Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754001AbbGCLXd (ORCPT ); Fri, 3 Jul 2015 07:23:33 -0400 Received: from mail-wi0-f176.google.com ([209.85.212.176]:35687 "EHLO mail-wi0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755070AbbGCLXZ (ORCPT ); Fri, 3 Jul 2015 07:23:25 -0400 MIME-Version: 1.0 In-Reply-To: <20150703090305.GR7557@n2100.arm.linux.org.uk> References: <1435699746-21395-1-git-send-email-lorenx4@gmail.com> <20150701111251.GA21981@e104818-lin.cambridge.arm.com> <20150703090305.GR7557@n2100.arm.linux.org.uk> Date: Fri, 3 Jul 2015 13:23:24 +0200 Message-ID: Subject: Re: [PATCH v5] arm DMA: Fix allocation from CMA for coherent DMA From: Lorenzo Nava To: Russell King - ARM Linux Cc: Catalin Marinas , Arnd Bergmann , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1721 Lines: 38 On Fri, Jul 3, 2015 at 11:03 AM, Russell King - ARM Linux wrote: > On Wed, Jul 01, 2015 at 12:12:51PM +0100, Catalin Marinas wrote: >> On Tue, Jun 30, 2015 at 11:29:06PM +0200, Lorenzo Nava wrote: >> > This patch allows the use of CMA for DMA coherent memory allocation. >> > At the moment if the input parameter "is_coherent" is set to true >> > the allocation is not made using the CMA, which I think is not the >> > desired behaviour. >> > >> > Signed-off-by: Lorenzo Nava >> > Reviewed-by: Catalin Marinas >> >> If Russell doesn't have any objections, you can send the patch to >> his patch system. See here for more information: > > I'm left wondering whether this patch is really want Lorenzo wants. > From my reading of it, while this has the effect of allocating from > CMA for coherent devices, it's no different from the non-coherent > case, because by calling __alloc_from_contiguous(), we end up > remapping the allocated memory, removing the cacheability status > from the allocated pages. > > This brings up an interesting point: presumably, it's been tested, and > people are happy with the performance it's giving, inspite of it not > returning cacheable memory... or maybe it hasn't been tested that much? > As Catalin correctly pointed out, I always consider that this patch: > -- > FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up > according to speedtest.net. -- 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/