LinuxTV Patchwork [v4,02/10,media] marvell-ccic: fix DMA s/g desc number calculation

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Submitter Lubomir Rintel
Date April 29, 2019, 9:16 a.m.
Message ID <>
Download mbox | patch
Permalink /patch/55927/
State Accepted
Delegated to: Hans Verkuil
Headers show


Lubomir Rintel - April 29, 2019, 9:16 a.m.
The commit d790b7eda953 ("[media] vb2-dma-sg: move dma_(un)map_sg here")
left dma_desc_nent unset. It previously contained the number of DMA
descriptors as returned from dma_map_sg().

We can now (since the commit referred to above) obtain the same value from
the sg_table and drop dma_desc_nent altogether.

Tested on OLPC XO-1.75 machine. Doesn't affect the OLPC XO-1's Cafe
driver, since that one doesn't do DMA.

Fixes: d790b7eda953df474f470169ebdf111c02fa7a2d
Signed-off-by: Lubomir Rintel <>
 drivers/media/platform/marvell-ccic/mcam-core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)


diff --git a/drivers/media/platform/marvell-ccic/mcam-core.c b/drivers/media/platform/marvell-ccic/mcam-core.c
index f1b301810260..d97f39bde9bd 100644
--- a/drivers/media/platform/marvell-ccic/mcam-core.c
+++ b/drivers/media/platform/marvell-ccic/mcam-core.c
@@ -200,7 +200,6 @@  struct mcam_vb_buffer {
 	struct list_head queue;
 	struct mcam_dma_desc *dma_desc;	/* Descriptor virtual address */
 	dma_addr_t dma_desc_pa;		/* Descriptor physical address */
-	int dma_desc_nent;		/* Number of mapped descriptors */
 static inline struct mcam_vb_buffer *vb_to_mvb(struct vb2_v4l2_buffer *vb)
@@ -608,9 +607,11 @@  static void mcam_dma_contig_done(struct mcam_camera *cam, int frame)
 static void mcam_sg_next_buffer(struct mcam_camera *cam)
 	struct mcam_vb_buffer *buf;
+	struct sg_table *sg_table;
 	buf = list_first_entry(&cam->buffers, struct mcam_vb_buffer, queue);
+	sg_table = vb2_dma_sg_plane_desc(&buf->vb_buf.vb2_buf, 0);
 	 * Very Bad Not Good Things happen if you don't clear
 	 * C1_DESC_ENA before making any descriptor changes.
@@ -618,7 +619,7 @@  static void mcam_sg_next_buffer(struct mcam_camera *cam)
 	mcam_reg_clear_bit(cam, REG_CTRL1, C1_DESC_ENA);
 	mcam_reg_write(cam, REG_DMA_DESC_Y, buf->dma_desc_pa);
 	mcam_reg_write(cam, REG_DESC_LEN_Y,
-			buf->dma_desc_nent*sizeof(struct mcam_dma_desc));
+			sg_table->nents*sizeof(struct mcam_dma_desc));
 	mcam_reg_write(cam, REG_DESC_LEN_U, 0);
 	mcam_reg_write(cam, REG_DESC_LEN_V, 0);
 	mcam_reg_set_bit(cam, REG_CTRL1, C1_DESC_ENA);

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