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[216.228.112.22]) by smtp.gmail.com with ESMTPSA id c1sm648658pfj.219.2020.09.29.22.33.31 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Tue, 29 Sep 2020 22:33:32 -0700 (PDT) Date: Tue, 29 Sep 2020 22:28:00 -0700 From: Nicolin Chen To: Dmitry Osipenko Cc: thierry.reding@gmail.com, joro@8bytes.org, krzk@kernel.org, vdumpa@nvidia.com, jonathanh@nvidia.com, linux-tegra@vger.kernel.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/3] iommu/tegra-smmu: Add PCI support Message-ID: <20200930052759.GA31821@Asurada-Nvidia> References: <20200930003013.31289-1-nicoleotsuka@gmail.com> <20200930003013.31289-4-nicoleotsuka@gmail.com> <27b155ec-97ab-98f6-7b48-3fded875d5cc@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <27b155ec-97ab-98f6-7b48-3fded875d5cc@gmail.com> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 30, 2020 at 08:10:00AM +0300, Dmitry Osipenko wrote: > 30.09.2020 03:30, Nicolin Chen пишет: > ... > > +#ifdef CONFIG_PCI > > + if (!iommu_present(&pci_bus_type)) { > > Could you please explain why this check is needed? That's referencing what's in the arm-smmu.c file, since it does not hurt to have a check.