linux-kernel - Re: [PATCH 1/5] dt-bindings: media: qcom,sm8550-iris: add non_pixel and resv

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Message-ID: <20250627195148.GA4062030-robh@kernel.org>
Date: Fri, 27 Jun 2025 14:51:48 -0500
From: Rob Herring <robh@...nel.org>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Cc: Krzysztof Kozlowski <krzk@...nel.org>,
	Vikash Garodia <quic_vgarodia@...cinc.com>,
	Dikshita Agarwal <quic_dikshita@...cinc.com>,
	Abhinav Kumar <abhinav.kumar@...ux.dev>,
	Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
	Mauro Carvalho Chehab <mchehab@...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 1/5] dt-bindings: media: qcom,sm8550-iris: add non_pixel
 and resv_region properties

On Fri, Jun 20, 2025 at 07:27:03PM +0200, Konrad Dybcio wrote:
> On 6/20/25 8:39 AM, Krzysztof Kozlowski wrote:
> > On 20/06/2025 08:20, Vikash Garodia wrote:
> >> Existing definition limits the IOVA to an addressable range of 4GiB, and
> >> even within that range, some of the space is used by IO registers,
> >> thereby limiting the available IOVA to even lesser. Video hardware is
> >> designed to emit different stream-ID for pixel and non_pixel buffers,
> >> thereby introduce a non_pixel sub node to handle non_pixel stream-ID.
> >>
> >> With this, both iris and non_pixel device can have IOVA range of 0-4GiB
> >> individually. Certain video usecases like higher video concurrency needs
> >> IOVA higher than 4GiB.
> >>
> >> Add the "resv_region" property, which defines reserved IOVA regions that
> >> are *excluded* from addressable range. Video hardware generates
> >> different stream IDs based on the range of IOVA addresses. Thereby IOVA
> >> addresses for firmware and data buffers need to be non overlapping. For
> >> ex. 0x0-0x25800000 address range is reserved for firmware stream-ID,
> >> while non_pixel (bitstream ) stream-ID can be generated by hardware only
> >> when bitstream buffers IOVA address is from 0x25800000-0xe0000000.
> >>
> >> Signed-off-by: Vikash Garodia <quic_vgarodia@...cinc.com>
> >> ---
> >>  .../bindings/media/qcom,sm8550-iris.yaml           | 35 ++++++++++++++++++++++
> >>  1 file changed, 35 insertions(+)
> >>
> >> diff --git a/Documentation/devicetree/bindings/media/qcom,sm8550-iris.yaml b/Documentation/devicetree/bindings/media/qcom,sm8550-iris.yaml
> >> index c79bf2101812d83b99704f38b7348a9f728dff44..a1e83bae3c36f3a4c58b212ef457905e38091b97 100644
> >> --- a/Documentation/devicetree/bindings/media/qcom,sm8550-iris.yaml
> >> +++ b/Documentation/devicetree/bindings/media/qcom,sm8550-iris.yaml
> >> @@ -65,10 +65,45 @@ properties:
> >>        - const: core
> >>  
> >>    iommus:
> >> +    minItems: 1
> > 
> > As discussed in other patchset, this needs clear explanation, so
> > imperfect patch won't be used in future discussions as argument to take
> > more of such things.
> > 
> >>      maxItems: 2
> >>  
> >>    dma-coherent: true
> >>  
> >> +  resv_region:
> > 
> > DTS coding style. Anyway, regions go with memory-region bindings. Use that.
> 
> On a tangent, FWIW this is a discussion related to this patchset that
> never got much attention:
> 
> https://lore.kernel.org/linux-devicetree/9439182e-3338-4d57-aa02-b621bc9498a3@oss.qualcomm.com/

Send !patches to devicetree-spec if you want any chance of it being 
seen. If it is not a patch in PW from the firehose that's the 
devicetree list, then I likely never read it. 

But I don't have any clue how iommu-addresses works to give guidance. 
I'd propose something that works for you if you really want some 
discussion.

Rob