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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C79D6C43334 for ; Wed, 15 Jun 2022 17:49:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=I/Jc7u/PGHgSvvdo+vwz8p/Ut6GehVI7rxv8QE5EhMs=; b=A7zDc4gjylFTLj ixfgUUCvR0OyiDCmz4OHxXFzN8m1C9cyzaWGYfmuGHOfox0+x4znIAs1qjrrfh4YD7I4oqiDlETId QDdNYfBou9MtfAEl1GTFnmPUZZo3vJX3k0PrAJtoT/W8XCbrbKwnjhjkkS6piOX5BShVxNOU3PZ/t 77ZKcF9eTyaNZYwYESgDSImhlp6leVowIxezTYjHj8cBGPtEruY+AW6LyGnJYCjivOF4n1Q9s11lm FgKlhADrniuLMS+iYxiBdFUKognbQ7FF4+Nma6hnMMZ9/LaJS4nJx3qbcNmB0sbJNqCrnwuNYKaWY p0v9GpTzmr8mYjWUaBYA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1o1X8r-00Fool-Js; Wed, 15 Jun 2022 17:49:21 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1o1X8o-00Fomf-SC for linux-riscv@lists.infradead.org; Wed, 15 Jun 2022 17:49:20 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id F33DE68AFE; Wed, 15 Jun 2022 19:49:10 +0200 (CEST) Date: Wed, 15 Jun 2022 19:49:10 +0200 From: Christoph Hellwig To: Heiko =?iso-8859-1?Q?St=FCbner?= Cc: Christoph Hellwig , palmer@dabbelt.com, paul.walmsley@sifive.com, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, wefu@redhat.com, guoren@kernel.org, cmuellner@linux.com, philipp.tomsich@vrull.eu, samuel@sholland.org, atishp@atishpatra.org, anup@brainfault.org, mick@ics.forth.gr, robh+dt@kernel.org, krzk+dt@kernel.org, devicetree@vger.kernel.org, drew@beagleboard.org, Atish Patra Subject: Re: [PATCH 2/3] riscv: Implement Zicbom-based cache management operations Message-ID: <20220615174910.GA26607@lst.de> References: <20220610004308.1903626-1-heiko@sntech.de> <20220610004308.1903626-3-heiko@sntech.de> <20220610055608.GA24221@lst.de> <110361853.nniJfEyVGO@diego> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <110361853.nniJfEyVGO@diego> User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220615_104919_101579_A01D0AB7 X-CRM114-Status: GOOD ( 12.53 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Wed, Jun 15, 2022 at 06:56:40PM +0200, Heiko St=FCbner wrote: > If I'm reading things correctly [0], the default for those functions > is for those to be empty - but defined in the coherent case. That's not the point. Zicbom is just an extension that allows the CPU to support managing cache state. Non-coherent DMA is just one of the use cases there are others like persistent memory. And when a CPU core supports Zicbom it might or might not have any non-coherent periphals. Or even some coherent and some non-coherent ones, something that is pretty common in arm/arm64 CPUs, where PCIe is usually cache coherent, but some other cheap periphals might not be. That is why Linux ports require the plaform (usually through DT or ACPI) to mark which devices are coherent and which ones are not. _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv