...
Apr 14 23:08:33 x505z kernel: [drm] amdgpu kernel modesetting enabled.
Apr 14 23:08:33 x505z kernel: drmn0: <drmn> on vgapci0
Apr 14 23:08:33 x505z kernel: vgapci0: child drmn0 requested pci_enable_io
Apr 14 23:08:33 x505z syslogd: last message repeated 1 times
Apr 14 23:08:33 x505z kernel: [drm] initializing kernel modesetting (RAVEN 0x1002:0x15DD 0x1043:0x1091 0xC4).
Apr 14 23:08:33 x505z kernel: [drm] register mmio base: 0xFE700000
Apr 14 23:08:33 x505z kernel: [drm] register mmio size: 524288
Apr 14 23:08:33 x505z kernel: [drm] PCI I/O BAR is not found.
Apr 14 23:08:33 x505z kernel: ugen1.4: <vendor 0x8087 product 0x0a2b> at usbus1
Apr 14 23:08:33 x505z kernel: drmn0: successfully loaded firmware image with name: amdgpu/raven_gpu_info.bin
Apr 14 23:08:33 x505z kernel: [drm] probing gen 2 caps for device 1022:15db = 700d03/e
Apr 14 23:08:33 x505z kernel: [drm] probing mlw for device 1002:15dd = 400d03
Apr 14 23:08:33 x505z kernel: [drm] VCN decode is enabled in VM mode
Apr 14 23:08:33 x505z kernel: [drm] VCN encode is enabled in VM mode
Apr 14 23:08:33 x505z kernel: ATOM BIOS: 113-RAVEN-105
Apr 14 23:08:33 x505z kernel: [drm] vm size is 262144 GB, 4 levels, block size is 9-bit, fragment size is 9-bit
Apr 14 23:08:33 x505z kernel: drmn0: VRAM: 1024M 0x000000F400000000 - 0x000000F43FFFFFFF (1024M used)
Apr 14 23:08:33 x505z kernel: drmn0: GTT: 1024M 0x000000F500000000 - 0x000000F53FFFFFFF
Apr 14 23:08:33 x505z kernel: Successfully added WC MTRR for [0xe0000000-0xefffffff]: 0; 
Apr 14 23:08:33 x505z kernel: [drm] Detected VRAM RAM=1024M, BAR=256M
Apr 14 23:08:33 x505z kernel: [drm] RAM width 64bits UNKNOWN
Apr 14 23:08:33 x505z kernel: [drm:amdgpu_ttm_global_init] Failed setting up TTM memory accounting subsystem.
Apr 14 23:08:33 x505z kernel: [drm:amdgpu_device_ip_init] sw_init of IP block <gmc_v9_0> failed -12
Apr 14 23:08:33 x505z kernel: drmn0: amdgpu_device_ip_init failed
Apr 14 23:08:33 x505z kernel: drmn0: Fatal error during GPU init
Apr 14 23:08:33 x505z kernel: [drm] amdgpu: finishing device.
Apr 14 23:08:33 x505z kernel: vgapci0: child drmn0 requested pci_disable_io
...

With r345929 - OK, r345932 and later - broken.

#define	ENOMEM		12		/* Cannot allocate memory */
Patch add return -ENOMEM on error:
https://svnweb.freebsd.org/base/stable/12/sys/compat/linuxkpi/common/include/linux/sysfs.h?sortby=file&r1=345932&r2=345931&pathrev=345932