By default, the DMA mask covers only the low 32-bit address space, which causes SWIOTLB on arm64 to fall back to a bounce buffer for DMA transfers involving memory outside the 32-bit address space.
The R-Car DMA controller hardware supports a 40-bit address space, hence widen the DMA mask to 40 bits to actually make use of this feature. Signed-off-by: Geert Uytterhoeven <[email protected]> --- Note that for proper operation in the presence of an enabled IOMMU, you also need commit 3b6bb5b705a4051c ("iommu/ipmmu-vmsa: Restrict IOMMU Domain Geometry to 32-bit address space") in iommu/next. However, as the IOMMU is not enabled in upstream nor linux-next, it is safe to apply this patch in parallel. v2: - No changes. --- drivers/dma/sh/rcar-dmac.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c index 2e441d0ccd79a37a..93a69b992a51a7aa 100644 --- a/drivers/dma/sh/rcar-dmac.c +++ b/drivers/dma/sh/rcar-dmac.c @@ -1716,6 +1716,7 @@ static int rcar_dmac_probe(struct platform_device *pdev) dmac->dev = &pdev->dev; platform_set_drvdata(pdev, dmac); + dma_set_mask_and_coherent(dmac->dev, DMA_BIT_MASK(40)); ret = rcar_dmac_parse_of(&pdev->dev, dmac); if (ret < 0) -- 1.9.1
