Re: [PATCH 2/2] dmaengine: hdmac: Implement interleaved transfers

[Ludovic Desroches]

On Wed, May 27, 2015 at 04:01:53PM +0200, Maxime Ripard wrote:
> The AT91 HDMAC controller supports interleaved transfers through what's
> called the Picture-in-Picture mode, which allows to transfer a squared
> portion of a framebuffer.
> 
> This means that this interleaved transfer only supports interleaved
> transfers which have a transfer size and ICGs that are fixed across all the
> chunks.
> 
> While this is a quite drastic restriction of the interleaved transfers
> compared to what the dmaengine API allows, this is still useful, and our
> driver will only reject transfers that do not conform to this.
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
One comment below, otherwise

Acked-by: Ludovic Desroches <ludovic.desroches@xxxxxxxxx>

> ---
>  drivers/dma/at_hdmac.c      | 106 ++++++++++++++++++++++++++++++++++++++++++++
>  drivers/dma/at_hdmac_regs.h |   5 +++
>  2 files changed, 111 insertions(+)
> 
> diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
> index 57b2141ddddc..59892126d175 100644
> --- a/drivers/dma/at_hdmac.c
> +++ b/drivers/dma/at_hdmac.c
> @@ -247,6 +247,10 @@ static void atc_dostart(struct at_dma_chan *atchan, struct at_desc *first)
>  	channel_writel(atchan, CTRLA, 0);
>  	channel_writel(atchan, CTRLB, 0);
>  	channel_writel(atchan, DSCR, first->txd.phys);
> +	channel_writel(atchan, SPIP, ATC_SPIP_HOLE(first->src_hole) |
> +		       ATC_SPIP_BOUNDARY(first->boundary));
> +	channel_writel(atchan, DPIP, ATC_DPIP_HOLE(first->dst_hole) |
> +		       ATC_DPIP_BOUNDARY(first->boundary));

Can't we get a trivial condition to perform these two writes only if
needed?

>  	dma_writel(atdma, CHER, atchan->mask);
>  
>  	vdbg_dump_regs(atchan);
> @@ -635,6 +639,104 @@ static dma_cookie_t atc_tx_submit(struct dma_async_tx_descriptor *tx)
>  }
>  
>  /**
> + * atc_prep_dma_interleaved - prepare memory to memory interleaved operation
> + * @chan: the channel to prepare operation on
> + * @xt: Interleaved transfer template
> + * @flags: tx descriptor status flags
> + */
> +static struct dma_async_tx_descriptor *
> +atc_prep_dma_interleaved(struct dma_chan *chan,
> +			 struct dma_interleaved_template *xt,
> +			 unsigned long flags)
> +{
> +	struct at_dma_chan	*atchan = to_at_dma_chan(chan);
> +	struct data_chunk	*first = xt->sgl;
> +	struct at_desc		*desc = NULL;
> +	size_t			xfer_count;
> +	unsigned int		dwidth;
> +	u32			ctrla;
> +	u32			ctrlb;
> +	size_t			len = 0;
> +	int			i;
> +
> +	dev_info(chan2dev(chan),
> +		 "%s: src=0x%08x, dest=0x%08x, numf=%d, frame_size=%d, flags=0x%lx\n",
> +		__func__, xt->src_start, xt->dst_start, xt->numf,
> +		xt->frame_size, flags);
> +
> +	if (unlikely(!xt || xt->numf != 1 || !xt->frame_size))
> +		return NULL;
> +
> +	/*
> +	 * The controller can only "skip" X bytes every Y bytes, so we
> +	 * need to make sure we are given a template that fit that
> +	 * description, ie a template with chunks that always have the
> +	 * same size, with the same ICGs.
> +	 */
> +	for (i = 0; i < xt->frame_size; i++) {
> +		struct data_chunk *chunk = xt->sgl + i;
> +
> +		if ((chunk->size != xt->sgl->size) ||
> +		    (dmaengine_get_dst_icg(xt, chunk) != dmaengine_get_dst_icg(xt, first)) ||
> +		    (dmaengine_get_src_icg(xt, chunk) != dmaengine_get_src_icg(xt, first))) {
> +			dev_err(chan2dev(chan),
> +				"%s: the controller can transfer only identical chunks\n",
> +				__func__);
> +			return NULL;
> +		}
> +
> +		len += chunk->size;
> +	}
> +
> +	dwidth = atc_get_xfer_width(xt->src_start,
> +				    xt->dst_start, len);
> +
> +	xfer_count = len >> dwidth;
> +	if (xfer_count > ATC_BTSIZE_MAX) {
> +		dev_err(chan2dev(chan), "%s: buffer is too big\n", __func__);
> +		return NULL;
> +	}
> +
> +	ctrla = ATC_SRC_WIDTH(dwidth) |
> +		ATC_DST_WIDTH(dwidth);
> +
> +	ctrlb =   ATC_DEFAULT_CTRLB | ATC_IEN
> +		| ATC_SRC_ADDR_MODE_INCR
> +		| ATC_DST_ADDR_MODE_INCR
> +		| ATC_SRC_PIP
> +		| ATC_DST_PIP
> +		| ATC_FC_MEM2MEM;
> +
> +	/* create the transfer */
> +	desc = atc_desc_get(atchan);
> +	if (!desc) {
> +		dev_err(chan2dev(chan),
> +			"%s: couldn't allocate our descriptor\n", __func__);
> +		return NULL;
> +	}
> +
> +	desc->lli.saddr = xt->src_start;
> +	desc->lli.daddr = xt->dst_start;
> +	desc->lli.ctrla = ctrla | xfer_count;
> +	desc->lli.ctrlb = ctrlb;
> +
> +	desc->boundary = first->size >> dwidth;
> +	desc->dst_hole = (dmaengine_get_dst_icg(xt, first) >> dwidth) + 1;
> +	desc->src_hole = (dmaengine_get_src_icg(xt, first) >> dwidth) + 1;
> +
> +	desc->txd.cookie = -EBUSY;
> +	desc->total_len = desc->len = len;
> +	desc->tx_width = dwidth;
> +
> +	/* set end-of-link to the last link descriptor of list*/
> +	set_desc_eol(desc);
> +
> +	desc->txd.flags = flags; /* client is in control of this ack */
> +
> +	return &desc->txd;
> +}
> +
> +/**
>   * atc_prep_dma_memcpy - prepare a memcpy operation
>   * @chan: the channel to prepare operation on
>   * @dest: operation virtual destination address
> @@ -1609,6 +1711,7 @@ static int __init at_dma_probe(struct platform_device *pdev)
>  	/* setup platform data for each SoC */
>  	dma_cap_set(DMA_MEMCPY, at91sam9rl_config.cap_mask);
>  	dma_cap_set(DMA_SG, at91sam9rl_config.cap_mask);
> +	dma_cap_set(DMA_INTERLEAVE, at91sam9g45_config.cap_mask);
>  	dma_cap_set(DMA_MEMCPY, at91sam9g45_config.cap_mask);
>  	dma_cap_set(DMA_SLAVE, at91sam9g45_config.cap_mask);
>  	dma_cap_set(DMA_SG, at91sam9g45_config.cap_mask);
> @@ -1713,6 +1816,9 @@ static int __init at_dma_probe(struct platform_device *pdev)
>  	atdma->dma_common.dev = &pdev->dev;
>  
>  	/* set prep routines based on capability */
> +	if (dma_has_cap(DMA_INTERLEAVE, atdma->dma_common.cap_mask))
> +		atdma->dma_common.device_prep_interleaved_dma = atc_prep_dma_interleaved;
> +
>  	if (dma_has_cap(DMA_MEMCPY, atdma->dma_common.cap_mask))
>  		atdma->dma_common.device_prep_dma_memcpy = atc_prep_dma_memcpy;
>  
> diff --git a/drivers/dma/at_hdmac_regs.h b/drivers/dma/at_hdmac_regs.h
> index 2727ca560572..bc8d5ebedd19 100644
> --- a/drivers/dma/at_hdmac_regs.h
> +++ b/drivers/dma/at_hdmac_regs.h
> @@ -196,6 +196,11 @@ struct at_desc {
>  	size_t				len;
>  	u32				tx_width;
>  	size_t				total_len;
> +
> +	/* Interleaved data */
> +	size_t				boundary;
> +	size_t				dst_hole;
> +	size_t				src_hole;
>  };
>  
>  static inline struct at_desc *
> -- 
> 2.4.1
> 
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