龍芯派如何使用pwm

官方內核是不是沒有pwm driver。
自己重新編譯，選了pwm，好像還是無效

Python 2.7.8 (default, Nov 30 2017, 16:32:35) 
[GCC 4.9.3 20150626 (Red Hat 4.9.3-7)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from periphery import PWM
>>> pwm=PWM(3,23)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/site-packages/periphery/pwm.py", line 44, in __init__
    self._open(channel, pin)
  File "/usr/lib/python2.7/site-packages/periphery/pwm.py", line 63, in _open
    raise ValueError("PWM channel does not exist, check that the required modules are loaded.")
ValueError: PWM channel does not exist, check that the required modules are loaded.