From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: [LINUX] dma: Use swiotlb mask for coherent mappings too Date: Wed, 20 Dec 2006 11:55:10 +0000 Message-ID: References: <4589319B.76E4.0078.0@novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4589319B.76E4.0078.0@novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Jan Beulich , Herbert Xu , Keir Fraser Cc: Xen Development Mailing List , Calvin Webster List-Id: xen-devel@lists.xenproject.org We could fall back to swiotlb_alloc/free_coherent? I took the patch but renamed io_tlb_dma_bits to dma_bits. This makes more sense for users anyway I think -- they're unlikely to care whether allocations go thru swiotlb or not, they just want to specify what device limitation they require the kernel to handle by whatever means it chooses. So now it's 'dma_bits=' rather than 'io_tlb_dma_bits=', which happens to neatly be the same as the Xen boot parameter's name. -- Keir On 20/12/06 11:50, "Jan Beulich" wrote: > As we're going to have a swiotlb_{alloc,free}_coherent implementation after > the sync > with lib/swiotlb.c anyway, wouldn't it make sense to have > dma_{alloc,free}_coherent > call the former rather than setting up things by itself? If course, this will > increase > pressure on the swiotlb memory, but otoh it could reduce the likelihood of the > contiguous region setup failing (especially if those are of non-zero order). > > Jan > >>>> Herbert Xu 20.12.06 06:14 >>> > Hi Keir: > > [LINUX] dma: Use swiotlb mask for coherent mappings too > > The recent change to use a default DMA bit width of 30 bits (required > by chips like the b44) only converted the streaming DMA primitives. > The coherent mappings are still hard-coded to 31 bits. This means that > b44 still doesn't work under Xen. > > This patch makes the io_tlb_dma_bits variable global and uses it for > coherent memory mappings. > > Thanks to Calvin Webster for providing a machine with a b44 and 2G > of memory I've been able to verify that this finally makes the b44 > work under Xen. > > Signed-off-by: Herbert Xu > > Cheers,