Re: [PATCH 00/12] iommu: qcom_iommu: implement support for instances on MSM8974

Hi Dmitry,

On Tue Aug 11, 2026 at 2:43 PM CEST, Dmitry Baryshkov wrote:

On Mon, Aug 10, 2026 at 12:16:19PM +0200, Luca Weiss wrote:

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Hi Dmitry,

Many thanks for working on this and sending this patch series!

On Sun Aug 9, 2026 at 10:15 PM CEST, Dmitry Baryshkov wrote:

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Qualcomm MSM8974 platform has five SMMU instances, used by display, GPU,
Venus, VFE (camera) and JPEG encoder. Each of them follows ARM SMMU v1
spec, however they differ from other Qualcomm platforms in the
implementation-specific registers and also in interaction with TZ.
Venus, MDP and VFE SMMUs are secured and require programming only of
CBs, while GPU and JPEG require full programming.

This series skips IOMMUs which can't be tested right now (VFE and JPEG),
and adds only MDP, GPU and Venus (although untested, it is required for
display to work) SMMU instances.

I do have a patch series (sent years ago to the mailing lists as well)
for CAMSS so I can definitely test this in the future.

Ok, let's land these first, unless VFE IOMMU blocks display on your
platform (Venus was blocking display on APQ8074 DragonBoard).

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Note, to get display to work properly one fix is necessary, [1]

[1] https://patch.msgid.link/20260809-msm8974-mmcc-fix-v1-1-50f2dcf18d2e@oss.qualcomm.com

I've applied this series on v7.2-rc7, with the extra commits between
that and linux-next for qcom_iommu.c backported so that your series
applies without conflicts.

So far I'm stuck with the GPU not being able to probe, adding some
printk's shows that in msm_iommu_new() the call for
iommu_attach_device() is failing.

[    5.971154] msm_mdp fd900100.display-controller: failed to load adreno gpu
[    5.972991] msm_mdp fd900100.display-controller: failed to bind fdb00000.gpu (ops a3xx_ops [msm]): -16
[    5.974073] msm_mdp fd900100.display-controller: adev bind failed: -16
[    5.974152] panel-s6d6fa1 fd922800.dsi.0: error -EBUSY: Failed to attach to DSI host
[    5.974230] panel-s6d6fa1 fd922800.dsi.0: probe with driver panel-s6d6fa1 failed with error -16

See the patch [1], it's picked up for 7.3

I missed replying to you, with this patch the display lights up again!

Unfortunately the GPU still seems to have issues, I don't have a log
right now (I think even SSH was dropping then with a bunch of log lines
appearing in kernel log on screen). I assume kmscube + more complex
workloads worked fine for you?

Regards
Luca

[1] https://lore.kernel.org/r/20260730-fix-qcom-smmu-v2-3-18e0daf2d836@oss.qualcomm.com (local)

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~ # dmesg | grep iommu
[    0.127014] iommu: Default domain type: Translated
[    0.127052] iommu: DMA domain TLB invalidation policy: strict mode
[    0.739899] platform fdb00000.gpu: Adding to iommu group 0
[    0.741358] qcom-iommu fdc84000.iommu: iommu sec: pgtable size: 90112
[    6.006877] platform fd900100.display-controller: Adding to iommu group 1

Have you seen any issues like this?