BIT(chan_id));
> +
> +		break;
> +	default:
> +		dev_err(aml_dma->dma_device.dev, "status error\n");
> +		return NULL;
> +	}
> +
> +	link_count = sg_nents_for_dma(sgl, sg_len, SG_MAX_LEN);
> +
> +	if (link_count > DMA_MAX_LINK) {
> +		dev_err(aml_dma->dma_device.dev,
> +			"maximum number of sg exceeded: %d > %d\n",
> +			sg_len, DMA_MAX_LINK);
> +		aml_chan->status = DMA_ERROR;
> +		return NULL;
> +	}
> +
> +	aml_chan->status = DMA_IN_PROGRESS;
> +
> +	for_each_sg(sgl, sg, sg_len, i) {
> +		avail = sg_dma_len(sg);
> +		paddr = sg->dma_address;
> +		while (avail > SG_MAX_LEN) {
> +			sg_link = &aml_chan->sg_link[idx++];
> +			/* set dma address and len  to sglink*/
> +			sg_link->address = paddr;
> +			sg_link->ctl = FIELD_PREP(LINK_LEN, SG_MAX_LEN);
> +			paddr = paddr + SG_MAX_LEN;
> +			avail = avail - SG_MAX_LEN;
> +		}
> +		sg_link = &aml_chan->sg_link[idx++];
> +		/* set dma address and len  to sglink*/
> +		sg_link->address = paddr;

Support here dma_wmb() to make previous write complete before update
OWNER BIT.

Where update OWNER bit to tall DMA engine sg_link ready?

> +		sg_link->ctl = FIELD_PREP(LINK_LEN, avail);
> +
> +		aml_chan->data_len += sg_dma_len(sg);
> +	}
> +	aml_chan->sg_link_cnt = idx;
> +
> +	return &aml_chan->desc;
> +}
> +
> +static int aml_dma_pause_chan(struct dma_chan *chan)
> +{
> +	struct aml_dma_chan *aml_chan = to_aml_dma_chan(chan);
> +	struct aml_dma_dev *aml_dma = aml_chan->aml_dma;
> +
> +	regmap_update_bits(aml_dma->regmap, aml_chan->reg_offs + RCH_CFG, CFG_PAUSE, CFG_PAUSE);

regmap_set_bits(), check others

> +	aml_chan->pre_status = aml_chan->status;
> +	aml_chan->status = DMA_PAUSED;
> +
> +	return 0;
> +}
> +
...
> +
> +	dma_set_max_seg_size(dma_dev->dev, SG_MAX_LEN);
> +
> +	dma_cap_set(DMA_SLAVE, dma_dev->cap_mask);
> +	dma_dev->device_alloc_chan_resources = aml_dma_alloc_chan_resources;
> +	dma_dev->device_free_chan_resources = aml_dma_free_chan_resources;
> +	dma_dev->device_tx_status = aml_dma_tx_status;
> +	dma_dev->device_prep_slave_sg = aml_dma_prep_slave_sg;
> +
> +	dma_dev->device_pause = aml_dma_pause_chan;
> +	dma_dev->device_resume = aml_dma_resume_chan;

align callback name, aml_dma_chan_resume()

> +	dma_dev->device_terminate_all = aml_dma_terminate_all;
> +	dma_dev->device_issue_pending = aml_dma_enable_chan;

aml_dma_issue_pending()

Frank
> +	/* PIO 4 bytes and I2C 1 byte */
> +	dma_dev->dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_4_BYTES) | BIT(DMA_SLAVE_BUSWIDTH_1_BYTE);
> +	dma_dev->directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);
> +	dma_dev->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
> +
...
> --
> 2.52.0
>