amdgpu with mst WARNING on blanking

note that i marked disco as 'fix released' but technically it's 'fix committed' - however it's being tracked for disco over in bug 1812427 as part of the normal disco stable update, so for the purposes of this bug, i think it can be considered fix released.

for bionic, this looks like it requires (at least) commit 41b497421a1f07ab99814da740984f907747120b also, which is a bit more complex to backport.

Note - this is the not the only way that this WARNING msg may be printed, this bug is *specifically* in reference to blanking/unblanking the screen reaching this warning/failure.

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-cosmic' to 'verification-done-cosmic'. If the problem still exists, change the tag 'verification-needed-cosmic' to 'verification-failed-cosmic'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-bionic' to 'verification-done-bionic'. If the problem still exists, change the tag 'verification-needed-bionic' to 'verification-failed-bionic'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

booted both 4.15.0-47.50 and 4.18.0-17.18 kernels; blanked screen for both kernels, and after unblanking checked dmesg; the kernel warnings were not shown.

This bug was fixed in the package linux - 4.15.0-47.50

---------------
linux (4.15.0-47.50) bionic; urgency=medium

  * linux: 4.15.0-47.50 -proposed tracker (LP: #1819716)

  * Packaging resync (LP: #1786013)
    - [Packaging] resync getabis
    - [Packaging] update helper scripts
    - [Packaging] resync retpoline extraction

  * C++ demangling support missing from perf (LP: #1396654)
    - [Packaging] fix a mistype

  * arm-smmu-v3 arm-smmu-v3.3.auto: CMD_SYNC timeout (LP: #1818162)
    - iommu/arm-smmu-v3: Fix unexpected CMD_SYNC timeout

  * Crash in nvme_irq_check() when using threaded interrupts (LP: #1818747)
    - nvme-pci: fix out of bounds access in nvme_cqe_pending

  * CVE-2019-9213
    - mm: enforce min addr even if capable() in expand_downwards()

  * CVE-2019-3460
    - Bluetooth: Check L2CAP option sizes returned from l2cap_get_conf_opt

  * amdgpu with mst WARNING on blanking (LP: #1814308)
    - drm/amd/display: Don't use dc_link in link_encoder
    - drm/amd/display: Move wait for hpd ready out from edp power control.
    - drm/amd/display: eDP sequence BL off first then DP blank.
    - drm/amd/display: Fix unused variable compilation error
    - drm/amd/display: Fix warning about misaligned code
    - drm/amd/display: Fix MST dp_blank REG_WAIT timeout

  * tun/tap: unable to manage carrier state from userland (LP: #1806392)
    - tun: implement carrier change

  * CVE-2019-8980
    - exec: Fix mem leak in kernel_read_file

  * raw_skew in timer from the ubuntu_kernel_selftests failed on Bionic
    (LP: #1811194)
    - selftest: timers: Tweak raw_skew to SKIP when ADJ_OFFSET/other clock
      adjustments are in progress

  * [Packaging] Allow overlay of config annotations (LP: #1752072)
    - [Packaging] config-check: Add an include directive

  * CVE-2019-7308
    - bpf: move {prev_,}insn_idx into verifier env
    - bpf: move tmp variable into ax register in interpreter
    - bpf: enable access to ax register also from verifier rewrite
    - bpf: restrict map value pointer arithmetic for unprivileged
    - bpf: restrict stack pointer arithmetic for unprivileged
    - bpf: restrict unknown scalars of mixed signed bounds for unprivileged
    - bpf: fix check_map_access smin_value test when pointer contains offset
    - bpf: prevent out of bounds speculation on pointer arithmetic
    - bpf: fix sanitation of alu op with pointer / scalar type from different
      paths
    - bpf: add various test cases to selftests

  * CVE-2017-5753
    - bpf: properly enforce index mask to prevent out-of-bounds speculation
    - bpf: fix inner map masking to prevent oob under speculation

  * BPF: kernel pointer leak to unprivileged userspace (LP: #1815259)
    - bpf/verifier: disallow pointer subtraction

  * squashfs hardening (LP: #1816756)
    - squashfs: more metadata hardening
    - squashfs metadata 2: electric boogaloo
    - squashfs: more metadata hardening
    - Squashfs: Compute expected length from inode size rather than block length

  * efi/arm/arm64: Allow SetVirtualAddressMap() to be omitted (LP: #1814982)
    - efi/arm/arm64: Allow SetVirtualAddressMap() to be omitted

  * Update ENA driver to version 2.0.3K (LP: #1816806)...

This bug was fixed in the package linux - 4.18.0-17.18

---------------
linux (4.18.0-17.18) cosmic; urgency=medium

  * linux: 4.18.0-17.18 -proposed tracker (LP: #1819624)

  * Packaging resync (LP: #1786013)
    - [Packaging] resync getabis
    - [Packaging] update helper scripts

  * C++ demangling support missing from perf (LP: #1396654)
    - [Packaging] fix a mistype

  * arm-smmu-v3 arm-smmu-v3.3.auto: CMD_SYNC timeout (LP: #1818162)
    - iommu/arm-smmu-v3: Fix unexpected CMD_SYNC timeout

  * Crash in nvme_irq_check() when using threaded interrupts (LP: #1818747)
    - nvme-pci: fix out of bounds access in nvme_cqe_pending

  * CVE-2019-9003
    - ipmi: fix use-after-free of user->release_barrier.rda

  * CVE-2019-9162
    - netfilter: nf_nat_snmp_basic: add missing length checks in ASN.1 cbs

  * CVE-2019-9213
    - mm: enforce min addr even if capable() in expand_downwards()

  * CVE-2019-3460
    - Bluetooth: Check L2CAP option sizes returned from l2cap_get_conf_opt

  * tun/tap: unable to manage carrier state from userland (LP: #1806392)
    - tun: implement carrier change

  * CVE-2019-8980
    - exec: Fix mem leak in kernel_read_file

  * [Packaging] Allow overlay of config annotations (LP: #1752072)
    - [Packaging] config-check: Add an include directive

  * amdgpu with mst WARNING on blanking (LP: #1814308)
    - drm/amd/display: Fix MST dp_blank REG_WAIT timeout

  * CVE-2019-7308
    - bpf: move {prev_,}insn_idx into verifier env
    - bpf: move tmp variable into ax register in interpreter
    - bpf: enable access to ax register also from verifier rewrite
    - bpf: restrict map value pointer arithmetic for unprivileged
    - bpf: restrict stack pointer arithmetic for unprivileged
    - bpf: restrict unknown scalars of mixed signed bounds for unprivileged
    - bpf: fix check_map_access smin_value test when pointer contains offset
    - bpf: prevent out of bounds speculation on pointer arithmetic
    - bpf: fix sanitation of alu op with pointer / scalar type from different
      paths
    - bpf: add various test cases to test_verifier
    - bpf: add various test cases to selftests

  * CVE-2017-5753
    - bpf: fix inner map masking to prevent oob under speculation

  * Use memblock quirk instead of delayed allocation for GICv3 LPI tables
    (LP: #1816425)
    - efi/arm: Revert "Defer persistent reservations until after paging_init()"
    - arm64, mm, efi: Account for GICv3 LPI tables in static memblock reserve
      table

  * efi/arm/arm64: Allow SetVirtualAddressMap() to be omitted (LP: #1814982)
    - efi/arm/arm64: Allow SetVirtualAddressMap() to be omitted

  * Update ENA driver to version 2.0.3K (LP: #1816806)
    - net: ena: update driver version from 2.0.2 to 2.0.3
    - net: ena: fix race between link up and device initalization
    - net: ena: fix crash during failed resume from hibernation

  * Silent "Unknown key" message when pressing keyboard backlight hotkey
    (LP: #1817063)
    - platform/x86: dell-wmi: Ignore new keyboard backlight change event

  * CVE-2018-19824
    - ALSA: usb-audio: Fix UAF decrement if card has no live interfaces in card.c

  * CVE-2019-3459
    - Bluetooth: Verify that l2cap_get...