[PATCH v2] dmaengine: rcar-dmac: Widen DMA mask to 40 bits

[PATCH v2] dmaengine: rcar-dmac: Widen DMA mask to 40 bits

[Geert Uytterhoeven]

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 <geert+renesas@glider.be>
---
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

Re: [PATCH v2] dmaengine: rcar-dmac: Widen DMA mask to 40 bits

[Vinod Koul]

On Mon, Feb 13, 2017 at 12:00:26PM +0100, Geert Uytterhoeven wrote:
> 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.

Applied, thanks

-- 
~Vinod