Commit c1b40335 authored by Alain Volmat's avatar Alain Volmat Committed by Mauro Carvalho Chehab
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media: stm32: dcmi: create a dma scatterlist based on DMA max_sg_burst value 



Prior to submitting a transfer to the DMA, the client should first check
the capabilities of the DMA channel in term of maximum of each segment.
This is given by the max_sg_burst value reported by dma_get_slave_caps API.
Based on that, if the transfer is larger than what can be handled by the
DMA channel, we split the transfer into several scatterlist elements.

[hverkuil: fix checkpatch parenthesis alignment warning]

Signed-off-by: default avatarAlain Volmat <alain.volmat@foss.st.com>
Signed-off-by: default avatarHans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@kernel.org>
parent fc5004e5

drivers/media/platform/stm32/stm32-dcmi.c

+39 −12
Original line number Diff line number Diff line
@@ -113,7 +113,7 @@ struct dcmi_framesize { 
struct dcmi_buf {

	struct vb2_v4l2_buffer	vb;

	bool			prepared;

	dma_addr_t		paddr;

	struct sg_table		sgt;

	size_t			size;

	struct list_head	list;

};
@@ -157,6 +157,7 @@ struct stm32_dcmi { 
	enum state			state;

	struct dma_chan			*dma_chan;

	dma_cookie_t			dma_cookie;

	u32				dma_max_burst;

	u32				misr;

	int				errors_count;

	int				overrun_count;
@@ -326,13 +327,11 @@ static int dcmi_start_dma(struct stm32_dcmi *dcmi, 
	mutex_lock(&dcmi->dma_lock);



	/* Prepare a DMA transaction */

	desc = dmaengine_prep_slave_single(dcmi->dma_chan, buf->paddr,

					   buf->size,

	desc = dmaengine_prep_slave_sg(dcmi->dma_chan, buf->sgt.sgl, buf->sgt.nents,

				       DMA_DEV_TO_MEM,

				       DMA_PREP_INTERRUPT);

	if (!desc) {

		dev_err(dcmi->dev, "%s: DMA dmaengine_prep_slave_single failed for buffer phy=%pad size=%zu\n",

			__func__, &buf->paddr, buf->size);

		dev_err(dcmi->dev, "%s: DMA dmaengine_prep_slave_sg failed\n", __func__);

		mutex_unlock(&dcmi->dma_lock);

		return -EINVAL;

	}
@@ -524,6 +523,10 @@ static int dcmi_buf_prepare(struct vb2_buffer *vb) 
	struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);

	struct dcmi_buf *buf = container_of(vbuf, struct dcmi_buf, vb);

	unsigned long size;

	unsigned int num_sgs = 1;

	dma_addr_t dma_buf;

	struct scatterlist *sg;

	int i, ret;



	size = dcmi->fmt.fmt.pix.sizeimage;
@@ -537,15 +540,33 @@ static int dcmi_buf_prepare(struct vb2_buffer *vb) 


	if (!buf->prepared) {

		/* Get memory addresses */

		buf->paddr =

			vb2_dma_contig_plane_dma_addr(&buf->vb.vb2_buf, 0);

		buf->size = vb2_plane_size(&buf->vb.vb2_buf, 0);

		buf->prepared = true;

		if (buf->size > dcmi->dma_max_burst)

			num_sgs = DIV_ROUND_UP(buf->size, dcmi->dma_max_burst);



		vb2_set_plane_payload(&buf->vb.vb2_buf, 0, buf->size);

		ret = sg_alloc_table(&buf->sgt, num_sgs, GFP_ATOMIC);

		if (ret) {

			dev_err(dcmi->dev, "sg table alloc failed\n");

			return ret;

		}



		dma_buf = vb2_dma_contig_plane_dma_addr(&buf->vb.vb2_buf, 0);



		dev_dbg(dcmi->dev, "buffer[%d] phy=%pad size=%zu\n",

			vb->index, &buf->paddr, buf->size);

			vb->index, &dma_buf, buf->size);



		for_each_sg(buf->sgt.sgl, sg, num_sgs, i) {

			size_t bytes = min_t(size_t, size, dcmi->dma_max_burst);



			sg_dma_address(sg) = dma_buf;

			sg_dma_len(sg) = bytes;

			dma_buf += bytes;

			size -= bytes;

		}



		buf->prepared = true;



		vb2_set_plane_payload(&buf->vb.vb2_buf, 0, buf->size);

	}



	return 0;
@@ -1866,6 +1887,7 @@ static int dcmi_probe(struct platform_device *pdev) 
	struct stm32_dcmi *dcmi;

	struct vb2_queue *q;

	struct dma_chan *chan;

	struct dma_slave_caps caps;

	struct clk *mclk;

	int irq;

	int ret = 0;
@@ -1953,6 +1975,11 @@ static int dcmi_probe(struct platform_device *pdev) 
		return ret;

	}



	dcmi->dma_max_burst = UINT_MAX;

	ret = dma_get_slave_caps(chan, &caps);

	if (!ret && caps.max_sg_burst)

		dcmi->dma_max_burst = caps.max_sg_burst	* DMA_SLAVE_BUSWIDTH_4_BYTES;



	spin_lock_init(&dcmi->irqlock);

	mutex_init(&dcmi->lock);

	mutex_init(&dcmi->dma_lock);