linux-kernel - [PATCH RFC 0/2] Add GPU support to MSM8953 SoC

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Date: Thu, 25 Jan 2024 22:56:24 +0100
From: Luca Weiss <luca@...tu.xyz>
To: ~postmarketos/upstreaming@...ts.sr.ht, phone-devel@...r.kernel.org, 
 Bjorn Andersson <andersson@...nel.org>, 
 Konrad Dybcio <konrad.dybcio@...aro.org>, Rob Herring <robh+dt@...nel.org>, 
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, 
 Conor Dooley <conor+dt@...nel.org>, 
 Vladimir Lypak <vladimir.lypak@...il.com>
Cc: linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Luca Weiss <luca@...tu.xyz>
Subject: [PATCH RFC 0/2] Add GPU support to MSM8953 SoC

Add the GPU IOMMU and GPU nodes to the msm8953 dtsi so GPU can work.

First of all, functionally this series looks fine, tested on
sdm632-fairphone-fp3.

Secondly and the reason this is marked RFC for now is basically just dt
bindings check fail, and some questions regarding IOMMU compatible.

Basically I'm unsure what compatible (or even driver) IOMMU should use.
qcom,msm-iommu-v2 is now in the patchset which seems to be okay, and
also should handle the gfx3d_secure secure context correctly. Apart from
some special handling there qcom,msm-iommu-v1 compatible is equivalent
on the driver side.

Currently the dt bindings say qcom,msm8953-iommu should be followed by
qcom,msm-iommu-v1 which is the case for apps_iommu. But if we use
qcom,msm-iommu-v2 for gpu_iommu then we can't re-use the same
qcom,msm8953-iommu I think.

Possible solutions:
1. Switch apps_iommu to use qcom,msm-iommu-v2 in dts & bindings? Since
   there's basically no special handling for either in the driver I
   don't forsee any problems. Then we can also use -v2 for gpu_iommu no
   problem.
2. Use qcom,msm-iommu-v1 for gpu_iommu? From some testing it also seems
   to work, I guess because the secure context is never used?
3. Use arm_smmu driver for gpu_iommu? Vladimir Lypak has suggested that,
   but that would at least need some more patching to work on msm8953.
   I probably don't have the motivation to take this on myself. Also
   what benefit would it bring?

Hope I haven't rambled too long here and it's somewhat understandable.

Please let me know what you think, which direction we can take to
resolve this.

(Also GPU clock-names dt-schema check fails but that seems to be the
 case on more a5xx GPUs also)

Signed-off-by: Luca Weiss <luca@...tu.xyz>
---
Vladimir Lypak (2):
      arm64: dts: qcom: msm8953: Add GPU IOMMU
      arm64: dts: qcom: msm8953: Add GPU

 arch/arm64/boot/dts/qcom/msm8953.dtsi            | 146 +++++++++++++++++++++++
 arch/arm64/boot/dts/qcom/sdm450-motorola-ali.dts |   2 +-
 arch/arm64/boot/dts/qcom/sdm450.dtsi             |  14 +++
 arch/arm64/boot/dts/qcom/sdm632.dtsi             |   8 ++
 4 files changed, 169 insertions(+), 1 deletion(-)
---
base-commit: 0e21aa976976d5fba8cd1f8f64bcce49beb5f895
change-id: 20231212-msm8953-gpu-4c085365f594

Best regards,
-- 
Luca Weiss <luca@...tu.xyz>