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[109.252.91.252]) by smtp.googlemail.com with ESMTPSA id w17sm571611lfn.55.2020.10.02.13.12.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 02 Oct 2020 13:12:19 -0700 (PDT) Subject: Re: [PATCH v4 1/3] iommu/tegra-smmu: Use fwspec in tegra_smmu_(de)attach_dev To: Nicolin Chen Cc: thierry.reding@gmail.com, joro@8bytes.org, vdumpa@nvidia.com, jonathanh@nvidia.com, linux-tegra@vger.kernel.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <20201002060807.32138-1-nicoleotsuka@gmail.com> <20201002060807.32138-2-nicoleotsuka@gmail.com> <20201002194508.GD29706@Asurada-Nvidia> From: Dmitry Osipenko Message-ID: Date: Fri, 2 Oct 2020 23:12:18 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201002194508.GD29706@Asurada-Nvidia> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-tegra@vger.kernel.org 02.10.2020 22:45, Nicolin Chen пишет: > On Fri, Oct 02, 2020 at 05:41:50PM +0300, Dmitry Osipenko wrote: >> 02.10.2020 09:08, Nicolin Chen пишет: >>> static int tegra_smmu_attach_dev(struct iommu_domain *domain, >>> struct device *dev) >>> { >>> + struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev); >>> struct tegra_smmu *smmu = dev_iommu_priv_get(dev); >>> struct tegra_smmu_as *as = to_smmu_as(domain); >>> - struct device_node *np = dev->of_node; >>> - struct of_phandle_args args; >>> unsigned int index = 0; >>> int err = 0; >>> >>> - while (!of_parse_phandle_with_args(np, "iommus", "#iommu-cells", index, >>> - &args)) { >>> - unsigned int swgroup = args.args[0]; >>> - >>> - if (args.np != smmu->dev->of_node) { >>> - of_node_put(args.np); >>> - continue; >>> - } >>> - >>> - of_node_put(args.np); >>> + if (!fwspec) >>> + return -ENOENT; >> >> Could the !fwspec ever be true here as well? > > There are multiple callers of this function. It's really not that > straightforward to track every one of them. So I'd rather have it > here as other iommu drivers do. We are human beings, so we could > have missed something somewhere, especially callers are not from > tegra-* drivers. > I'm looking at the IOMMU core and it requires device to be in IOMMU group before attach_dev() could be called. The group can't be assigned to device without the fwspec, see tegra_smmu_device_group(). Seems majority of IOMMU drivers are checking dev_iommu_priv_get() for NULL in attach_dev(), some not checking anything, some check both and only arm-smmu checks the fwspec.