linux-kernel - Re: [PATCH v6 15/19] swiotlb-xen: call dma_capable only if dev->dma

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Date:	Wed, 2 Oct 2013 18:13:35 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	<xen-devel@...ts.xensource.com>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Ian Campbell <Ian.Campbell@...rix.com>,
	<rob.herring@...xeda.com>
Subject: Re: [PATCH v6 15/19] swiotlb-xen: call dma_capable only if dev->dma_mask
 is allocated

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?
> 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> > ---
> >  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
> > 
> 
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