Description:
After a system upgrade a couple of weeks ago, switching screen resolution from 4K to 1920x1080 results in a blank screen. The only hint that I have right now is a kernel error message:

[ 118.756505] [drm:intel_set_cpu_fifo_underrun_reporting [i915]] *ERROR* uncleared fifo underrun on pipe A
[ 118.756530] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun

Alternatively with both intel and amdgpu drivers enabled:

[ 66.627374] [drm:intel_set_cpu_fifo_underrun_reporting [i915]] *ERROR* uncleared fifo underrun on pipe A
[ 66.627417] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun
[ 67.096108] [drm] PCIE gen 3 link speeds already enabled
[ 67.097678] amdgpu 0000:01:00.0: PCIE GART of 1024M enabled (table at 0x000000F400000000).
[ 76.001042] audit: type=1131 audit(1558651200.156:57): pid=1 uid=0 auid=4294967295 ses=4294967295 msg='unit=geoclue comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=? terminal=? res=success'
[ 81.482198] [drm] PCIE gen 3 link speeds already enabled
[ 81.483849] amdgpu 0000:01:00.0: PCIE GART of 1024M enabled (table at 0x000000F400000000).

I use Full HD resolution instead of 4K whenever I use two monitors (notebook eDP and external HDMI).

I can try downgrading the kernel or gnome shell for testing if necessary.

Additional info:
* package version(s)
linux 5.1.4-arch1-1 (same problem in 5.1.2-arch1-1)
extra/mesa 19.0.4-1 [instalado]
extra/intel-ucode 20190514.a-1 [instalado]
extra/gnome-shell 1:3.32.2-1 (gnome) [instalado]


* config and/or log files etc.
00:00.0 Host bridge: Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor DRAM Controller (rev 06)
00:01.0 PCI bridge: Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor PCI Express x16 Controller (rev 06)
00:02.0 VGA compatible controller: Intel Corporation 4th Gen Core Processor Integrated Graphics Controller (rev 06)
00:03.0 Audio device: Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor HD Audio Controller (rev 06)
00:14.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset Family USB xHCI (rev 04)
00:16.0 Communication controller: Intel Corporation 8 Series/C220 Series Chipset Family MEI Controller #1 (rev 04)
00:1a.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset Family USB EHCI #2 (rev 04)
00:1b.0 Audio device: Intel Corporation 8 Series/C220 Series Chipset High Definition Audio Controller (rev 04)
00:1c.0 PCI bridge: Intel Corporation 8 Series/C220 Series Chipset Family PCI Express Root Port #1 (rev d4)
00:1c.2 PCI bridge: Intel Corporation 8 Series/C220 Series Chipset Family PCI Express Root Port #3 (rev d4)
00:1c.3 PCI bridge: Intel Corporation 8 Series/C220 Series Chipset Family PCI Express Root Port #4 (rev d4)
00:1c.5 PCI bridge: Intel Corporation 8 Series/C220 Series Chipset Family PCI Express Root Port #6 (rev d4)
00:1d.0 USB controller: Intel Corporation 8 Series/C220 Series Chipset Family USB EHCI #1 (rev 04)
00:1f.0 ISA bridge: Intel Corporation HM86 Express LPC Controller (rev 04)
00:1f.2 SATA controller: Intel Corporation 8 Series/C220 Series Chipset Family 6-port SATA Controller 1 [AHCI mode] (rev 04)
00:1f.3 SMBus: Intel Corporation 8 Series/C220 Series Chipset Family SMBus Controller (rev 04)
01:00.0 Display controller: Advanced Micro Devices, Inc. [AMD/ATI] Venus PRO [Radeon HD 8850M / R9 M265X]
03:00.0 Network controller: Intel Corporation Wireless 3160 (rev 83)
04:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 0c)
05:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS5249 PCI Express Card Reader (rev 01)



* link to upstream bug report, if any

Steps to reproduce:
Open gnome control panel, change notebook screen to 1920x1080, results in blank screen.