can detect board with st-util, but can't connect board with openocd

As title says, I can detect my STM32F401-Nucleo board with st-utils from stlink, but can't connect board with openocd. I don't know whether I need to config others or not.

1.Setup stlink v2, and I can detect my STM32F401-Nucleo as below:

➜  bin st-util
2016-03-05T22:20:04 INFO src/stlink-common.c: Loading device parameters....
2016-03-05T22:20:04 INFO src/stlink-common.c: Device connected is: F4 device (Dynamic Efficency), id 0x10006433
2016-03-05T22:20:04 INFO src/stlink-common.c: SRAM size: 0x18000 bytes (96 KiB), Flash: 0x80000 bytes (512 KiB) in pages of 16384 bytes
2016-03-05T22:20:04 INFO gdbserver/gdb-server.c: Chip ID is 00000433, Core ID is  2ba01477.
2016-03-05T22:20:04 INFO gdbserver/gdb-server.c: Target voltage is 3265 mV.
2016-03-05T22:20:04 INFO gdbserver/gdb-server.c: Listening at *:4242...

2.but I can't connect my board with openocd, error is below:

➜  bin pwd
/Applications/GNU ARM Eclipse/OpenOCD/0.10.0-201601101000-dev/bin
➜  bin ./openocd -f board/stm32f4discovery.cfg
GNU ARM Eclipse 64-bits Open On-Chip Debugger 0.10.0-dev-00287-g85cec24 (2016-01-10-12:03)
Licensed under GNU GPL v2
For bug reports, read
    http://openocd.org/doc/doxygen/bugs.html
Info : The selected transport took over low-level target control. The results might differ compared to plain JTAG/SWD
adapter speed: 2000 kHz
adapter_nsrst_delay: 100
none separate
srst_only separate srst_nogate srst_open_drain connect_deassert_srst
Info : Unable to match requested speed 2000 kHz, using 1800 kHz
Info : Unable to match requested speed 2000 kHz, using 1800 kHz
Info : clock speed 1800 kHz
Error: open failed
in procedure 'init'
in procedure 'ocd_bouncer'

➜  bin

my Dev-environment is:

Board : STM32F401RE Nucleo
OS X EI Caption : 10.11 (15A284)
iTerm2 : Build 2.1.4
OpenOCD : 0.10.0-201601101000-dev
ST-Link V2 : https://github.com/texane/stlink

ilg-archived / openocd

can detect board with st-util, but can't connect board with openocd #7