Loading CAN cape on startup

Using the new Debian builds on my beaglebone white, I'm trying to load a
device tree overlay for the CAN cape on startup, but it seems to fail to
load automatically (but try), however, I can load the device tree overlay
manually and it seems to work just fine. What am I doing wrong?

I even tried putting the following entry in uEnv.txt:

optargs=capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN,BB-BONE-EMMC-2G
capemgr.enable_partno=BB-BONE-SERL-01

I don't know of any hardware conflicts, and the same hardware works fine on
Angstrom. I really want to migrate to Debian for several reasons.

Here's the command and successful load manually:

debian [ at ] arm:~$ sudo sh -c "echo BB-BONE-SERL-01 >
/sys/devices/bone_capemgr.8/slots"
[sudo] password for debian:
[ 99.355373] bone-capemgr bone_capemgr.8: part_number 'BB-BONE-SERL-01',
version 'N/A'
[ 99.365522] bone-capemgr bone_capemgr.8: slot #5: generic override
[ 99.372251] bone-capemgr bone_capemgr.8: bone: Using override eeprom
data at slot 5
[ 99.380404] bone-capemgr bone_capemgr.8: slot #5: 'Override Board
Name,00A0,Override Manuf,BB-BONE-SERL-01'
[ 99.391261] bone-capemgr bone_capemgr.8: slot #5: Requesting part
number/version based 'BB-BONE-SERL-01-00A0.dtbo
[ 99.402199] bone-capemgr bone_capemgr.8: slot #5: Requesting firmware
'BB-BONE-SERL-01-00A0.dtbo' for board-name 'Override Board Name', version
'00A0'
[ 99.434783] bone-capemgr bone_capemgr.8: slot #5: dtbo
'BB-BONE-SERL-01-00A0.dtbo' loaded; converting to live tree
[ 99.448201] bone-capemgr bone_capemgr.8: slot #5: #2 overlays
[ 99.456729] platform 481d0000.d_can: alias fck already exists
[ 99.468434] bone-capemgr bone_capemgr.8: slot #5: Applied #2 overlays.
debian [ at ] arm:~$ [ 99.538154] CAN device driver interface
[ 99.562768] c_can_platform 481d0000.d_can: invalid resource
[ 99.568915] c_can_platform 481d0000.d_can: control memory is not used
for raminit
[ 99.580927] c_can_platform 481d0000.d_can: c_can_platform device
registered (regs=fa1d0000, irq=71)

debian [ at ] arm:~$ cat /sys/devices/bone_capemgr.8/slots
1: 55:PF---
2: 56:PF---
3: 57:PF---
5: ff:P-O-L Override Board Name,00A0,Override Manuf,BB-BONE-SERL-01
debian [ at ] arm:~$ sudo ip link set can0 type can bitrate 50000
debian [ at ] arm:~$ sudo ifconfig can0 up
[ 248.574278] c_can_platform 481d0000.d_can can0: setting BTR=1c1d
BRPE=0000
debian [ at ] arm:~$ candump can0

Also, what is getting "overridden" and making the slots claim "Override
Board Name,00A0,Override Manuf" etc?

-Andrew