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

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Message-ID: <7ba3953a-166f-4c67-8f54-666b0c488b12@kernel.org>
Date: Thu, 9 Oct 2025 09:38:04 +0100
From: Bryan O'Donoghue <bod@...nel.org>
To: Krzysztof Kozlowski <krzk@...nel.org>,
 Bryan O'Donoghue <bryan.odonoghue@...aro.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>,
 Vikash Garodia <quic_vgarodia@...cinc.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 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

The xls for these mappings runs to a few hundred lines.

Seems to me like a good argument - at least for the qcom iommus to add a 
cell entry and then teach the generic iommu code about it.

---
bod