Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751635Ab3HBLmk (ORCPT ); Fri, 2 Aug 2013 07:42:40 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:30137 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751571Ab3HBLmh (ORCPT ); Fri, 2 Aug 2013 07:42:37 -0400 X-IronPort-AV: E=Sophos;i="4.89,800,1367971200"; d="scan'208";a="39019328" Date: Fri, 2 Aug 2013 12:42:16 +0100 From: Stefano Stabellini X-X-Sender: sstabellini@kaball.uk.xensource.com To: Russell King - ARM Linux CC: Stefano Stabellini , , , , , , Subject: Re: [PATCH v2 RFC 2/8] arm: introduce a global dma_ops pointer In-Reply-To: <20130731200135.GZ24642@n2100.arm.linux.org.uk> Message-ID: References: <1375300452-12545-2-git-send-email-stefano.stabellini@eu.citrix.com> <20130731200135.GZ24642@n2100.arm.linux.org.uk> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1525 Lines: 32 On Wed, 31 Jul 2013, Russell King - ARM Linux wrote: > On Wed, Jul 31, 2013 at 08:54:06PM +0100, Stefano Stabellini wrote: > > Initially set dma_ops to arm_dma_ops. > > Use dma_ops instead of arm_dma_ops in dmabounce. > > > > Signed-off-by: Stefano Stabellini > > CC: will.deacon@arm.com > > CC: linux@arm.linux.org.uk > > If you're using swiotlb, there's little point in converting dmabounce > to be able to use it, because it's basically providing the same > functionality - dmabounce is there to do software buffer bouncing within > the DMA to move streaming buffers from DMA-inaccessible memory into > DMA-accessible memory. > > It's original use is with older SoCs with buggy DMA (eg, those which > can only address alternate 1MB chunks of memory for example) but also > got used in situations where alternative solutions would've been better > (like using swiotlb.) I've been discouraging its use as it's suffered > from memory exhaustion problems (there's a number of threads and bug > reports which were never solved about IXP4xx(?) platforms suffering > this due to this bouncing.) OK, I'll let dmabounce keep using arm_dma_ops directly (instead of dma_ops). Should I add "depends on !DMABOUNCE" to the SWIOTLB Kconfig entry too? -- 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/