The real issue is that some devices (xgmac, I am looking at you), don't
set the dma_mask, even though they are perfectly capable of doing dma.

Maybe I should modify the arm implementation of dma_capable (see
http://marc.info/?l=linux-kernel&m=138029832007821&w=2) to ignore the
dma_mask.

On Mon, 30 Sep 2013, Konrad Rzeszutek Wilk wrote:

On Fri, Sep 27, 2013 at 05:10:03PM +0100, Stefano Stabellini wrote:

Why? I am looking at X86 and IA64 and I see:

 79         if (!dev->dma_mask)                                                     
 80                 return 0;           


Why not port dma_capable over to ARM?

quoted

Signed-off-by: Stefano Stabellini <redacted>
---
 drivers/xen/swiotlb-xen.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 790c2eb..3011736 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c

@@ -512,7 +512,7 @@ dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
 	 * buffering it.
 	 */
 	if (!xen_feature(XENFEAT_auto_translated_physmap) &&
-	    dma_capable(dev, dev_addr, size) &&
+	    dev->dma_mask && dma_capable(dev, dev_addr, size) &&
 	    !range_straddles_page_boundary(phys, size) && !swiotlb_force)
 		return dev_addr;
 

@@ -532,7 +532,7 @@ dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
 	/*
 	 * Ensure that the address returned is DMA'ble
 	 */
-	if (!dma_capable(dev, dev_addr, size)) {
+	if (dev->dma_mask && !dma_capable(dev, dev_addr, size)) {
 		swiotlb_tbl_unmap_single(dev, map, size, dir);
 		dev_addr = 0;
 	}

@@ -660,7 +660,7 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
 
 		if (swiotlb_force ||
 		    xen_feature(XENFEAT_auto_translated_physmap) ||
-		    !dma_capable(hwdev, dev_addr, sg->length) ||
+		    (hwdev->dma_mask && !dma_capable(hwdev, dev_addr, sg->length)) ||
 		    range_straddles_page_boundary(paddr, sg->length)) {
 			/*
 			 * Pass the dma_addr of the first slab in the iotlb buffer as

-- 
1.7.2.5