cvs commit: src/sys/dev/uart uart_dev_ns8250.c

Marcel Moolenaar marcel at
Tue Apr 3 01:21:11 UTC 2007

marcel      2007-04-03 01:21:10 UTC

  FreeBSD src repository

  Modified files:
    sys/dev/uart         uart_dev_ns8250.c 
  Don't use a time-limiting loop that's defined in terms of the baudrate
  in the putc() method.  Likewise, in the getc() method, don't check for
  received characters with an interval defined in terms of the baudrate.
  In both cases it works equally well to implement a fixed delay.  More
  importantly, it avoids calculating a delay that's roughly 1/10th the
  time it takes to send/receive a character. The calculation is costly
  and happens for every character sent or received, affecting low-level
  console or debug port performance significantly. Secondly, when the
  RCLK is not available or unreliable, the delays could disrupt normal
  The fixed delay is 1/10th the time it takes to send a character at
  230400 bps.
  Revision  Changes    Path
  1.27      +7 -13     src/sys/dev/uart/uart_dev_ns8250.c

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