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

[Dmitry Baryshkov]

On Thu, 10 Sept 2026 at 13:38, Luca Weiss <luca.weiss at fairphone.com> wrote:
>
> 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:
> >> 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@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.

Interesting. I wonder if it's TZ tripping on the VFE IOMMU.

>
> 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.

Mine is APQ8074, not sure if there were revisions.

-- 
With best wishes
Dmitry