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: Alain Volmat <alain.volmat@foss.st.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

diff --git a/drivers/media/platform/stm32/stm32-dcmi.c b/drivers/media/platform/stm32/stm32-dcmi.c
index e1b17c05229cf7afd972cbd2baeac159c1f82896..bf76b420352dc64abf0607bf96ac54a6b8dba141 100644 (file)
--- 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,
-                                          DMA_DEV_TO_MEM,
-                                          DMA_PREP_INTERRUPT);
+       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);