lkml.org 
[lkml]   [2007]   [May]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH] [7/30] x86_64: Avoid overflows during apic timer calibration
    Date

    From: David P. Reed <dpreed@reed.com>

    - Use 64bit TSC calculations to avoid handling overflow
    - Use 32bit unsigned arithmetic for the APIC timer. This
    way overflows are handled correctly.
    - Fix exit check of loop to account for apic timer counting down

    Signed-off-by: dpreed@reed.com
    Signed-off-by: Andi Kleen <ak@suse.de>

    ---
    arch/x86_64/kernel/apic.c | 11 ++++++-----
    1 file changed, 6 insertions(+), 5 deletions(-)

    Index: linux/arch/x86_64/kernel/apic.c
    ===================================================================
    --- linux.orig/arch/x86_64/kernel/apic.c
    +++ linux/arch/x86_64/kernel/apic.c
    @@ -839,14 +839,15 @@ static void setup_APIC_timer(unsigned in

    static int __init calibrate_APIC_clock(void)
    {
    - int apic, apic_start, tsc, tsc_start;
    + unsigned apic, apic_start;
    + unsigned long tsc, tsc_start;
    int result;
    /*
    * Put whatever arbitrary (but long enough) timeout
    * value into the APIC clock, we just want to get the
    * counter running for calibration.
    */
    - __setup_APIC_LVTT(1000000000);
    + __setup_APIC_LVTT(4000000000);

    apic_start = apic_read(APIC_TMCCT);
    #ifdef CONFIG_X86_PM_TIMER
    @@ -857,13 +858,13 @@ static int __init calibrate_APIC_clock(v
    } else
    #endif
    {
    - rdtscl(tsc_start);
    + rdtscll(tsc_start);

    do {
    apic = apic_read(APIC_TMCCT);
    - rdtscl(tsc);
    + rdtscll(tsc);
    } while ((tsc - tsc_start) < TICK_COUNT &&
    - (apic - apic_start) < TICK_COUNT);
    + (apic_start - apic) < TICK_COUNT);

    result = (apic_start - apic) * 1000L * tsc_khz /
    (tsc - tsc_start);
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/
    \
     
     \ /
      Last update: 2007-05-01 06:07    [W:0.019 / U:0.068 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site