fence_wait returned with error -512

[Steve Kargl]

Because drm2 in the base system is going away, I install
drm-stable-kmod.  In doing so, I also removed the old drm2
modules under /boot/kernel to ensure that I picked up the
modules from /boot/modules.  To /etc/rc.conf, I added the
line 'kld_list=/bootmodules/radeonkms.ko'.  Upon reboot,
I see

troutmask:kargl[203] kldstat
Id Refs Address                Size Name
 1   68 0xffffffff80200000  10033d8 kernel
 2    1 0xffffffff813af000    1e1c8 geom_eli.ko
 3    2 0xffffffff813ce000    4ec40 crypto.ko
 4    2 0xffffffff8141d000     f718 zlib.ko
 5    1 0xffffffff8142d000    531e8 linux.ko
 6    3 0xffffffff81481000     8ed8 linux_common.ko
 7    1 0xffffffff8148a000     f800 tmpfs.ko
 8    1 0xffffffff81619000     471c linprocfs.ko
 9    1 0xffffffff8161e000   158658 radeonkms.ko
10    1 0xffffffff81777000    70fb0 drm.ko
11    2 0xffffffff817e8000     b008 agp.ko
12    3 0xffffffff817f4000     d220 linuxkpi_gplv2.ko
13    2 0xffffffff81802000      6c0 debugfs.ko
14    1 0xffffffff81803000     12f7 radeon_CAICOS_pfp_bin.ko
15    1 0xffffffff81805000     16f5 radeon_CAICOS_me_bin.ko
16    1 0xffffffff81807000      d71 radeon_BTC_rlc_bin.ko
17    1 0xffffffff81808000     5f95 radeon_CAICOS_mc_bin.ko
18    1 0xffffffff8180e000     6137 radeon_CAICOS_smc_bin.ko
19    1 0xffffffff81815000    32293 radeon_SUMO_uvd_bin.ko
20    1 0xffffffff81848000      df0 cpuctl.ko
21    1 0xffffffff81849000     23f8 intpm.ko
 
and 'dmesg | grep drm' reveals

[drm] Initialized
[drm] radeon kernel modesetting enabled.
drmn0: <drmn> on vgapci0
vgapci0: child drmn0 requested pci_enable_io
vgapci0: child drmn0 requested pci_enable_io
[drm] initializing kernel modesetting (CAICOS 0x1002:0x6779 0x1092:0x6450 0x00).
[drm] register mmio base: 0xFEA20000
[drm] register mmio size: 131072
[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
drmn0: VRAM: 1024M 0x0000000000000000 - 0x000000003FFFFFFF (1024M used)
drmn0: GTT: 1024M 0x0000000040000000 - 0x000000007FFFFFFF
[drm] Detected VRAM RAM=1024M, BAR=256M
[drm] RAM width 64bits DDR
[drm] radeon: 1024M of VRAM memory ready
[drm] radeon: 1024M of GTT memory ready.
[drm] Loading CAICOS Microcode
[drm] Internal thermal controller with fan control
[drm] radeon: dpm initialized
[drm] GART: num cpu pages 262144, num gpu pages 262144
[drm] enabling PCIE gen 2 link speeds, disable with radeon.pcie_gen2=0
[drm] PCIE GART of 1024M enabled (table at 0x0000000000162000).
drmn0: WB enabled
drmn0: fence driver on ring 0 use gpu addr 0x0000000040000c00 and cpu addr 0x0xfffff8000789fc00
drmn0: fence driver on ring 3 use gpu addr 0x0000000040000c0c and cpu addr 0x0xfffff8000789fc0c
drmn0: fence driver on ring 5 use gpu addr 0x0000000000072118 and cpu addr 0x0xfffff800c0072118
[drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[drm] Driver supports precise vblank timestamp query.
drmn0: radeon: MSI limited to 32-bit
[drm] radeon: irq initialized.
[drm] ring test on 0 succeeded in 4 usecs
[drm] ring test on 3 succeeded in 6 usecs
[drm] ring test on 5 succeeded in 3 usecs
[drm] UVD initialized successfully.
[drm] ib test on ring 0 succeeded in 0 usecs
[drm] ib test on ring 3 succeeded in 0 usecs
[drm] ib test on ring 5 succeeded
[drm] hw_i2c forced on, you may experience display detection problems!
[drm] Connector HDMI-A-1: get mode from tunables:
[drm]   - kern.vt.fb.modes.HDMI-A-1
[drm]   - kern.vt.fb.default_mode
[drm] Connector DVI-I-1: get mode from tunables:
[drm]   - kern.vt.fb.modes.DVI-I-1
[drm]   - kern.vt.fb.default_mode
[drm] Connector VGA-1: get mode from tunables:
[drm]   - kern.vt.fb.modes.VGA-1
[drm]   - kern.vt.fb.default_mode
[drm] Radeon Display Connectors
[drm] Connector 0:
[drm]   HDMI-A-1
[drm]   HPD2
[drm]   DDC: 0x6460 0x6460 0x6464 0x6464 0x6468 0x6468 0x646c 0x646c
[drm]   Encoders:
[drm]     DFP1: INTERNAL_UNIPHY1
[drm] Connector 1:
[drm]   DVI-I-1
[drm]   HPD4
[drm]   DDC: 0x6450 0x6450 0x6454 0x6454 0x6458 0x6458 0x645c 0x645c
[drm]   Encoders:
[drm]     DFP2: INTERNAL_UNIPHY
[drm] Connector 2:
[drm]   VGA-1
[drm]   DDC: 0x6430 0x6430 0x6434 0x6434 0x6438 0x6438 0x643c 0x643c
[drm]   Encoders:
[drm]     CRT1: INTERNAL_KLDSCP_DAC1
[drm] fb mappable at 0xC0363000
[drm] vram apper at 0xC0000000
[drm] size 8294400
[drm] fb depth is 24
[drm]    pitch is 7680
name=drmn0 flags=0x0 stride=7680 bpp=32
drmn0: fb0: radeondrmfb frame buffer device
[drm] Initialized radeon 2.48.0 20080528 for drmn on minor 0

My console and /var/log/messages now contains a slew of 

fence_wait returned with error -512

This message is coming from /boot/modules/drm.ko

% strings /boot/modules/drm.ko  | grep fence_wait
fence_wait returned with error %d

Why?

-- 
Steve