The vdec probe routine does not set explicit DMA constraints, leaving the driver completely dependent on platform bus default values. This lack of explicit layout initialization can lead to allocation failures, restricted address space mappings, or broken contiguous buffer handling on architectures with restrictive DMA layers.
Address these platform constraints with the following changes during driver initialization: 1. Enforce a 32-bit coherent DMA allocation window by invoking dma_set_mask_and_coherent() with a DMA_BIT_MASK(32) argument. 2. Maximize the contiguous allocation segment boundary constraint to UINT_MAX using the vb2_dma_contig_set_max_seg_size() configuration helper. This guarantees that large, contiguous video frame allocation requests work reliably and explicitly aligns the memory management paths with standard Linux kernel DMA management paradigms. Cc: Nicolas Dufresne <[email protected]> Signed-off-by: Anand Moon <[email protected]> --- drivers/staging/media/meson/vdec/vdec.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/staging/media/meson/vdec/vdec.c b/drivers/staging/media/meson/vdec/vdec.c index ac86a9c4febff..d33cbebc4453b 100644 --- a/drivers/staging/media/meson/vdec/vdec.c +++ b/drivers/staging/media/meson/vdec/vdec.c @@ -1186,6 +1186,16 @@ static int vdec_probe(struct platform_device *pdev) if (IS_ERR(core->canvas)) return PTR_ERR(core->canvas); + /* Enforce strict 32-bit DMA limit to match hardware capabilities */ + ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32)); + if (ret) + return dev_err_probe(dev, ret, "Failed to set 32-bit 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
