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Subject: Re: [PATCH v3 3/3] iommu/tegra-smmu: Add PCI support
To:     Nicolin Chen <nicoleotsuka@gmail.com>, thierry.reding@gmail.com,
        joro@8bytes.org, krzk@kernel.org
Cc:     vdumpa@nvidia.com, jonathanh@nvidia.com,
        linux-tegra@vger.kernel.org, iommu@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
References: <20200930084258.25493-1-nicoleotsuka@gmail.com>
 <20200930084258.25493-4-nicoleotsuka@gmail.com>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <0a308ee8-abf7-97e4-9814-2156ee56fe8b@gmail.com>
Date:   Wed, 30 Sep 2020 17:53:20 +0300
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...
> +#ifdef CONFIG_PCI
> +	if (!iommu_present(&pci_bus_type)) {


In the previous reply you said that you're borrowing this check from the
arm-smmu driver, but arm-smmu also has a similar check for
platform_bus_type, while Tegra SMMU driver doesn't have it. Hence I'm
objecting the necessity of having this check.

Please give a rationale for having this check in the code. And please
note that cargo cult isn't a rationale to me.