[Bug 1814308] Re: amdgpu with mst WARNING on blanking

** Changed in: linux (Ubuntu Cosmic)
Status: In Progress => Fix Committed

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https://bugs.launchpad.net/bugs/1814308

Title:
amdgpu with mst WARNING on blanking

Status in linux package in Ubuntu:
Fix Released
Status in linux source package in Xenial:
Invalid
Status in linux source package in Bionic:
In Progress
Status in linux source package in Cosmic:
Fix Committed
Status in linux source package in Disco:
Fix Released

Bug description:
[impact]

The amdgpu driver, when configured with MST monitors (i.e. displayport
"daisy-chaining"), encounters a WARNING when blanking - such as when
the display(s) are put to sleep after idle timeout.

[test case]

on a system with a amd gpu using the amdgpu driver, that is capable
and configured for displayport mst (with multiple dp daisy chained
monitors), blank the screen and then wake up the screen. This will be
logged:

    [drm:generic_reg_wait [amdgpu]] *ERROR* REG_WAIT timeout 10us * 3000 tries - dce110_stream_encoder_dp_blank line:944
    ------------[ cut here ]------------
    WARNING: CPU: 0 PID: 2201 at /var/lib/dkms/amdgpu/18.50-690240/build/amd/amdgpu/../display/dc/dc_helper.c:249 generic_reg_wait+0xe7/0x160 [amdgpu]
    Call Trace:
     dce110_stream_encoder_dp_blank+0x11c/0x180 [amdgpu]
     core_link_disable_stream+0x40/0x230 [amdgpu]
     ? generic_reg_update_ex+0xdb/0x130 [amdgpu]
     dce110_reset_hw_ctx_wrap+0xb7/0x1f0 [amdgpu]
     dce110_apply_ctx_to_hw+0x30/0x430 [amdgpu]
     ? dce110_apply_ctx_for_surface+0x206/0x260 [amdgpu]
     dc_commit_state+0x2ba/0x4d0 [amdgpu]
     amdgpu_dm_atomic_commit_tail+0x297/0xd70 [amdgpu]
     ? amdgpu_bo_pin_restricted+0x58/0x260 [amdgpu]
     ? wait_for_completion_timeout+0x1f/0x120
     ? wait_for_completion_interruptible+0x1c/0x160
     commit_tail+0x3d/0x60 [drm_kms_helper]
     drm_atomic_helper_commit+0xf6/0x100 [drm_kms_helper]
     drm_atomic_connector_commit_dpms+0xe5/0xf0 [drm]
     drm_mode_obj_set_property_ioctl+0x14f/0x250 [drm]
     drm_mode_connector_property_set_ioctl+0x2e/0x40 [drm]
     drm_ioctl+0x1e0/0x430 [drm]
     ? drm_mode_connector_set_obj_prop+0x70/0x70 [drm]
     ? ep_read_events_proc+0xb0/0xb0
     ? ep_scan_ready_list.constprop.18+0x1e6/0x1f0
     ? timerqueue_add+0x52/0x80
     amdgpu_drm_ioctl+0x49/0x80 [amdgpu]
     do_vfs_ioctl+0x90/0x5f0
     SyS_ioctl+0x74/0x80
     do_syscall_64+0x74/0x140
     entry_SYSCALL_64_after_hwframe+0x3d/0xa2
    ---[ end trace 3ed7b77a97d60f72 ]---

[regression potential]

this modifies the sequence of actions during link disabling, so any
regressions would appear at that time.

[other info]

this is from upstream 8c9d90eebd23b6d40ddf4ce5df5ca2b932336a06

this is included in disco from bug 1812427

this is needed in bionic and cosmic

the xenial kernel does not (reliably) support dp mst, so this is not
needed there

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