We have noticed these kernel warnings on APQ 8016 SBC (dragonboard 410c ) running stable rc 5.5, 5.4 branches and linux mainline and linux-next master branches. This warning started happening from linux mainline 5.3 onwards (2019-08-29) [ 5.488128] ------------[ cut here ]------------ [ 5.488161] WARNING: CPU: 3 PID: 221 at drivers/iommu/qcom_iommu.c:348 qcom_iommu_domain_free+0x5c/0x70 [ 5.491817] Modules linked in: crct10dif_ce(+) adv7511(+) cec msm(+) mdt_loader drm_kms_helper drm fuse [ 5.491842] CPU: 3 PID: 221 Comm: systemd-udevd Not tainted 5.4.21-rc1-00037-g6f8f5c79416e #1 [ 5.491844] Hardware name: Qualcomm Technologies, Inc. APQ 8016 SBC (DT) [ 5.491849] pstate: 00000005 (nzcv daif -PAN -UAO) [ 5.491858] pc : qcom_iommu_domain_free+0x5c/0x70 [ 5.491865] lr : iommu_group_release+0x44/0x60 [ 5.491867] sp : ffff800011e83600 Starting Network Manager...[ 5.491870] x29: ffff800011e83600 x28: 0000000000000100 [ 5.491893] x19: ffff000036a9e500 x18: 0000000000000001 [ 5.491898] x17: 0000000000000000 x16: 0000000000000000 [ 5.491902] x15: 0000000000000004 x14: 0000000000000000 [ 5.491907] x13: 0000000000000000 x12: ffff00003a137aa0 [ 5.491911] x11: ffff00003a137908 x10: 0000000000000000 [ 5.491916] x9 : ffff00000eb2c098 x8 : ffff00000eb2c090 [ 5.491920] x7 : 00000000400c0000 x6 : 0000000000000004 [ 5.491924] x5 : 0000000000000001 x4 : 0000000000000000 [ 5.491929] x3 : 0000000000000000 x2 : 0000000000000000 [ 5.491933] x1 : ffff00003bdb9680 x0 : ffff000036aa0ab0 [ 5.491938] Call trace: [ 5.491946] qcom_iommu_domain_free+0x5c/0x70 [ 5.491951] iommu_group_release+0x44/0x60 [ 5.491957] kobject_put+0x6c/0xf0 [ 5.491962] kobject_del+0x50/0x68 [ 5.491966] kobject_put+0xd0/0xf0 [ 5.491972] iommu_group_remove_device+0xd8/0xec [ 5.491977] qcom_iommu_remove_device+0x44/0x60 [ 5.491982] iommu_release_device+0x28/0x40 [ 5.491987] iommu_bus_notifier+0xac/0xc0 [ 5.491993] notifier_call_chain+0x58/0x98 [ 5.491998] blocking_notifier_call_chain+0x54/0x78 [ 5.492003] device_del+0x224/0x348 [ 5.492008] platform_device_del.part.0+0x18/0x88 [ 5.492012] platform_device_unregister+0x20/0x38 [ 5.492019] of_platform_device_destroy+0xdc/0xf0 [ 5.492023] device_for_each_child+0x58/0xa0 [ 5.492028] of_platform_depopulate+0x38/0x78 [ 5.492155] msm_pdev_probe+0x1c0/0x308 [msm] [ 5.492166] platform_drv_probe+0x50/0xa0 [ 5.682404] really_probe+0xd4/0x308 [ 5.686388] driver_probe_device+0x54/0xe8 [ 5.690035] device_driver_attach+0x6c/0x78 [ 5.693940] __driver_attach+0x54/0xd0 [ 5.698020] bus_for_each_dev+0x6c/0xc0 [ 5.701838] driver_attach+0x20/0x28 [ 5.705572] bus_add_driver+0x140/0x1e8 [ 5.709390] driver_register+0x60/0x110 [ 5.712950] __platform_driver_register+0x44/0x50 [ 5.716886] msm_drm_register+0x54/0x68 [msm] [ 5.721633] do_one_initcall+0x50/0x190 [ 5.725972] do_init_module+0x50/0x208 [ 5.729615] load_module+0x1d1c/0x2298 [ 5.733435] __do_sys_finit_module+0xd0/0xe8 [ 5.737169] __arm64_sys_finit_module+0x1c/0x28 [ 5.741598] el0_svc_common.constprop.0+0x68/0x160 [ 5.745851] el0_svc_handler+0x20/0x80 [ 5.750709] el0_svc+0x8/0xc [ 5.754443] ---[ end trace 0ebe200932dd18fc ]--- Full test log link, https://lkft.validation.linaro.org/scheduler/job/1226062#L3841 https://lkft.validation.linaro.org/scheduler/job/1227242#L3877 Ref: https://bugs.linaro.org/show_bug.cgi?id=5460 -- Linaro LKFT https://lkft.linaro.org