• Andrew Morton's avatar
    [PATCH] ACPI PM timer · ad77865c
    Andrew Morton authored
    From: Dominik Brodowski <linux@dominikbrodowski.de>,
          John Stultz <johnstul@us.ibm.com>,
          Dmitry Torokhov
    
    Add the ACPI Powermanagement Timer as x86 kernel timing source.  Unlike the
    Time Stamp Counter, it is a reliable timing source which does not get
    affected by aggressive powermanagement features like CPU frequency scaling.
    
    Some ideas and some code are based on Arjan van de Ven's implementation for
    2.4, and on R.  Byron Moore's drivers/acpi/hardware/hwtimer.c.
    
    
    We also replace the loop based delay_pmtmr with a TSC based delay_pmtmr,
    which resolves a number of issues caused by the loop based delay.  Unsynced
    TSCs as well frequency changing TSCs will effect the length of __delay(), but
    it seems this method works best.
    ad77865c
timer_cyclone.c 6.62 KB