I run an AMD A8-9600 R7 IGP (Carizzo) using amdgpu. System has been running
smoothly for a long time.
After a kernel upgrade:
- When booting, most of the time, after I see the first few lines of boot
screen logging, the display briefly flashes and then turns off, with the
monitor going to standby. Then the monitor comes back on, but stays black.
Also, switching to other terminals (Ctrl-Alt-F1) does nothing.
- About one out of 10 times, the system comes up to KDE properly, but no
accelerated graphics like desktop effects, HW video decoding etc.
- I can reliably boot in recovery and then startx, but that obviously does not
have accelerated graphics, either.
- Behavior is the same no matter which version kernel I boot - in particular
also the kernel that had been working fine before has the above issues now. 

When I run mkinitrd, I get
[code]
dracut: Possible missing firmware "amdgpu/stoney_ce.bin" for kernel module
"amdgpu.ko"
dracut: Possible missing firmware "amdgpu/carrizo_rlc.bin" for kernel module
"amdgpu.ko"
dracut: Possible missing firmware "amdgpu/carrizo_mec2.bin" for kernel module
"amdgpu.ko"
dracut: Possible missing firmware "amdgpu/carrizo_mec.bin" for kernel module
"amdgpu.ko"
dracut: Possible missing firmware "amdgpu/carrizo_me.bin" for kernel module
"amdgpu.ko"
dracut: Possible missing firmware "amdgpu/carrizo_pfp.bin" for kernel module
"amdgpu.ko"
dracut: Possible missing firmware "amdgpu/carrizo_ce.bin" for kernel module
"amdgpu.ko"
dracut: Possible missing firmware "amdgpu/topaz_sdma1.bin" for kernel module
"amdgpu.ko"
[/code]

But these files are clearly present:
[code]
# ll /lib/firmware/amdgpu
total 9636
-rw-r--r-- 1 root root   8832 Mai 30  2017 carrizo_ce.bin
-rw-r--r-- 1 root root  17024 Mai 30  2017 carrizo_me.bin
-rw-r--r-- 2 root root 262784 Mai 30  2017 carrizo_mec2.bin
-rw-r--r-- 2 root root 262784 Mai 30  2017 carrizo_mec.bin
-rw-r--r-- 1 root root  17024 Mai 30  2017 carrizo_pfp.bin
-rw-r--r-- 1 root root  18932 Mai 30  2017 carrizo_rlc.bin
-rw-r--r-- 2 root root  10624 Mai 30  2017 carrizo_sdma1.bin
-rw-r--r-- 2 root root  10624 Mai 30  2017 carrizo_sdma.bin
-rw-r--r-- 1 root root 268000 Mai 30  2017 carrizo_uvd.bin
-rw-r--r-- 1 root root 175840 Mai 30  2017 carrizo_vce.bin
-rw-r--r-- 2 root root   8832 Mai 30  2017 fiji_ce.bin
[/code]

More info:

[code]
# cat /proc/cmdline                                                             
BOOT_IMAGE=/boot/vmlinuz-4.4.104-39-default
root=UUID=68f92734-8c00-4cb5-9800-ca7e17df9309
resume=/dev/disk/by-id/ata-Samsung_SSD_840_Series_S19HNEBD343680A-part2
splash=nosplash quiet showopts
[/code]

So no "vga=" or anything.

[code]
# lsmod | grep -i amd
edac_mce_amd           28672  0 
amdkfd                139264  1 
amd_iommu_v2           20480  1 amdkfd
amdgpu                679936  0 
i2c_algo_bit           16384  1 amdgpu
drm_kms_helper        155648  1 amdgpu
ttm                   106496  1 amdgpu
drm                   393216  3 ttm,drm_kms_helper,amdgpu
[/code]

[code]
# lspci -nnk | grep -A3 VGA
00:01.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc.
[AMD/ATI] Carrizo [1002:9874] (rev e2)
        Subsystem: Advanced Micro Devices, Inc. [AMD/ATI] Device [1002:1e20]
        Kernel modules: amdgpu
00:01.1 Audio device [0403]: Advanced Micro Devices, Inc. [AMD/ATI] Kabini
HDMI/DP Audio [1002:9840]
[/code]

So it seems the amdgpu driver is loaded and used.

[code]
# glxgears
[/code]

shows gears but runs a bit choppy.

I also described this here:
https://forums.opensuse.org/showthread.php/529291-AMDGPU-broken-after-Kernel-Upgrade?p=2852630#post2852630

And it has been pointed out that this might be related to
https://bugzilla.opensuse.org/show_bug.cgi?id=1072431