graphics/drm-fbsd13-kmod: panic during GPU post

[Dan Kotowski]

When kloading amdgpu, the system panics and the following errors are echoed to the console:

[drm ERROR :atom_op_jump] atombios stuck in loop for more than 10secs aborting
[drm ERROR :amdgpu_atom_execute_table_locked] atombios stuck executing AD44 (len 428, WS 20, PS 0) @ 0xAE76
[drm ERROR :amdgpu_atom_execute_table_locked] atombios stuck executing A984 (len 158, WS 0, PS 8) @ 0xA9E7

Perhaps there's a tunable I'm missing? Somebody elsewhere suggested setting pcie_gen_cap=0x4 but I'm not seeing how to do that at load-time in FreeBSD.

Running:
13.0-STABLE #4 stable/13-n244517-8874f305d81
drm-fbsd13-kmod-5.4.92.g20210202

Dump header from device: /dev/nda0p2
  Architecture: aarch64
  Architecture Version: 1
  Dump Length: 1275293696
  Blocksize: 512
  Compression: none
  Dumptime: 2021-02-17 22:50:21 +0000
  Hostname: honeycomb.a9development.com
  Magic: FreeBSD Kernel Dump
  Version String: FreeBSD 13.0-STABLE #4 stable/13-n244517-8874f305d81: Sun Feb 14 03:03:23 UTC 2021
    root at honeycomb.a9development.com:/usr/obj/usr/src/arm64.aarch64/sys/HONEYCOMB-MMCCAM
  Panic String: Unhandled System Error
  Dump Parity: 3604485663
  Bounds: 4
  Dump Status: good

root at honeycomb:~ # kldload -v amdgpu
<6>[drm] amdgpu kernel modesetting enabled.
drmn0: <drmn> on vgapci0
vgapci0: child drmn0 requested pci_enable_io
vgapci0: child drmn0 requested pci_enable_io
sysctl_warn_reuse: can't re-use a leaf (hw.dri.debug)!
<6>[drm] initializing kernel modesetting (POLARIS12 0x1002:0x699F 0x1DA2:0xE367 0xC7).
<6>[drm] register mmio base: 0x40000000
<6>[drm] register mmio size: 262144
<6>[drm] add ip block number 0 <vi_common>
<6>[drm] add ip block number 1 <gmc_v8_0>
<6>[drm] add ip block number 2 <tonga_ih>
<6>[drm] add ip block number 3 <gfx_v8_0>
<6>[drm] add ip block number 4 <sdma_v3_0>
<6>[drm] add ip block number 5 <powerplay>
<6>[drm] add ip block number 6 <dm>
<6>[drm] add ip block number 7 <uvd_v6_0>
<6>[drm] add ip block number 8 <vce_v3_0>
<6>[drm] UVD is enabled in VM mode
<6>[drm] UVD ENC is enabled in VM mode
<6>[drm] VCE enabled in VM mode
<6>[drm] GPU posting now...
[drm ERROR :atom_op_jump] atombios stuck in loop for more than 10secs aborting
[drm ERROR :amdgpu_atom_execute_table_locked] atombios stuck executing AD44 (len 428, WS 20, PS 0) @ 0xAE76
[drm ERROR :amdgpu_atom_execute_table_locked] atombios stuck executing A984 (len 158, WS 0, PS 8) @ 0xA9E7
drmn0: gpu post error!
drmn0: Fatal error during GPU init
<6>[drm] amdgpu: finishing device.
Warning: can't remove non-dynamic nodes (dri)!
device_attach: drmn0 attach returned 22
  x0:                b
  x1:                0
  x2:     ffffffffee00
  x3:               33
  x4:         40100401
  x5:    800208000aaaa
  x6:                1
  x7:            f5ff5
  x8:              130
  x9:                0
 x10:                0
 x11:         80130000
 x12:              427
 x13:                0
 x14:         80000000
 x15:         402bd5e1
 x16:         403cd89c
 x17:     ffffffffe540
 x18:                0
 x19:     ffffffffeb30
 x20:                0
 x21:           200bd5
 x22:                1
 x23:     ffffffffee13
 x24:                0
 x25:                1
 x26:           200b2a
 x27:           200c82
 x28:                1
 x29:     ffffffffea80
  sp:     ffffffffe550
  lr:           2110fc
 elr:         403cd8a4
spsr:         80000200
 far:                0
 esr:         bf000000
panic: Unhandled System Error
cpuid = 7
time = 1613602221
KDB: stack backtrace:
#0 0xffff000000443e6c at kdb_backtrace+0x60
#1 0xffff0000003ee0cc at vpanic+0x184
#2 0xffff0000003edf44 at panic+0x44
#3 0xffff0000007048ac at do_serror+0x40
#4 0xffff0000006e5c9c at handle_serror+0x88
Uptime: 10m52s