• Borislav Petkov's avatar
    x86, tsc: Remove CPU frequency calibration on AMD · acf01734
    Borislav Petkov authored
    6b37f5a2 introduced the CPU frequency
    calibration code for AMD CPUs whose TSCs didn't increment with the
    core's P0 frequency. From F10h, revB onward, however, the TSC increment
    rate is denoted by MSRC001_0015[24] and when this bit is set (which
    should be done by the BIOS) the TSC increments with the P0 frequency
    so the calibration is not needed and booting can be a couple of mcecs
    faster on those machines.
    
    Besides, there should be virtually no machines out there which don't
    have this bit set, therefore this calibration can be safely removed. It
    is a shaky hack anyway since it assumes implicitly that the core is in
    P0 when BIOS hands off to the OS, which might not always be the case.
    Signed-off-by: default avatarBorislav Petkov <borislav.petkov@amd.com>
    LKML-Reference: <20100825162823.GE26438@aftab>
    Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
    acf01734
tsc.c 23 KB