Broadcom Corp. BCM5880 Secure Applications Processor eats too much power

$ lsusb
Bus 004 Device 004: ID 0a5c:5800 Broadcom Corp. BCM5880 Secure Applications Processor

$ sudo powertop
Power est. Usage Events/s Kategorie Popis
  24.3 W 100,0% Device USB device: 5880 (Broadcom Corp)

On my Dell Latitude E6540 I constantly see this USB device eating about 20 W of power (and I don't see a reason for this kind of device to take that much power). And yes, the fan is always running, even when the computer is completely idle.

The computer has no fingerprint reader (though it was an optional accessory, so the chip is IMHO built to support it). I use the integrated smartcard reader (also handled by this chip). I've set up PAM and LightDM to support smartcard login. However, the power usage is the same regardless of whether a smartcard is inserted or not. I do not intentionally use the integrated TPM chip in any way.

I faced this problem also on Ubuntu 14.04.3 with 3.19 kernel.

Eventually, this could also be a bug in powertop, but the fan almost never stops (even with display backlight to minimum), so I think powertop could be correct.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: linux-image-4.2.0-27-generic 4.2.0-27.32~14.04.1
ProcVersionSignature: Ubuntu 4.2.0-27.32~14.04.1-generic 4.2.8-ckt1
Uname: Linux 4.2.0-27-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.19
Architecture: amd64
CurrentDesktop: Unity
Date: Sat Feb 20 15:33:49 2016
InstallationDate: Installed on 2013-11-05 (837 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
SourcePackage: linux-lts-wily
UpgradeStatus: Upgraded to trusty on 2014-04-12 (678 days ago)
---
ApportVersion: 2.14.1-0ubuntu3.19
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: peci1 2919 F.... pulseaudio
 /dev/snd/pcmC1D0p: peci1 2919 F...m pulseaudio
 /dev/snd/controlC1: peci1 2919 F.... pulseaudio
CurrentDesktop: Unity
DistroRelease: Ubuntu 14.04
HibernationDevice: RESUME=UUID=05314bb8-8590-474c-8af1-1c90dd3bb89c
InstallationDate: Installed on 2013-11-05 (853 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
MachineType: Dell Inc. Latitude E6540
Package: linux (not installed)
ProcFB:
 0 inteldrmfb
 1 radeondrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.2.0-30-generic root=UUID=501ffea4-2b36-441b-a8ca-34805170c396 ro i8042.nopnp quiet splash radeon.modeset=1 radeon.dpm=1 i915.modeset=1 radeon.runpm=0 vt.handoff=7
ProcVersionSignature: Ubuntu 4.2.0-30.36~14.04.1-generic 4.2.8-ckt3
RelatedPackageVersions:
 linux-restricted-modules-4.2.0-30-generic N/A
 linux-backports-modules-4.2.0-30-generic N/A
 linux-firmware 1.127.20
Tags: trusty
Uname: Linux 4.2.0-30-generic x86_64
UpgradeStatus: Upgraded to trusty on 2014-04-12 (695 days ago)
UserGroups: adm autosshfs cdrom dip lpadmin plugdev sambashare sudo video
_MarkForUpload: True
dmi.bios.date: 09/01/2015
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A16
dmi.board.name: 0CYT5F
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 9
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA16:bd09/01/2015:svnDellInc.:pnLatitudeE6540:pvr00:rvnDellInc.:rn0CYT5F:rvrA00:cvnDellInc.:ct9:cvr:
dmi.product.name: Latitude E6540
dmi.product.version: 00
dmi.sys.vendor: Dell Inc.