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 72C7EC433E2 for ; Mon, 14 Sep 2020 21:44:36 +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 285FC20759 for ; Mon, 14 Sep 2020 21:44:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="sMqTCeD5" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 285FC20759 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=6dVzxO9Mun0sc81HHMysZ2aVolQC0kt0T38lFkn1VSo=; b=sMqTCeD57VQZ7BS2MCnOC7ZYF BNNy2V9ffw24ZhGJQ2QQSYXrI3D6OB9h9f6TNQrfwdizXmsmUWyLdDpxhvZ4j620zNYfAYoyI8k02 H4LqlpKe1i3NmrZh5eHniim8qgvO9NzSMx4AevgE7Dj815DG1rpdqFCpA6WWCLxIX2kFDhNjofDQh gDwDyto6Huypc6D7SIQXWMU4hJsVOJjvhqKwVazk1kstmofw58GIgUzvpaZ6XhJSTX9CGuyqeckmD UHVZtTvJLUuUIb0tvm1xl4Xf6MD0tSo27TTyIA1v4UXt6NQaYamfJkqspJGhcf6dExuknSReDFp0d dxWlkHbQg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kHwFB-00029A-0k; Mon, 14 Sep 2020 21:42:37 +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 1kHwF8-00028h-6L for linux-arm-kernel@lists.infradead.org; Mon, 14 Sep 2020 21:42:35 +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 08ELfn7G004136 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Mon, 14 Sep 2020 16:41:53 -0500 Message-ID: <2162790a078034604779afd49bb84ef3e21d9ba4.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 07:41:48 +1000 In-Reply-To: <20200914141726.GA904879@nvidia.com> References: <20200903110844.GB11284@e121166-lin.cambridge.arm.com> <28d333afc73bd854390f8c39691a735040ba5b39.camel@kernel.crashing.org> <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> 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_174234_390368_E25A0E70 X-CRM114-Status: GOOD ( 17.17 ) 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 11:17 -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? > > > As Jason noted in the other reply to this email, the Linux ENA > > driver makes use > > of WC by using devm_ioremap_wc(). > > As Ben noted we don't have kernel accessors to make this portable or > safe :( Well.. to be frank it does work "well enough" for simple cases like frame buffers :-) Cheers Ben. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel