…er_shutdown()
drm_atomic_helper_shutdown() disables all CRTCs but leaves output
polling and IRQ-driven hot-plug detection running. 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.
drm_atomic_helper_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
drm_kms_helper_poll_fini() tears down this: it stops the output poll
worker and calls each connector's &drm_connector_helper_funcs.disable_hpd,
which for HPD-capable bridges masks the interrupt in hardware.
Reported on Qualcomm platforms such as lemans-evk and monaco-evk
during reboot stress testing.
Assisted-by: Claude:claude-sonnet-5
Link: https://lore.kernel.org/all/20260730-dpshutdown-v2-1-441fc5543bed@oss.qualcomm.com/
Signed-off-by: Mahadevan P <mahadevan.p@oss.qualcomm.com>
drm_atomic_helper_shutdown() disables all CRTCs but leaves output polling and IRQ-driven hot-plug detection running. 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.
drm_atomic_helper_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
drm_kms_helper_poll_fini() tears down this: it stops the output poll worker and calls each connector's &drm_connector_helper_funcs.disable_hpd, which for HPD-capable bridges masks the interrupt in hardware.
Reported on Qualcomm platforms such as lemans-evk and monaco-evk during reboot stress testing.
Assisted-by: Claude:claude-sonnet-5
Link: https://lore.kernel.org/r/20260717-dpshutdown-v1-1-b062c2f7dfb1@oss.qualcomm.com
CRs-Fixed: 4573119