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 13:22:58 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	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

On Wed, Oct 02, 2013 at 06:13:35PM +0100, Stefano Stabellini wrote:
> 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.

So this looks like a bug in the drivers. I thought I saw a huge patchset
by the ARM maintainer that tries to fix the dma_mask and dma_mask_coherent
bugs? And also fix the drivers to use the dma mask?

> 
> 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.

Or fix the 'xgmac'?
> 
> 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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