linux-kernel - Re: [PATCH v4 1/9] dt-bindings: host1x: Add iommu-map property

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Message-ID: <3466cb33-7f5c-7b57-85f8-387e93516432@kapsi.fi>
Date:   Wed, 2 Mar 2022 14:31:46 +0200
From:   Mikko Perttunen <cyndis@...si.fi>
To:     Robin Murphy <robin.murphy@....com>, thierry.reding@...il.com,
        jonathanh@...dia.com, joro@...tes.org, will@...nel.org,
        robh+dt@...nel.org, krzysztof.kozlowski@...onical.com
Cc:     linux-tegra@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Mikko Perttunen <mperttunen@...dia.com>
Subject: Re: [PATCH v4 1/9] dt-bindings: host1x: Add iommu-map property

On 3/1/22 20:12, Robin Murphy wrote:
> On 2022-03-01 16:14, cyndis@...si.fi wrote:
>> From: Mikko Perttunen <mperttunen@...dia.com>
>>
>> Add schema information for specifying context stream IDs. This uses
>> the standard iommu-map property.
>>
>> Signed-off-by: Mikko Perttunen <mperttunen@...dia.com>
>> ---
>> v3:
>> * New patch
>> v4:
>> * Remove memory-contexts subnode.
>> ---
>>   .../bindings/display/tegra/nvidia,tegra20-host1x.yaml        | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git 
>> a/Documentation/devicetree/bindings/display/tegra/nvidia,tegra20-host1x.yaml 
>> b/Documentation/devicetree/bindings/display/tegra/nvidia,tegra20-host1x.yaml 
>>
>> index 4fd513efb0f7..0adeb03b9e3a 100644
>> --- 
>> a/Documentation/devicetree/bindings/display/tegra/nvidia,tegra20-host1x.yaml 
>>
>> +++ 
>> b/Documentation/devicetree/bindings/display/tegra/nvidia,tegra20-host1x.yaml 
>>
>> @@ -144,6 +144,11 @@ allOf:
>>           reset-names:
>>             maxItems: 1
>> +        iommu-map:
>> +          description: Specification of stream IDs available for 
>> memory context device
>> +            use. Should be a mapping of IDs 0..n to IOMMU entries 
>> corresponding to
> 
> Nit: maybe "context IDs 0..n" for maximum possible clarity?

I left it at "IDs" since there is no "context ID" or similar concept in 
the hardware, so I thought to leave it just as a kind of an 'abstract ID 
as used in iommu-map property'.

> 
> Either way, though, I'm happy that if the simplest and most 
> straightforward approach works, then it's the best choice.

I am happy as well, this is certainly much cleaner than the mess in the 
downstream driver :)

> 
> Reviewed-by: Robin Murphy <robin.murphy@....com>
> 
> Cheers,
> Robin.

Thanks!
Mikko

> 
>> +            usable stream IDs.
>> +
>>         required:
>>           - reg-names