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

Hi Dmitry,

On Tue Sep 8, 2026 at 3:28 PM CEST, Dmitry Baryshkov wrote:

On Mon, Aug 24, 2026 at 12:04:57PM +0200, Luca Weiss wrote:

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Hi Dmitry,

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

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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?

I was mostly using kmscube, but I can try running the CTS once I get
back to it, sorry for the delays.

Yeah, kmscube doesn't even work for me.

Bootup works to a tty with screen on (mdss doesn't seem to have any
problems for me), but then as soon as I run kmscube the device shows a
few errors on the tty0 on the screen (USB stops working apparently since
my "dmesg -w" doesn't show anything) and a few seconds later the device
reboots.

dmesg: https://public.lucaweiss.eu/tmp/fp2-iommu-dmesg.txt

The SoC in my device should be MSM8974PRO-AA (a.k.a. MSM8974AB-AA).

I know there are some differences for some bits between MSM8974
(Snapdragon 800) and MSM8974PRO (Snapdragon 801), which variant do you
have? Maybe that's relevant, also since downstream splits devicetree
based on 8974 and 8974pro.

Regards
Luca