linux-kernel - Re: [PATCH v7 1/3] iommu/arm-smmu: add NVIDIA implementation for dual ARM MMU-500 usage

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Date:   Tue, 30 Jun 2020 11:23:30 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Krishna Reddy <vdumpa@...dia.com>,
        Nicolin Chen <nicoleotsuka@...il.com>
CC:     "joro@...tes.org" <joro@...tes.org>,
        "will@...nel.org" <will@...nel.org>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        Thierry Reding <treding@...dia.com>,
        "Yu-Huan Hsu" <YHsu@...dia.com>, Sachin Nikam <Snikam@...dia.com>,
        Pritesh Raithatha <praithatha@...dia.com>,
        Timo Alho <talho@...dia.com>,
        Bitan Biswas <bbiswas@...dia.com>,
        Mikko Perttunen <mperttunen@...dia.com>,
        Nicolin Chen <nicolinc@...dia.com>,
        Bryan Huntsman <bhuntsman@...dia.com>
Subject: Re: [PATCH v7 1/3] iommu/arm-smmu: add NVIDIA implementation for dual
 ARM MMU-500 usage


On 29/06/2020 23:49, Krishna Reddy wrote:
>>> +     if (!nvidia_smmu->bases[0])
>>> +             nvidia_smmu->bases[0] = smmu->base;
>>> +
>>> +     return nvidia_smmu->bases[inst] + (page << smmu->pgshift); }
> 
>> Not critical -- just a nit: why not put the bases[0] in init()?
> 
> smmu->base is not available during nvidia_smmu_impl_init() call. It is set afterwards in arm-smmu.c.
> It can't be avoided without changing the devm_ioremap() and impl_init() call order in arm-smmu.c.


Why don't we move the call to devm_ioremap_resource() to before
arm_smmu_impl_init() in arm_smmu_device_probe()? From a quick look I
don't see why we cannot do this and seems better than what we are
currently doing which is quite confusing and hard to understand.

Jon


-- 
nvpublic