Hi,
could you put this on hold for the moment, I've noticed that a
sg_free_table is actually missing in this patch, leading to a memory
leak. I'll thus post a v2 of the patch shortly.
Cheers,
Alain
On Mon, Jan 10, 2022 at 11:37:39AM +0100, Alain Volmat wrote:
> 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.
>
> Signed-off-by: Alain Volmat <alain.volmat@xxxxxxxxxxx>
> ---
> drivers/media/platform/stm32/stm32-dcmi.c | 47 ++++++++++++++++++-----
> 1 file changed, 37 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/media/platform/stm32/stm32-dcmi.c b/drivers/media/platform/stm32/stm32-dcmi.c
> index e1b17c05229c..ee170e999a88 100644
> --- a/drivers/media/platform/stm32/stm32-dcmi.c
> +++ b/drivers/media/platform/stm32/stm32-dcmi.c
> @@ -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);
> --
> 2.25.1
>
