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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jLRaN-00039N-Ez; Mon, 06 Apr 2020 13:14:43 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jLRaK-00038M-7y for linux-arm-kernel@lists.infradead.org; Mon, 06 Apr 2020 13:14:41 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 1707C31B; Mon, 6 Apr 2020 06:14:37 -0700 (PDT) Received: from red-moon.cambridge.arm.com (unknown [10.57.29.239]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id EC20F3F52E; Mon, 6 Apr 2020 06:14:35 -0700 (PDT) Date: Mon, 6 Apr 2020 14:14:32 +0100 From: Lorenzo Pieralisi To: Ard Biesheuvel Subject: Re: [PATCH] arm64: iort: take _DMA methods into account for named components Message-ID: <20200406131432.GC4650@red-moon.cambridge.arm.com> References: <20200404073047.17898-1-ardb@kernel.org> <20200406110401.GA4650@red-moon.cambridge.arm.com> <20200406113235.GB4650@red-moon.cambridge.arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200406_061440_327319_1B12DFEA X-CRM114-Status: GOOD ( 16.85 ) 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: Catalin Marinas , Will Deacon , robin.murphy@arm.com, Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Apr 06, 2020 at 01:59:07PM +0200, Ard Biesheuvel wrote: > On Mon, 6 Apr 2020 at 13:32, Lorenzo Pieralisi > wrote: > > > > On Mon, Apr 06, 2020 at 01:16:15PM +0200, Ard Biesheuvel wrote: > > > On Mon, 6 Apr 2020 at 13:04, Lorenzo Pieralisi > > > wrote: > > > > > > > > On Sat, Apr 04, 2020 at 09:30:47AM +0200, Ard Biesheuvel wrote: > > > > > Where IORT nodes for named components can describe simple DMA limits > > > > > expressed as the number of address bits a device can driver, _DMA methods > > > > > in AML can express more complex topologies, involving DMA translation in > > > > > particular. > > > > > > > > > > Currently, we only take this _DMA method into account if it appears on a > > > > > ACPI device node describing a PCIe root complex, but it is perfectly > > > > > acceptable to attach them to named components as well, so let's ensure > > > > > we take them into account in those cases too. > > > > > > > > ACPI spec v6.3, 6.2.4 _DMA: > > > > > > > > "_DMA is only defined under devices that represent buses" > > > > > > > > > > Sure. But ACPI0004 module devices are also bus nodes, so that > > > statement does not exclude named components that are defined under > > > such a module device. > > > > Yes. _DMA is valid only if a _CRS is present, ACPI0004 does not seem > > to _require_ a _CRS to be considered valid. > > > > How is that relevant? Any node that has a _DMA must have a _CRS as > well. Some nodes that don't have a _DMA may not have a _CRS either. > But that does not disqualify a ACPI0004 that *does* have both from > being considered a bus node, no? Or is that not what you are saying? I am just trying to prevent firmware developers from adding ACPI0004 nodes with *just* a _DMA object (because the _CRS is optional) which will become unusable in OS context (where we do check the _CRS presence), that's all I am saying. Just trying to make specs foolproof :) Thanks, Lorenzo _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel