Re: [PATCH 03/16] dt-bindings: ehci/ohci: Allow iommus property (fixed subject line)

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On 05/05/2020 18:51, Robin Murphy wrote:
> On 2020-05-05 5:51 pm, Andre Przywara wrote:
>> Date: Mon, 4 May 2020 12:43:18 +0100
>> Subject: [PATCH 03/16] dt-bindings: ehci/ohci: Allow iommus property
>>
>> A OHCI/EHCI controller could be behind an IOMMU, in which case an iommus
>> property assigns the stream ID for this device.
> 
> Hmm, pretty much any DMA master device could be behind an IOMMU, and in
> a way that's basically entirely irrelevant to the device itself (and
> thus the consumer of its binding). Is there a better way we can handle
> this than repeating such "semi-standard" properties in individual
> bindings for ever more?

I was asking exactly the same question to Rob.
Indeed this is more of a parent bus property, if at all, and individual
drivers are not even aware of this.
But what is a device property is the number of device IDs that the
device uses and that would need to be translated into stream IDs.

So I think this is merely saying: just a single device ID.

And no, we couldn't come up with some more generic solution (yet). I
think a similar problem comes up with power-domains and other properties
handled by code in drivers/of.

Cheers,
Andre

> 
> Robin.
> 
>> Allow that property in the DT bindings to fix a complaint about the
>> Arm Juno
>> board's DTS file.
>>
>> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
>> ---
>>   Documentation/devicetree/bindings/usb/generic-ehci.yaml | 3 +++
>>   Documentation/devicetree/bindings/usb/generic-ohci.yaml | 3 +++
>>   2 files changed, 6 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/usb/generic-ehci.yaml
>> b/Documentation/devicetree/bindings/usb/generic-ehci.yaml
>> index 10edd05872ea..20664c28bfb2 100644
>> --- a/Documentation/devicetree/bindings/usb/generic-ehci.yaml
>> +++ b/Documentation/devicetree/bindings/usb/generic-ehci.yaml
>> @@ -74,6 +74,9 @@ properties:
>>     phy-names:
>>       const: usb
>>   +  iommus:
>> +    maxItems: 1
>> +
>>   required:
>>     - compatible
>>     - reg
>> diff --git a/Documentation/devicetree/bindings/usb/generic-ohci.yaml
>> b/Documentation/devicetree/bindings/usb/generic-ohci.yaml
>> index bcffec1f1341..ff6c04cde695 100644
>> --- a/Documentation/devicetree/bindings/usb/generic-ohci.yaml
>> +++ b/Documentation/devicetree/bindings/usb/generic-ohci.yaml
>> @@ -73,6 +73,9 @@ properties:
>>     phy-names:
>>       const: usb
>>   +  iommus:
>> +    maxItems: 1
>> +
>>   required:
>>     - compatible
>>     - reg
>>




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