linux-kernel - Re: [PATCH v3 0/5] Introduce "non-pixel" sub node within iris video node

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Message-ID: <28baa5ce-c161-426a-b5df-1cd784489bb5@linaro.org>
Date: Thu, 9 Oct 2025 12:06:26 +0100
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To: Krzysztof Kozlowski <krzk@...nel.org>,
 Vikash Garodia <quic_vgarodia@...cinc.com>, Bryan O'Donoghue
 <bod@...nel.org>, Charan Teja Kalla <charan.kalla@....qualcomm.com>,
 Bryan O'Donoghue <bod.linux@...w.ie>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
 Dikshita Agarwal <quic_dikshita@...cinc.com>,
 Abhinav Kumar <abhinav.kumar@...ux.dev>,
 Mauro Carvalho Chehab <mchehab@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, linux-media@...r.kernel.org,
 linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/5] Introduce "non-pixel" sub node within iris video
 node

On 09/10/2025 11:45, Krzysztof Kozlowski wrote:
> On 09/10/2025 19:40, Vikash Garodia wrote:
>>
>> On 10/9/2025 2:41 PM, Krzysztof Kozlowski wrote:
>>> On 09/10/2025 17:38, Bryan O'Donoghue wrote:
>>>> On 09/10/2025 02:04, Krzysztof Kozlowski wrote:
>>>>>> The iommu description for this platform basically lacks the data that
>>>>>> _should_ be there -> FUNCTION_ID.
>>>>> No. The index tells that already.
>>>>
>>>> Hmm.
>>>>>> The rule is that the DT should really describe the hardware right ?
>>>>> It already does. Same as I wrote on IRC, DT already has all the
>>>>> information. Entry 0 has function ID-foo. Entry 1 has function ID-bar.
>>>>> Entry 2 has function ID-bar or whatever.
>>>>
>>>> That's the part I don't believe is true its a 1:Many relationship
>>>> between FUNCTION_ID:SIDs
>>>>
>>>> Let me check the docs...
>>>>
>>>> Here's the example I gave on IRC for lore
>>>>
>>>> SID 0x1940 maps to AC_VM_HLOS (Linux)
>>>> SID 0x1941 maps to AC_VM_CP_BITSTREAM - protected bitstream
>>>> SID 0x1945 maps to AC_WM_CP_BITSTREAM
>>>>
>>>
>>> I responded to this on IRC... Nothing proves here that 1:many cannot be
>>> done.
>>
>> Kaanapali already has 1:Many relationship for FUNCTION_ID:SIDs.
> 
> Sun is a star. How is that related? I am not going to duplicate
> arguments from IRC, especially to that pointless argument. Read again
> discussion on IRC.
> 
> Best regards,
> Krzysztof

But Krzysztof is it not the case DT should be a representation of the 
real hardware and that this takes priority over established schema.

There seems to be no other reason to keep SID in the DT and FUNCTION_ID 
in driver meta-data except the schema already says X.

There are as I count it, 189 TCU SID mappings for Hamoa.

So in the extreme case that means we have an iommu = <> for each of 
those but then need a corresponding entry in a driver to map each SID to 
its relevant FUNCTION_ID.

And do that over and over again for each new SoC.

OTOH if we extend the iommu to include FUNCTION_ID then only the DT 
changes - with the iommu setup code changing once to accommodate it.

---
bod