Resuming from DPMS results in screen flashing on Dell Latitude 7200 2-in-1

Resuming the display after powersave results in flashes of the screen once per second with the display black most of the time. The display seems fine if it doesn't go into powersave. If you have an external display connected, they both blink together while trying to power on. If you close the keyboard on the tablet, the external display resumes properly.

i915 0000:00:02.0: [drm:intel_dp_start_link_train [i915]] Channel equalization failed 5 times
i915 0000:00:02.0: [drm:intel_dp_start_link_train [i915]] [CONNECTOR:95:eDP-1] Link Training failed at link rate = 270000, lane count = 2

This seems similar to, but slightly different from, #170 (closed)

lspci says "VGA compatible controller: Intel Corporation UHD Graphics 620 (Whiskey Lake) (rev 02)"

edid-decode /sys/class/drm/card0-eDP-1/edid
Extracted contents:
header:          00 ff ff ff ff ff ff 00
serial number:   4d 10 a3 14 00 00 00 00 05 1d
version:         01 04
basic params:    a5 1a 11 78 0e
chroma info:     de 50 a3 54 4c 99 26 0f 50 54
established:     00 00 00
standard:        01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01
descriptor 1:    29 40 80 a0 70 00 24 50 30 20 3a 00 03 ad 10 00 00 18
descriptor 2:    54 33 80 a0 70 00 24 50 30 20 3a 00 03 ad 10 00 00 18
descriptor 3:    00 00 00 fe 00 4d 52 4e 39 37 80 4c 51 31 32 33 4e 31
descriptor 4:    00 00 00 00 00 02 41 03 28 01 12 00 00 0a 01 0a 20 20
extensions:      00
checksum:        63

EDID version: 1.4
Manufacturer: SHP Model 14a3 Serial Number 0
Made in week 5 of 2019
Digital display
8 bits per primary color channel
DisplayPort interface
Maximum image size: 26 cm x 17 cm
Gamma: 2.20
Supported color formats: RGB 4:4:4, YCrCb 4:4:4
Default (sRGB) color space is primary color space
First detailed timing includes the native pixel format and preferred refresh rate
Display x,y Chromaticity:
  Red:   0.6396, 0.3291
  Green: 0.2998, 0.5996
  Blue:  0.1494, 0.0595
  White: 0.3125, 0.3281
Established timings supported:
Standard timings supported:
Detailed mode: Clock 164.250 MHz, 259 mm x 173 mm
               1920 1968 2000 2080 hborder 0
               1280 1283 1293 1316 vborder 0
               -hsync -vsync 
               VertFreq: 60 Hz, HorFreq: 78966 Hz
Detailed mode: Clock 131.400 MHz, 259 mm x 173 mm
               1920 1968 2000 2080 hborder 0
               1280 1283 1293 1316 vborder 0
               -hsync -vsync 
               VertFreq: 48 Hz, HorFreq: 63173 Hz
ASCII string: MRN97
Manufacturer-specified data, tag 0
Checksum: 0x63 (valid)
EDID block does NOT conform to EDID 1.4!
	sRGB is signaled, but the chromaticities do not match
	Missing name descriptor
	Missing monitor ranges
	Detailed block string not properly terminated

With the screen on after boot:

cat /sys/kernel/debug/dri/0/i915_edp_psr_status 
Sink support: yes [0x03]
PSR mode: PSR2 enabled
Source PSR ctl: enabled [0xc0000236]
Source PSR status: DEEP_SLEEP [0x80000100]
Busy frontbuffer bits: 0x00000000
Frame:	PSR2 SU blocks:
0	0
1	0
2	0
3	0
4	0
5	0
6	0
7	0

After the screen turns off:

cat /sys/kernel/debug/dri/0/i915_edp_psr_status 
Sink support: yes [0x03]
PSR mode: disabled
PSR sink not reliable: no

Caught while trying to power on? It goes back to the above 'disabled' most of the time.

cat /sys/kernel/debug/dri/0/i915_edp_psr_status 
Sink support: yes [0x03]
PSR mode: PSR2 enabled
Source PSR ctl: enabled [0xc0000236]
Source PSR status: IDLE [0x04000010]
Busy frontbuffer bits: 0x00000000
Frame:	PSR2 SU blocks:
0	0
1	0
2	0
3	0
4	0
5	0
6	0
7	0

dell-7200-dmesg-i915-drm-tip.txt

Please let me know if there is anything I should try out.