drm-fbsd12.0-kmod keeps panic with AMD card

[abi]

Hello,

I have panics with graphics/drm-fbsd12.0-kmod with ATI card. I've opened 
PR several month ago, the suggestion was to switch to amdgpu (how that's 
possible with Caicos card). The old version of DRM (drm-fbsd11.2-kmod) 
doesn't have the issue, but I fear once 11  EOL, I'll get problems.

Maybe you can suggest something? Crashes look similar to each other.

Fatal trap 12: page fault while in kernel mode
cpuid = 11; apic id = 0b
fault virtual address    = 0x4000032e6
fault code        = supervisor read data, page not present
instruction pointer    = 0x20:0xffffffff82cc12b4
stack pointer            = 0x28:0xfffffe0090b10070
frame pointer            = 0x28:0xfffffe0090b100a0
code segment        = base 0x0, limit 0xfffff, type 0x1b
             = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags    = interrupt enabled, resume, IOPL = 0
current process        = 1237 (Xorg:rcs0)
trap number        = 12
panic: page fault
cpuid = 11
time = 1559974206
KDB: stack backtrace:
#0 0xffffffff80be7977 at kdb_backtrace+0x67
#1 0xffffffff80b9b563 at vpanic+0x1a3
#2 0xffffffff80b9b3b3 at panic+0x43
#3 0xffffffff8107496f at trap_fatal+0x35f
#4 0xffffffff810749c9 at trap_pfault+0x49
#5 0xffffffff81073fee at trap+0x29e
#6 0xffffffff8104f315 at calltrap+0x8
#7 0xffffffff82cd8f51 at radeon_sa_bo_new+0x361
#8 0xffffffff82cc85b1 at radeon_ib_get+0x31
#9 0xffffffff82cb3ecf at radeon_cs_ioctl+0x25f
#10 0xffffffff82dafca6 at drm_ioctl_kernel+0xf6
#11 0xffffffff82daff41 at drm_ioctl+0x281
#12 0xffffffff82df1bd4 at linux_file_ioctl+0x204
#13 0xffffffff80c04f3d at kern_ioctl+0x26d
#14 0xffffffff80c04c5e at sys_ioctl+0x15e
#15 0xffffffff81075449 at amd64_syscall+0x369
#16 0xffffffff8104fbfd at fast_syscall_common+0x101

Uptime: 2m25s


Dmesg bits for card:

[drm] initializing kernel modesetting (CAICOS 0x1002:0x677B 
0x1043:0x3025 0x00).
[drm:radeon_device_init] Unable to find PCI I/O BAR
[drm:radeon_atombios_init] Unable to find PCI I/O BAR; using MMIO for 
ATOM IIO
ATOM BIOS: 677BHB.13.12.0.49.AS03
drmn0: VRAM: 1024M 0x0000000000000000 - 0x000000003FFFFFFF (1024M used)
drmn0: GTT: 1024M 0x0000000040000000 - 0x000000007FFFFFFF
Failed to add WC MTRR for [0xe0000000-0xefffffff]: -22; performance may 
suffer
[drm] Detected VRAM RAM=1024M, BAR=256M
[drm] RAM width 64bits DDR
[TTM] Zone  kernel: Available graphics memory: 8300262 kiB
[TTM] Zone   dma32: Available graphics memory: 2097152 kiB
[TTM] Initializing pool allocator
[drm] radeon: 1024M of VRAM memory ready
[drm] radeon: 1024M of GTT memory ready.
[drm] Loading CAICOS Microcode
drmn0: successfully loaded firmware image with name: radeon/CAICOS_pfp.bin
drmn0: successfully loaded firmware image with name: radeon/CAICOS_me.bin
drmn0: successfully loaded firmware image with name: radeon/BTC_rlc.bin
drmn0: successfully loaded firmware image with name: radeon/CAICOS_mc.bin
drmn0: successfully loaded firmware image with name: radeon/CAICOS_smc.bin
[drm] Internal thermal controller without fan control
[drm] radeon: dpm initialized
drmn0: successfully loaded firmware image with name: radeon/SUMO_uvd.bin