Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757180AbZKROVc (ORCPT ); Wed, 18 Nov 2009 09:21:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757083AbZKROVc (ORCPT ); Wed, 18 Nov 2009 09:21:32 -0500 Received: from eddie.linux-mips.org ([78.24.191.182]:40946 "EHLO eddie.linux-mips.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757059AbZKROVb (ORCPT ); Wed, 18 Nov 2009 09:21:31 -0500 Date: Wed, 18 Nov 2009 15:20:56 +0100 From: Ralf Baechle To: Takashi Iwai Cc: Thomas Bogendoerfer , Wu Zhangjin , Jaroslav Kysela , alsa-devel@alsa-project.org, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, Wu Zhangjin Subject: Re: [PATCH] MIPS: Fixups of ALSA memory maps Message-ID: <20091118142056.GB6615@linux-mips.org> References: <9cbcd06037c18288a6493459b8f3a6e1562eca77.1258389992.git.wuzhangjin@gmail.com> <20091116174324.GA17748@linux-mips.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2566 Lines: 64 On Tue, Nov 17, 2009 at 10:29:10AM +0100, Takashi Iwai wrote: > > > Actually, this has been a looong-standing problem. > > > I have a series of patches to fix these issues, but it's more > > > intensively involved with dma_*() functions. > > > > > > The patches can be found in test/dma-fix branch of sound GIT tree. > > > git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6.git test/dma-fix > > > > > > This basically adds dma_mmap_coherent() function to feasible > > > architectures, which is already implemented for ARM, so far. > > > > Cool - but needs a little further tweaking to work right. That's a > > solution which will use uncached accesses on all MIPS systems. > > > > IP27/IP35-family machines will explode when you try that. Eventually the > > cache coherency logic will notice that cache, directory caches and memory > > have become inconsistent and bombard the CPU with a bunch of nasty > > exceptions. > > OK, that's really bad. Hardware designers do such things to you. Often even for a reason. > > For cache-coherent machines otoh it's a big waste of performance. > > > > int dma_mmap_coherent(struct device *dev, struct vm_area_struct *vma, > > void *cpu_addr, dma_addr_t handle, size_t size) > > { > > struct page *pg; > > > > if (!plat_device_is_coherent(dev)) > > vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); > > cpu_addr = (void *)dma_addr_to_virt(handle); > > pg = virt_to_page(cpu_addr); > > > > return remap_pfn_range(vma, vma->vm_start, > > page_to_pfn(pg) + vma->vm_pgoff, > > size, vma->vm_page_prot); > > } > > EXPORT_SYMBOL(dma_mmap_coherent); > > > > Thomas - you're the IP28 specialist. Would the plat_device_is_coherent() > > above have to become a cpu_is_noncoherent_r10000() call? Any further > > nasties? > > Thanks for checking! You're welcome! So basically I'd not mind putting this into the Linux/MIPS tree; we still can iron out the kinks from there on and probably much better than by having arch stuff in the ALSA tree. I recall this new API having been posted for discussion to linux-arch. What was the outcome? I'd only like to add a new API if the other arch maintainers see it fit their needs also. Ralf -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/