From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7BF91C2BBD1 for ; Mon, 14 Sep 2020 21:45:00 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 24B30208DB for ; Mon, 14 Sep 2020 21:45:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="tylQD8p+" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 24B30208DB Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:Mime-Version:References:In-Reply-To:Date:To:From: Subject:Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=TDJcHhNnSMtba2Lz44jo8YruuXfyNW4MLw35XWnTT7g=; b=tylQD8p+ssdagm2zwfjbVehOI VfPVsgWgXL0QV4v8F+KfIosWV5Et+ZItrbSjW7ihTB0nJTIw3olNAqxGKjcl2Qqamj79hQHkDpC1c 3u0Og7wU9TqnfZ1dS/GfEUzLthGf5uelco+BVcItTek/Lrf3aYJxqQ7FsNuEgfVNeNKvUa6lJ6rG3 AUEKLzwqXx/HeaUMG+dyyUFdyDttmddJEGBQFsMQzqKzdO/SPG7QffwHaOQX/24ZWeS5HykCwynA/ bSh98ym07dvLriBEHcziV2ce7kyTOx+wOr0jS2Ir+NwNZRtSno6PJ6FcjiHB3djdiq1AxtWTjpsBG Gb6u19Klw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kHwFl-0002DM-AD; Mon, 14 Sep 2020 21:43:13 +0000 Received: from kernel.crashing.org ([76.164.61.194]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kHwFe-0002BI-E7 for linux-arm-kernel@lists.infradead.org; Mon, 14 Sep 2020 21:43:07 +0000 Received: from localhost (gate.crashing.org [63.228.1.57]) (authenticated bits=0) by kernel.crashing.org (8.14.7/8.14.7) with ESMTP id 08ELgi5Q004156 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Mon, 14 Sep 2020 16:42:48 -0500 Message-ID: <375c478593945a416f3180c3773bcb5240d2e36c.camel@kernel.crashing.org> Subject: Re: [PATCH] arm64: Enable PCI write-combine resources under sysfs From: Benjamin Herrenschmidt To: Jason Gunthorpe , Clint Sbisa Date: Tue, 15 Sep 2020 07:42:43 +1000 In-Reply-To: <20200914143819.GC904879@nvidia.com> References: <20200910094600.GA22840@e121166-lin.cambridge.arm.com> <20200910123758.GC904879@nvidia.com> <20200910151721.GA25809@e121166-lin.cambridge.arm.com> <20200910171033.GG904879@nvidia.com> <44acc22377958a57c738f5139c5b5df2841c2544.camel@kernel.crashing.org> <20200910232938.GJ904879@nvidia.com> <3110e00a1f4df7b7359ba4f2b7f86a35aa47405e.camel@kernel.crashing.org> <20200911214225.hml2wbbq2rofn4re@amazon.com> <20200914141726.GA904879@nvidia.com> <20200914142406.k44zrnp2wdsandsp@amazon.com> <20200914143819.GC904879@nvidia.com> X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.2 Mime-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200914_174306_685557_B80032E1 X-CRM114-Status: GOOD ( 21.92 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Lorenzo Pieralisi , Leon Romanovsky , linux-pci@vger.kernel.org, Bjorn Helgaas , catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 2020-09-14 at 11:38 -0300, Jason Gunthorpe wrote: > On Mon, Sep 14, 2020 at 02:24:06PM +0000, Clint Sbisa wrote: > > On Mon, Sep 14, 2020 at 11:17:26AM -0300, Jason Gunthorpe wrote: > > > On Fri, Sep 11, 2020 at 09:42:25PM +0000, Clint Sbisa wrote: > > > > > > > There's no DMA involved with this BAR-- the driver writes a > > > > portion of the > > > > packet contents in addition to the descriptors, which generally > > > > increases the > > > > number of TLPs if write-combine isn't used. Furthermore, this > > > > BAR is only used > > > > for writes and never for reads. > > > > > > You use DPDK without DMA? How does receive work? > > > > That was not worded well. DMA is used, but the first X bytes of the > > packet are > > written directly to this BAR instead of being DMA'd-- the rest of > > the data is > > DMA'd. > > which is back to my original question, how do you do DMA using > /sys/xx/resources? Why not use VFIO like everything else? Note: All this doesnt' change the fact that sys/xx/resources_wc exists for other archs and I see no reasons so far not to have it on ARM... Cheers, Ben. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel