Greetings,

I got the below dmesg and the first bad commit is

git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
commit 68458dede7e0055198318dcb0318df3b4f419507
CommitDate: Mon Jan 13 14:46:59 2014 -0500

    mwifiex: add USB8897 support
    
[    6.211307] Error: Driver 'usb8xxx' is already registered, aborting...
[    6.211307] Error: Driver 'usb8xxx' is already registered, aborting...
[    6.217261] mwifiex_usb: Driver register failed!
[    6.217261] mwifiex_usb: Driver register failed!

git bisect start 6d0abeca3242a88cab8232e4acd7e2bf088f3bc2 v3.13 --
git bisect  bad e914e3f48d0f3978d1561ae3668908e4c0262acf  # 12:41      7-     17  Merge branch 'for-linus' of git://ftp.arm.linux.org.uk/~rmk/linux-arm
git bisect good 0d90d638720ba14874e34cbd8766e4dc3f14f458  # 12:55     27+     27  Merge tag 'for-f2fs-3.14' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs
git bisect  bad b2e448eca1a52fea181905845728ae00a138d84e  # 12:59      0-      3  Merge branch 'ipmi' (ipmi patches from Corey Minyard)
git bisect good 91466574be1a3701fab4abf5ac1539b556575a81  # 13:04     27+     27  Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/rzhang/linux
git bisect good 7ae0e06b909e31bf9a396a2326ef09b768d9b4c4  # 13:08     27+     27  Merge tag 'arc-v3.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc
git bisect  bad 4ba9920e5e9c0e16b5ed24292d45322907bb9035  # 13:12      1-     15  Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next
git bisect good f6d13daaddeb6e63b15a93bf36a80173bafd29bf  # 13:28     27+     27  Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
git bisect good 82c477669a4665eb4e52030792051e0559ee2a36  # 13:39     27+     27  Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
git bisect good ad86c55bac643a745f480d26689d153ec0f38b04  # 13:45     27+     27  Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-next into for-davem
git bisect good b92ed1688e316d1b4410559272e68b246bdc7d0a  # 13:49     27+     27  Merge branch 'qlcnic'
git bisect good cf84eb0b09c0f09b4c70a648b9dfeec78be61f07  # 13:53     27+     27  Merge branch 'virtio_rx_merging'
git bisect  bad 05d063aa867b7a31b84543400b19f5673afc736c  # 13:58      1-      8  ixgbevf: make use of the dev pointer in the ixgbevf_ring struct
git bisect  bad 0673effd41dba323d6a280ef37b5ef29f3f5a653  # 14:03      4-     11  b43: Fix unload oops if firmware is not available
git bisect good 26b0e411d37a2ca5992d02884dc3fa4e1907e598  # 14:06     27+     27  mac80211_hwsim: restore regulatory testing functionality
git bisect good ec665facde820179d71d0f064e692f449df2b94f  # 14:10     27+     27  Merge tag 'nfc-next-3.14-1' of git://git.kernel.org/pub/scm/linux/kernel/git/sameo/nfc-next
git bisect good 869526b958f59592c46086c11f638824b08d164a  # 14:14     27+     27  ath10k: add trace event for WMI_DEBUG_MESG_EVENTID
git bisect good 4f7b91404cd5da3657a82b00394f4f5dfbff13d6  # 14:20     27+     27  cfg80211: make regulatory_hint() remove REGULATORY_CUSTOM_REG
git bisect  bad b30d49b294fe339719918965594f12eb7967dca0  # 14:23      2-     14  wl12xx: fix tx power setting
git bisect  bad 68458dede7e0055198318dcb0318df3b4f419507  # 14:24      4-     21  mwifiex: add USB8897 support
git bisect good f87f960b2fb802f26ee3b00c19320e57a9c583ff  # 14:29     27+     27  rtlwifi: rtl8192cu: Add new device ID
git bisect  bad d158fc7f36a25e19791d25a55da5623399a2644f  # 14:35      0-      8  Merge tag 'pci-v3.14-fixes-1' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci
git bisect  bad 12f1d94f0c8b256c04cb9b6b5dd989c32e44f11b  # 14:35      0-      9  Add linux-next specific files for 20140220

Thanks,
Fengguang