1. 17 3月, 2009 3 次提交
    • L
      Fast TSC calibration: calculate proper frequency error bounds · 9e8912e0
      Linus Torvalds 提交于
      In order for ntpd to correctly synchronize the clocks, the frequency of
      the system clock must not be off by more than 500 ppm (or, put another
      way, 1:2000), or ntpd will end up giving up on trying to synchronize
      properly, and ends up reseting the clock in jumps instead.
      
      The fast TSC PIT calibration sometimes failed this test - it was
      assuming that the PIT reads always took about one microsecond each (2us
      for the two reads to get a 16-bit timer), and that calibrating TSC to
      the PIT over 15ms should thus be sufficient to get much closer than
      500ppm (max 2us error on both sides giving 4us over 15ms: a 270 ppm
      error value).
      
      However, that assumption does not always hold: apparently some hardware
      is either very much slower at reading the PIT registers, or there was
      other noise causing at least one machine to get 700+ ppm errors.
      
      So instead of using a fixed 15ms timing loop, this changes the fast PIT
      calibration to read the TSC delta over the individual PIT timer reads,
      and use the result to calculate the error bars on the PIT read timing
      properly.  We then successfully calibrate the TSC only if the maximum
      error bars fall below 500ppm.
      
      In the process, we also relax the timing to allow up to 25ms for the
      calibration, although it can happen much faster depending on hardware.
      Reported-and-tested-by: NJesper Krogh <jesper@krogh.cc>
      Cc: john stultz <johnstul@us.ibm.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Acked-by: NIngo Molnar <mingo@elte.hu>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      9e8912e0
    • L
      Fix potential fast PIT TSC calibration startup glitch · a6a80e1d
      Linus Torvalds 提交于
      During bootup, when we reprogram the PIT (programmable interval timer)
      to start counting down from 0xffff in order to use it for the fast TSC
      calibration, we should also make sure to delay a bit afterwards to allow
      the PIT hardware to actually start counting with the new value.
      
      That will happens at the next CLK pulse (1.193182 MHz), so the easiest
      way to do that is to just wait at least one microsecond after
      programming the new PIT counter value.  We do that by just reading the
      counter value back once - which will take about 2us on PC hardware.
      Reported-and-tested-by: Njohn stultz <johnstul@us.ibm.com>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a6a80e1d
    • L
      Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6 · 19695ec0
      Linus Torvalds 提交于
      * 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6:
        acpi-wmi: unsigned cannot be less than 0
        thinkpad-acpi: fix module autoloading for older models
        acer-wmi: Unmark as 'experimental'
        acpi-wmi: Unmark as 'experimental'
        acer-wmi: double free in acer_rfkill_exit()
        platform/x86: depends instead of select for laptop platform drivers
        asus-laptop: use select instead of depends on
        eeepc-laptop: restore acpi_generate_proc_event()
        asus-laptop: restore acpi_generate_proc_event()
        acpi: check for pxm_to_node_map overflow
        ACPI: remove doubled status checking
        ACPI suspend: Blacklist Toshiba Satellite L300 that requires to set SCI_EN directly on resume
        Revert "ACPI: make some IO ports off-limits to AML"
        suspend: switch the Asus Pundit P1-AH2 to old ACPI sleep ordering
      19695ec0
  2. 16 3月, 2009 22 次提交
  3. 15 3月, 2009 15 次提交