Subject: [PATCH v6 6/8] media: meson: vdec: Configure DMA mask and segment size in probe

From: Anand Moon <[email-masked]>
Date: Sat, 30 May 2026 15:12:52 +0530

The vdec probe routine did not set explicit DMA constraints,
leaving the driver dependent on platform defaults. This could
cause allocation failures or fragmented buffer handling on
systems with stricter DMA limits.

Fix this by:
- Setting a 64 bit coherent DMA mask with
  dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)).
- Configuring the maximum contiguous segment size to UINT_MAX
  via vb2_dma_contig_set_max_seg_size().

This aligns the driver with common DMA setup practices and guarantees
large buffer allocations work reliably across platforms.

Cc: Nicolas Dufresne <[email-masked]>
Reported-by: Sashiko <[email-masked]>
Closes: https://lore.kernel.org/all/[email-masked]/
Fixes: 3e7f51bd9607 ("media: meson: add v4l2 m2m video decoder driver")
Signed-off-by: Anand Moon <[email-masked]>
---
 drivers/staging/media/meson/vdec/vdec.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/staging/media/meson/vdec/vdec.c b/drivers/staging/media/meson/vdec/vdec.c
index 4884ee04b352..f99335effe17 100644
--- a/drivers/staging/media/meson/vdec/vdec.c
+++ b/drivers/staging/media/meson/vdec/vdec.c
@@ -1064,6 +1064,15 @@ static int vdec_probe(struct platform_device *pdev)
 	if (IS_ERR(core->canvas))
 		return PTR_ERR(core->canvas);
 
+	ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64));
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to set DMA mask\n");
+
+	ret = vb2_dma_contig_set_max_seg_size(dev, UINT_MAX);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "Failed to set DMA max segment size\n");
+
 	of_id = of_match_node(vdec_dt_match, dev->of_node);
 	core->platform = of_id->data;
 
-- 
2.50.1