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From: Jon Hunter <jonathanh@nvidia.com>
To: Krishna Reddy <vdumpa@nvidia.com>, Robin Murphy <robin.murphy@arm.com>
Cc: Sachin Nikam <Snikam@nvidia.com>,
	"nicoleotsuka@gmail.com" <nicoleotsuka@gmail.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 v8 2/3] dt-bindings: arm-smmu: Add binding for Tegra194 SMMU
Date: Wed, 1 Jul 2020 19:47:36 +0100	[thread overview]
Message-ID: <0d4f46d6-6a4e-bca0-bcf3-0e22a950e57b@nvidia.com> (raw)
In-Reply-To: <BYAPR12MB28222D6ADEBA966AA27FA9ECB36C0@BYAPR12MB2822.namprd12.prod.outlook.com>


On 01/07/2020 19:28, Krishna Reddy wrote:
>>> +      - description: NVIDIA SoCs that use more than one "arm,mmu-500"
>> Hmm, there must be a better way to word that to express that it only applies to the sets of SMMUs that must be programmed identically, and not any other independent MMU-500s that might also happen to be in the same SoC.
> 
> Let me reword it to "NVIDIA SoCs that must program multiple MMU-500s identically".
> 
>>> +        items:
>>> +          - enum:
>>> +              - nvdia,tegra194-smmu
>>> +          - const: arm,mmu-500
> 
>> Is the fallback compatible appropriate here? If software treats this as a standard MMU-500 it will only program the first instance (because the second isn't presented as a separate MMU-500) - is there any way that isn't going to blow up?
> 
> When compatible is set to both nvidia,tegra194-smmu and arm,mmu-500, implementation override ensure that both instances are programmed. Isn't it? I am not sure I follow your comment fully.

The problem is, if for some reason someone had a Tegra194, but only set
the compatible string to 'arm,mmu-500' it would assume that it was a
normal arm,mmu-500 and only one instance would be programmed. We always
want at least 2 of the 3 instances programmed and so we should only
match 'nvidia,tegra194-smmu'. In fact, I think that we also need to
update the arm_smmu_of_match table to add 'nvidia,tegra194-smmu' with
the data set to &arm_mmu500.

Jon

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nvpublic
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  reply	other threads:[~2020-07-01 18:47 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-30  0:10 [PATCH v8 0/3] Nvidia Arm SMMUv2 Implementation Krishna Reddy
2020-06-30  0:10 ` [PATCH v8 1/3] iommu/arm-smmu: add NVIDIA implementation for dual ARM MMU-500 usage Krishna Reddy
2020-06-30  0:16   ` Nicolin Chen
2020-06-30  5:54   ` Pritesh Raithatha
2020-06-30  8:19   ` Jon Hunter
2020-06-30 14:53     ` Robin Murphy
2020-06-30 15:17       ` Jon Hunter
2020-07-01 18:18       ` Krishna Reddy
2020-07-01 18:56         ` Robin Murphy
2020-07-01 19:12           ` Krishna Reddy
2020-06-30 17:04     ` Krishna Reddy
2020-06-30 10:17   ` Jon Hunter
2020-06-30 16:23     ` Krishna Reddy
2020-06-30 16:32       ` Jon Hunter
2020-06-30 16:44         ` Jon Hunter
2020-06-30 17:16           ` Krishna Reddy
2020-06-30 19:03             ` Jon Hunter
2020-06-30 20:21               ` Krishna Reddy
2020-06-30  0:10 ` [PATCH v8 2/3] dt-bindings: arm-smmu: Add binding for Tegra194 SMMU Krishna Reddy
2020-06-30  6:01   ` Pritesh Raithatha
2020-06-30  8:21   ` Jon Hunter
2020-06-30 12:27   ` Robin Murphy
2020-07-01 18:28     ` Krishna Reddy
2020-07-01 18:47       ` Jon Hunter [this message]
2020-07-01 19:00         ` Krishna Reddy
2020-07-01 19:31           ` Jon Hunter
2020-07-01 19:39             ` Krishna Reddy
2020-07-02 16:05               ` Robin Murphy
2020-07-01 19:03         ` Robin Murphy
2020-06-30  0:10 ` [PATCH v8 3/3] iommu/arm-smmu: Add global/context fault implementation hooks Krishna Reddy
2020-06-30  0:19   ` Nicolin Chen
2020-06-30  5:58   ` Pritesh Raithatha
2020-06-30  8:37   ` Jon Hunter
2020-06-30 12:13     ` Robin Murphy
2020-06-30 12:42       ` Jon Hunter
2020-07-01 18:48       ` Krishna Reddy
2020-07-01 19:14         ` Robin Murphy
2020-07-01 19:22           ` Krishna Reddy

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