Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751901AbZKPRna (ORCPT ); Mon, 16 Nov 2009 12:43:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751033AbZKPRn3 (ORCPT ); Mon, 16 Nov 2009 12:43:29 -0500 Received: from eddie.linux-mips.org ([78.24.191.182]:34267 "EHLO eddie.linux-mips.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750995AbZKPRn3 (ORCPT ); Mon, 16 Nov 2009 12:43:29 -0500 Date: Mon, 16 Nov 2009 18:43:24 +0100 From: Ralf Baechle To: Takashi Iwai , Thomas Bogendoerfer Cc: 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: <20091116174324.GA17748@linux-mips.org> References: <9cbcd06037c18288a6493459b8f3a6e1562eca77.1258389992.git.wuzhangjin@gmail.com> 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: 1908 Lines: 48 On Mon, Nov 16, 2009 at 06:12:22PM +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. 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? 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/