Re: [PATCH] drm/msm/dp: add .shutdown to mask HPD IRQ before system shutdown

[Dmitry Baryshkov]

On Fri, Jul 17, 2026 at 04:56:13PM +0530, Mahadevan P wrote:
> On reboot, a late DP hot-plug-detect (HPD) IRQ can fire after
> apps_smmu has already disabled translation for the display
> subsystem, causing the HPD thread to kick off a new modeset that
> drives DPU/DP hardware and DMA through a stale IOMMU mapping.
> 
> DPU's own .shutdown disables all CRTCs first, but a pending HPD IRQ
> thread wakes up afterwards, reads the DPCD, and fires an unsolicited
> hotplug event that triggers a second atomic commit turning the
> display back on -- right as the IOMMU is disabling translation:
> 
>   systemd-shutdown[1]: Rebooting.
>   msm_dpu: drm_atomic_commit: committing (shutdown disabling CRTCs)
>   arm-smmu 3da0000.iommu: disabling translation
>   msm_dpu: drm_dp_read_dpcd_caps (late HPD IRQ thread wakes up)
>   msm_dpu: drm_sysfs_connector_hotplug_event: DP-1 hotplug event
>   msm_dpu: drm_client_modeset_probe: DP-1 found preferred mode
>   msm_dpu: drm_atomic_commit: committing (unsolicited, re-enables display)
>   dpu_crtc_commit_kickoff: crtc94 first commit
>   arm-smmu 15200000.iommu: disabling translation
> 
> Mask and flush the IRQ in .shutdown so no HPD event can retrigger a
> modeset once shutdown has started.
> Reported on lemans-evk and monaco-evk during reboot stress testing.
> 
> Assisted-by: Claude:claude-sonnet-5
> Signed-off-by: Mahadevan P <mahadevan.p@xxxxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/msm/dp/dp_display.c | 9 +++++++++
>  1 file changed, 9 insertions(+)

I'd very much prefer if instead we fix the framework to stop polling and
HPD notifications on shutdown.

-- 
With best wishes
Dmitry