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[209.132.180.67]) by mx.google.com with ESMTP id j1si6238994pfr.52.2019.08.30.10.46.29; Fri, 30 Aug 2019 10:46:45 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728067AbfH3Rpn (ORCPT + 99 others); Fri, 30 Aug 2019 13:45:43 -0400 Received: from foss.arm.com ([217.140.110.172]:35696 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727791AbfH3Rpm (ORCPT ); Fri, 30 Aug 2019 13:45:42 -0400 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 170BF337; Fri, 30 Aug 2019 10:45:42 -0700 (PDT) Received: from [10.1.197.57] (e110467-lin.cambridge.arm.com [10.1.197.57]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 719A83F718; Fri, 30 Aug 2019 10:45:37 -0700 (PDT) Subject: Re: [PATCH 6/7] arm64: tegra: Add DT node for T194 SMMU To: Krishna Reddy Cc: Sachin Nikam , "Thomas Zeng (SW-TEGRA)" , Juha Tukkinen , Mikko Perttunen , Pritesh Raithatha , "iommu@lists.linux-foundation.org" , "linux-kernel@vger.kernel.org" , Timo Alho , Yu-Huan Hsu , "linux-tegra@vger.kernel.org" , Thierry Reding , Alexander Van Brunt , "linux-arm-kernel@lists.infradead.org" , "will.deacon@arm.com" , "joro@8bytes.org" References: <1567118827-26358-1-git-send-email-vdumpa@nvidia.com> <1567118827-26358-7-git-send-email-vdumpa@nvidia.com> From: Robin Murphy Message-ID: Date: Fri, 30 Aug 2019 18:45:34 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 30/08/2019 18:25, Krishna Reddy wrote: >>> + #global-interrupts = <1>; > >> Shouldn't that be 3? > > Interrupt line is shared between global and all context faults for each SMMU instance. > Nvidia implementation checks for both Global and context faults on each interrupt to an SMMU instance. > It can be either 1 or 3. If we make it 3, we need to add two more irq entries in node for context faults. The number of global interrupts has never been related to the number of context interrupts :/ > In the future, we can update arm-smmu.c to support shared interrupt line between global and all context faults. Clearly you have one combined interrupt output per SMMU - describing those as one global interrupt and the first two context bank interrupts respectively makes far less sense than calling them 3 global interrupts, not least because the latter is strictly true. Yes, the binding prevents us from describing the context bank interrupts for more than one instance, but at that point the fact that it *is* the combined output saves us - because the driver is aware of this specific integration it knows it can just register the "secondary" global interrupts as "secondary" context interrupts too. If we had separate IRQ lines per context bank per instance, then we'd have a really big problem and might have to redefine the binding, but as it is it happens to work out pretty neatly. Robin.