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From: Robin Murphy <robin.murphy@arm.com>
To: Jon Hunter <jonathanh@nvidia.com>,
	Krishna Reddy <vdumpa@nvidia.com>,
	Nicolin Chen <nicoleotsuka@gmail.com>
Cc: Sachin Nikam <Snikam@nvidia.com>,
	Mikko Perttunen <mperttunen@nvidia.com>,
	Bryan Huntsman <bhuntsman@nvidia.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Pritesh Raithatha <praithatha@nvidia.com>,
	Timo Alho <talho@nvidia.com>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	Nicolin Chen <nicolinc@nvidia.com>,
	"linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>,
	Yu-Huan Hsu <YHsu@nvidia.com>,
	Thierry Reding <treding@nvidia.com>,
	"will@kernel.org" <will@kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	Bitan Biswas <bbiswas@nvidia.com>
Subject: Re: [PATCH v7 1/3] iommu/arm-smmu: add NVIDIA implementation for dual ARM MMU-500 usage
Date: Tue, 30 Jun 2020 11:46:39 +0100	[thread overview]
Message-ID: <be484deb-efc9-72cd-f83f-e11713539023@arm.com> (raw)
In-Reply-To: <b353b3f0-ee7f-f777-4d38-c595bc990564@nvidia.com>

On 2020-06-30 11:23, Jon Hunter wrote:
> 
> 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.

Yeah, I don't see any problem with adding a patch to do that. 
impl_init() does need to happen before generic probe starts touching any 
registers, but it wouldn't have any business overriding the platform 
resources or anything that would affect the ioremap itself. Plus it's 
reasonable that some theoretical future impl_init() might want to check 
registers for, say, a particular hardware revision, so having 
smmmu->base mapped and valid at that point would be no bad thing.

Robin.
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  reply	other threads:[~2020-06-30 10:46 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-29  2:28 [PATCH v7 0/3] Nvidia Arm SMMUv2 Implementation Krishna Reddy
2020-06-29  2:28 ` [PATCH v7 1/3] iommu/arm-smmu: add NVIDIA implementation for dual ARM MMU-500 usage Krishna Reddy
2020-06-29 21:51   ` Nicolin Chen
2020-06-29 22:49     ` Krishna Reddy
2020-06-29 23:52       ` Nicolin Chen
2020-06-30 10:23       ` Jon Hunter
2020-06-30 10:46         ` Robin Murphy [this message]
2020-06-29  2:28 ` [PATCH v7 2/3] dt-bindings: arm-smmu: Add binding for Tegra194 SMMU Krishna Reddy
2020-06-29  2:28 ` [PATCH v7 3/3] iommu/arm-smmu: Add global/context fault implementation hooks Krishna Reddy
2020-06-29 22:38   ` Nicolin Chen
2020-06-29 23:28     ` Krishna Reddy

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