media: marvell-ccic: fix DMA s/g desc number calculation

BugLink: https://bugs.launchpad.net/bugs/1840081

[ Upstream commit 0c7aa329 ]

The commit d790b7ed ("[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.

[mchehab+samsung@kernel.org: fix a checkpatch warning]

Fixes: d790b7ed ("[media] vb2-dma-sg: move dma_(un)map_sg here")
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/media/platform/marvell-ccic/mcam-core.c

@@ -209,7 +209,6 @@ 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)
@@ -616,9 +615,11 @@ 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);
 	list_del_init(&buf->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.
@@ -626,7 +627,7 @@ 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);