1. 08 Feb, 2017 5 commits
  2. 06 Feb, 2017 3 commits
  3. 31 Jan, 2017 6 commits
  4. 26 Jan, 2017 3 commits
  5. 25 Jan, 2017 1 commit
    • Johan Hovold's avatar
      USB: serial: ftdi_sio: fix extreme low-latency setting · c6dce262
      Johan Hovold authored
      Since commit 557aaa7f ("ft232: support the ASYNC_LOW_LATENCY
      flag") the FTDI driver has been using a receive latency-timer value of
      1 ms instead of the device default of 16 ms.
      
      The latency timer is used to periodically empty a non-full receive
      buffer, but a status header is always sent when the timer expires
      including when the buffer is empty. This means that a two-byte bulk
      message is received every millisecond also for an otherwise idle port as
      long as it is open.
      
      Let's restore the pre-2009 behaviour which reduces the rate of the
      status messages to 1/16th (e.g. interrupt frequency drops from 1 kHz to
      62.5 Hz) by not setting ASYNC_LOW_LATENCY by default.
      
      Anyone willing to pay the price for the minimum-latency behaviour should
      set the flag explicitly instead using the TIOCSSERIAL ioctl or a tool
      such as setserial (e.g. setserial /dev/ttyUSB0 low_latency).
      
      Note that since commit 0cbd81a9 ("USB: ftdi_sio: remove
      tty->low_latency") the ASYNC_LOW_LATENCY flag has no other effects but
      to set a minimal latency timer.
      Reported-by: default avatarAntoine Aubert <a.aubert@overkiz.com>
      Fixes: 557aaa7f ("ft232: support the ASYNC_LOW_LATENCY flag")
      Cc: stable@vger.kernel.org # v2.6.31: e3e574adSigned-off-by: default avatarJohan Hovold <johan@kernel.org>
      c6dce262
  6. 16 Jan, 2017 22 commits