Hybrid (i915+radeon/amdgpu) graphics don't work after resume

When my laptop resumes from suspend, the secondary GPU (Radeon R7 M265) does not work. Prior to suspend I can use it. After suspend, trying DRI_PRIME=1 glxinfo | grep OpenGL simply fails (see attached file).

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: xorg 1:7.7+19ubuntu7
ProcVersionSignature: Ubuntu 4.15.0-15.16-lowlatency 4.15.15
Uname: Linux 4.15.0-15-lowlatency x86_64
ApportVersion: 2.20.9-0ubuntu6
Architecture: amd64
BootLog: Error: [Errno 13] Permission denied: '/var/log/boot.log'
CompositorRunning: None
CurrentDesktop: ubuntu:GNOME
Date: Sat Apr 21 16:14:15 2018
DistUpgraded: Fresh install
DistroCodename: bionic
DistroVariant: ubuntu
ExtraDebuggingInterest: Yes, including running git bisection searches
GraphicsCard:
 Intel Corporation HD Graphics 520 [8086:1916] (rev 07) (prog-if 00 [VGA controller])
   Subsystem: Hewlett-Packard Company Skylake GT2 [HD Graphics 520] [103c:8079]
 Advanced Micro Devices, Inc. [AMD/ATI] Opal XT [Radeon R7 M265] [1002:6604] (rev 81) (prog-if 00 [VGA controller])
   Subsystem: Hewlett-Packard Company Opal XT [Radeon R7 M265] [103c:814f]
InstallationDate: Installed on 2018-04-03 (18 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Alpha amd64 (20180402)
MachineType: HP HP EliteBook 850 G3
ProcKernelCmdLine: BOOT_IMAGE=/bionic/vmlinuz-4.15.0-15-lowlatency.efi.signed root=UUID=b6480aee-7c63-4ce4-9e8d-cdbef768b982 ro rootflags=subvol=@,relatime,autodefrag,space_cache quiet splash module.sig_enforce=1 intel_pstate=skylake_hwp vt.handoff=7
SourcePackage: xorg
Symptom: display
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 07/31/2016
dmi.bios.vendor: HP
dmi.bios.version: N75 Ver. 01.10
dmi.board.name: 8079
dmi.board.vendor: HP
dmi.board.version: KBC Version 85.6F
dmi.chassis.asset.tag: 5CG6351LQL
dmi.chassis.type: 10
dmi.chassis.vendor: HP
dmi.modalias: dmi:bvnHP:bvrN75Ver.01.10:bd07/31/2016:svnHP:pnHPEliteBook850G3:pvr:rvnHP:rn8079:rvrKBCVersion85.6F:cvnHP:ct10:cvr:
dmi.product.family: 103C_5336AN G=N L=BUS B=HP S=ELI
dmi.product.name: HP EliteBook 850 G3
dmi.sys.vendor: HP
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.91-2
version.libgl1-mesa-dri: libgl1-mesa-dri 18.0.0~rc5-1ubuntu1
version.libgl1-mesa-glx: libgl1-mesa-glx 18.0.0~rc5-1ubuntu1
version.xserver-xorg-core: xserver-xorg-core 2:1.19.6-1ubuntu4
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:18.0.1-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20171229-1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.15-2