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Date:   Fri, 11 May 2018 16:52:25 +0530
From:   Vinod Koul <vkoul@kernel.org>
To:     Baolin Wang <baolin.wang@linaro.org>
Cc:     dan.j.williams@intel.com, vinod.koul@intel.com,
        eric.long@spreadtrum.com, broonie@kernel.org, lars@metafoo.de,
        dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] dmaengine: sprd: Add Spreadtrum DMA configuration
Message-ID: <20180511112225.GA30118@vkoul-mobl>
References: <b115795adf9e9a9e611ee0ff353fae5850d1e287.1525863923.git.baolin.wang@linaro.org>
 <67447aabb8e4e051ff39b814a0e169e6a91bb66e.1525863923.git.baolin.wang@linaro.org>
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In-Reply-To: <67447aabb8e4e051ff39b814a0e169e6a91bb66e.1525863923.git.baolin.wang@linaro.org>
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On 09-05-18, 19:12, Baolin Wang wrote:

> +/*
> + * struct sprd_dma_config - DMA configuration structure
> + * @cfg: dma slave channel runtime config
> + * @src_addr: the source physical address
> + * @dst_addr: the destination physical address
> + * @block_len: specify one block transfer length
> + * @transcation_len: specify one transcation transfer length
> + * @src_step: source transfer step
> + * @dst_step: destination transfer step
> + * @wrap_ptr: wrap pointer address, once the transfer address reaches the
> + * 'wrap_ptr', the next transfer address will jump to the 'wrap_to' address.
> + * @wrap_to: wrap jump to address
> + * @req_mode: specify the DMA request mode
> + * @int_mode: specify the DMA interrupt type
> + */
> +struct sprd_dma_config {
> +	struct dma_slave_config cfg;
> +	phys_addr_t src_addr;
> +	phys_addr_t dst_addr;

these are already in cfg so why duplicate, same for few more here.

> +static enum sprd_dma_datawidth
> +sprd_dma_get_datawidth(enum dma_slave_buswidth buswidth)
> +{
> +	switch (buswidth) {
> +	case DMA_SLAVE_BUSWIDTH_1_BYTE:
> +		return SPRD_DMA_DATAWIDTH_1_BYTE;
> +
> +	case DMA_SLAVE_BUSWIDTH_2_BYTES:
> +		return SPRD_DMA_DATAWIDTH_2_BYTES;
> +
> +	case DMA_SLAVE_BUSWIDTH_4_BYTES:
> +		return SPRD_DMA_DATAWIDTH_4_BYTES;
> +
> +	case DMA_SLAVE_BUSWIDTH_8_BYTES:
> +		return SPRD_DMA_DATAWIDTH_8_BYTES;
> +
> +	default:
> +		return SPRD_DMA_DATAWIDTH_4_BYTES;

what is the logic of translation here, sometime you might be able to do that
with logical operators, see other drivers..

> +	}
> +}
> +
> +static u32 sprd_dma_get_step(enum dma_slave_buswidth buswidth)
> +{
> +	switch (buswidth) {
> +	case DMA_SLAVE_BUSWIDTH_1_BYTE:
> +		return SPRD_DMA_BYTE_STEP;
> +
> +	case DMA_SLAVE_BUSWIDTH_2_BYTES:
> +		return SPRD_DMA_SHORT_STEP;
> +
> +	case DMA_SLAVE_BUSWIDTH_4_BYTES:
> +		return SPRD_DMA_WORD_STEP;
> +
> +	case DMA_SLAVE_BUSWIDTH_8_BYTES:
> +		return SPRD_DMA_DWORD_STEP;
> +
> +	default:
> +		return SPRD_DMA_DWORD_STEP;
> +	}

here as well

> +}
> +
> +static int sprd_dma_config(struct dma_chan *chan, struct sprd_dma_desc *sdesc,
> +			   struct sprd_dma_config *slave_cfg)
> +{
> +	struct sprd_dma_dev *sdev = to_sprd_dma_dev(chan);
> +	struct sprd_dma_chn *schan = to_sprd_dma_chan(chan);
> +	struct sprd_dma_chn_hw *hw = &sdesc->chn_hw;
> +	u32 fix_mode = 0, fix_en = 0, wrap_en = 0, wrap_mode = 0;
> +	u32 src_datawidth, dst_datawidth;
> +
> +	if (slave_cfg->cfg.slave_id)
> +		schan->dev_id = slave_cfg->cfg.slave_id;
> +
> +	hw->cfg = SPRD_DMA_DONOT_WAIT_BDONE << SPRD_DMA_WAIT_BDONE_OFFSET;
> +	hw->wrap_ptr = (u32)((slave_cfg->wrap_ptr & SPRD_DMA_LOW_ADDR_MASK) |

why cast?

> +		((slave_cfg->src_addr >> SPRD_DMA_HIGH_ADDR_OFFSET) &
> +		 SPRD_DMA_HIGH_ADDR_MASK));

more readable would be:

        temp = slave_cfg->wrap_ptr & SPRD_DMA_LOW_ADDR_MASK;
        temp |= slave_cfg->src_addr >> SPRD_DMA_HIGH_ADDR_OFFSET;
        temp &= SPRD_DMA_HIGH_ADDR_MASK;

and then assign... could help readability in few places...

> +	hw->wrap_to = (u32)((slave_cfg->wrap_to & SPRD_DMA_LOW_ADDR_MASK) |
> +		((slave_cfg->dst_addr >> SPRD_DMA_HIGH_ADDR_OFFSET) &
> +		 SPRD_DMA_HIGH_ADDR_MASK));
> +
> +	hw->src_addr = (u32)(slave_cfg->src_addr & SPRD_DMA_LOW_ADDR_MASK);
> +	hw->des_addr = (u32)(slave_cfg->dst_addr & SPRD_DMA_LOW_ADDR_MASK);
> +
> +	if ((slave_cfg->src_step != 0 && slave_cfg->dst_step != 0)
> +	    || (slave_cfg->src_step | slave_cfg->dst_step) == 0) {
> +		fix_en = 0;
> +	} else {
> +		fix_en = 1;
> +		if (slave_cfg->src_step)
> +			fix_mode = 1;
> +		else
> +			fix_mode = 0;
> +	}
> +
> +	if (slave_cfg->wrap_ptr && slave_cfg->wrap_to) {
> +		wrap_en = 1;
> +		if (slave_cfg->wrap_to == slave_cfg->src_addr) {
> +			wrap_mode = 0;
> +		} else if (slave_cfg->wrap_to == slave_cfg->dst_addr) {
> +			wrap_mode = 1;
> +		} else {
> +			dev_err(sdev->dma_dev.dev, "invalid wrap mode\n");
> +			return -EINVAL;
> +		}
> +	}
> +
> +	hw->intc = slave_cfg->int_mode | SPRD_DMA_CFG_ERR_INT_EN;
> +
> +	src_datawidth = sprd_dma_get_datawidth(slave_cfg->cfg.src_addr_width);
> +	dst_datawidth = sprd_dma_get_datawidth(slave_cfg->cfg.dst_addr_width);
> +	hw->frg_len = src_datawidth << SPRD_DMA_SRC_DATAWIDTH_OFFSET |
> +		dst_datawidth << SPRD_DMA_DES_DATAWIDTH_OFFSET |
> +		slave_cfg->req_mode << SPRD_DMA_REQ_MODE_OFFSET |
> +		wrap_mode << SPRD_DMA_WRAP_SEL_OFFSET |
> +		wrap_en << SPRD_DMA_WRAP_EN_OFFSET |
> +		fix_mode << SPRD_DMA_FIX_SEL_OFFSET |
> +		fix_en << SPRD_DMA_FIX_EN_OFFSET |
> +		(slave_cfg->cfg.src_maxburst & SPRD_DMA_FRG_LEN_MASK);

sorry this is not at all readable...

> +static struct dma_async_tx_descriptor *
> +sprd_dma_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
> +		       unsigned int sglen, enum dma_transfer_direction dir,
> +		       unsigned long flags, void *context)
> +{
> +	struct sprd_dma_chn *schan = to_sprd_dma_chan(chan);
> +	struct sprd_dma_config *slave_cfg = &schan->slave_cfg;
> +	struct sprd_dma_desc *sdesc;
> +	struct scatterlist *sg;
> +	int ret, i;
> +
> +	/* TODO: now we only support one sg for each DMA configuration. */

thats a SW limit right and you will fix it later?

> +	if (!is_slave_direction(dir) || sglen > 1)
> +		return NULL;
> +
> +	sdesc = kzalloc(sizeof(*sdesc), GFP_NOWAIT);
> +	if (!sdesc)
> +		return NULL;
> +
> +	for_each_sg(sgl, sg, sglen, i) {
> +		if (dir == DMA_MEM_TO_DEV) {
> +			slave_cfg->src_addr = sg_dma_address(sg);
> +			slave_cfg->dst_addr = slave_cfg->cfg.dst_addr;
> +			slave_cfg->src_step =
> +			sprd_dma_get_step(slave_cfg->cfg.src_addr_width);
> +			slave_cfg->dst_step = SPRD_DMA_NONE_STEP;
> +		} else {
> +			slave_cfg->src_addr = slave_cfg->cfg.src_addr;
> +			slave_cfg->dst_addr = sg_dma_address(sg);
> +			slave_cfg->src_step = SPRD_DMA_NONE_STEP;
> +			slave_cfg->dst_step =
> +			sprd_dma_get_step(slave_cfg->cfg.dst_addr_width);

use a helper for filling this and passing right values for each case?

-- 
~Vinod