I had the same problem with Ryzen 2400G on kernels 5.2, 5.3 and 5.4, but it
would only be reproduced when X was running. If I stop X before going to sleep,
wakeup would work. I managed to fix it by reverting the following commit in X
driver:
https://github.com/freedesktop/xorg-xf86-video-amdgpu/commit/a2b32e72fdaff3007a79b84929997d8176c2d512