No usable event timer found on RPI2

Sat Apr 9 02:02:38 UTC 2016

Hi all,

For the last few days attempts to boot new kernels have ended with a panic,
"No usable event timer found". Thinking I'd damaged the kernel config file,
I replaced it with an unmolested version via svnlite. No improvement. The 
sources were downloaded yesterday. A kernel from a few days earlier seems
to work fine. The only error found during kernel build said something about

--- elf_note.o ---
/usr/src/sys/arm/arm/elf_note.S:35:1: warning: DWARF2 only supports one section per compilation unit
.pushsection .note.tag ; .balign 4 ; .long 2f - 1f ; .long 4f - 3f ; .long 1 ; 1: .asciz "FreeBSD" ; 2: .balign 4 ; 3: 
.long 1100105 ; 4: .balign 4 ; .popsection;
^
ctfconvert -L VERSION -g elf_note.o
ERROR: ctfconvert: rc = -1 No entry found [dwarf_next_cu_header_c(61)]
--- exception.o ---

but this could well be an existing issue that simply hadn't been noticed.

Here's the boot transcript:

U-Boot 2015.04 (May 30 2015 - 22:13:58)

DRAM:  944 MiB
WARNING: Caches not enabled
RPI 2 Model B
MMC:   bcm2835_sdhci: 0
reading uboot.env

** Unable to read "uboot.env" from mmc0:1 **
Using default environment

In:    serial
Out:   lcd
Err:   lcd
Net:   Net Initialization Skipped
No ethernet found.
Hit any key to stop autoboot:  0 
Booting from: mmc 0 ubldr
reading ubldr
265922 bytes read in 207 ms (1.2 MiB/s)
## Starting application at 0x02000094 ...
Consoles: U-Boot console  
Compatible U-Boot API signature found @3ab4a4c8

FreeBSD/armv6 U-Boot loader, Revision 1.2
(bob at fbsd.zefox.com, Thu Jun 11 08:12:11 PDT 2015)

DRAM: 944MB
Number of U-Boot devices: 1
U-Boot env: loaderdev='mmc 0'
Found U-Boot device: disk
  Checking unit=0 slice=<auto> partition=<auto>... good.
/boot/kernel/kernel data=0x60fd24+0x1002dc syms=[0x4+0x83b20+0x4+0x97230]

Hit [Enter] to boot immediately, or any other key for command prompt.
Booting [/boot/kernel/kernel]...               
Using DTB provided by U-Boot at address 0x100.
Kernel entry at 0x2200100...
Kernel args: (null)
KDB: debugger backends: ddb
KDB: current backend: ddb
Copyright (c) 1992-2016 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
	The Regents of the University of California. All rights reserved.
FreeBSD is a registered trademark of The FreeBSD Foundation.
FreeBSD 11.0-CURRENT #70 r297693: Fri Apr  8 16:28:30 PDT 2016
    root at www.zefox.com:/usr/obj/usr/src/sys/RPI2 arm
FreeBSD clang version 3.8.0 (tags/RELEASE_380/final 262564) (based on LLVM 3.8.0)
VT: init without driver.
sema_sysinit
CPU: Cortex A7 rev 5 (Cortex-A core)
 Supported features: ARM_ISA THUMB2 JAZELLE THUMBEE ARMv4 Security_Ext
 WB enabled LABT branch prediction disabled
LoUU:2 LoC:3 LoUIS:2 
Cache level 1: 
 32KB/64B 4-way data cache WB Read-Alloc Write-Alloc
 32KB/32B 2-way instruction cache Read-Alloc
Cache level 2: 
 512KB/64B 8-way unified cache WB Read-Alloc Write-Alloc
real memory  = 989851648 (943 MB)
avail memory = 957444096 (913 MB)
FreeBSD/SMP: Multiprocessor System Detected: 4 CPUs
random: entropy device external interface
kbd0 at kbdmux0
ofwbus0: <Open Firmware Device Tree>
simplebus0: <Flattened device tree simple bus> mem 0x3f000000-0x3fffffff on ofwbus0
generic_timer0: <ARMv7 Generic Timer> irq 10000,10001,10002,10003 on ofwbus0
generic_timer0: Unable to alloc int resource.
device_attach: generic_timer0 attach returned 6
generic_timer0: <ARMv7 Generic Timer> irq 10000,10001,10002,10003 on ofwbus0
device_attach: generic_timer0 attach returned 6
intc0: <BCM2835 Interrupt Controller> mem 0xb200-0xb3ff on simplebus0
bcmwd0: <BCM2708/2835 Watchdog> mem 0x10001c-0x100027 on simplebus0
gpio0: <BCM2708/2835 GPIO controller> mem 0x200000-0x2000af irq 10004,10005,10006,10007 on simplebus0
gpio0: read-only pins: 46,48-53.
gpio0: reserved pins: 48-53.
gpiobus0: <OFW GPIO bus> on gpio0
gpioled0: <GPIO led> at pin 35 on gpiobus0
gpioled1: <GPIO led> at pin 47 on gpiobus0
gpioc0: <GPIO controller> on gpio0
iichb0: <BCM2708/2835 BSC controller> mem 0x205000-0x20501f irq 10008 on simplebus0
iicbus0: <OFW I2C bus> on iichb0
iic0: <I2C generic I/O> on iicbus0
iichb1: <BCM2708/2835 BSC controller> mem 0x804000-0x80401f irq 10009 on simplebus0
iicbus1: <OFW I2C bus> on iichb1
iic1: <I2C generic I/O> on iicbus1
spi0: <BCM2708/2835 SPI controller> mem 0x204000-0x20401f irq 10010 on simplebus0
spibus0: <OFW SPI bus> on spi0
bcm_dma0: <BCM2835 DMA Controller> mem 0x7000-0x7fff,0xe05000-0xe05fff irq 10011,10012,10013,10014,10015,10016,10017,10018,10019,10020,10021,10022,10023 on simplebus0
mbox0: <BCM2835 VideoCore Mailbox> mem 0xb880-0xb8bf irq 10024 on simplebus0
sdhci_bcm0: <Broadcom 2708 SDHCI controller> mem 0x300000-0x3000ff irq 10025 on simplebus0
mmc0: <MMC/SD bus> on sdhci_bcm0
uart0: <PrimeCell UART (PL011)> mem 0x201000-0x201fff irq 10026 on simplebus0
uart0: console (115200,n,8,1)
vchiq0: <BCM2835 VCHIQ> mem 0xb800-0xb84f irq 10027 on simplebus0
vchiq: local ver 8 (min 3), remote ver 8.
pcm0: <VCHIQ audio> on vchiq0
bcm283x_dwcotg0: <DWC OTG 2.0 integrated USB controller (bcm283x)> mem 0x980000-0x99ffff irq 10028 on simplebus0
usbus0 on bcm283x_dwcotg0
cpulist0: <Open Firmware CPU Group> on ofwbus0
cpu0: <Open Firmware CPU> on cpulist0
bcm2835_cpufreq0: <CPU Frequency Control> on cpu0
cpu1: <Open Firmware CPU> on cpulist0
cpu2: <Open Firmware CPU> on cpulist0
cpu3: <Open Firmware CPU> on cpulist0
fb0: <BCM2835 VT framebuffer driver> on ofwbus0
fbd0 on fb0
VT: initialize with new VT driver "fb".
fb0: 1824x984(1824x984 at 0,0) 24bpp
fb0: fbswap: 1, pitch 5472, base 0x3d359000, screen_size 5428224
cryptosoft0: <software crypto>
panic: No usable event timer found!
cpuid = 0
KDB: enter: panic
[ thread pid 0 tid 100000 ]
Stopped at      $d.6:   ldrb    r15, [r15, r15, ror r15]!
db> 

Many thanks if you got this far, and for any guidance. I'm well and truly baffled.

bob prohaska