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

[Luca Weiss]

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:
>> 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:
>> > 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).
>
>> > Note, to get display to work properly one fix is necessary, [1]
>> >
>> > [1] https://patch.msgid.link/20260809-msm8974-mmcc-fix-v1-1-50f2dcf18d2e@xxxxxxxxxxxxxxxx
>> 
>> 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@xxxxxxxxxxxxxxxx
>
>> 
>> ~ # 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?