lkml.org 
[lkml]   [2016]   [Jun]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 10/10] x86 tsc: enumerate BXT tsc_khz via CPUID
    Date
    From: Len Brown <len.brown@intel.com>

    Hard code the BXT crystal clock (aka ART - Always Running Timer)
    to 19.200 MHz, and use CPUID leaf 0x15 to determine the BXT TSC frequency.

    Use tsc_khz to sanity check BXT cpu_khz,
    which can be erroneous in some configurations.

    Signed-off-by: Bin Gao <bin.gao@intel.com>
    [lenb: simplified]
    Signed-off-by: Len Brown <len.brown@intel.com>
    ---
    arch/x86/kernel/tsc.c | 16 +++++++++++++++-
    1 file changed, 15 insertions(+), 1 deletion(-)

    diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
    index e1496b7..2a952fc 100644
    --- a/arch/x86/kernel/tsc.c
    +++ b/arch/x86/kernel/tsc.c
    @@ -693,7 +693,11 @@ unsigned long native_calibrate_tsc(void)
    switch (boot_cpu_data.x86_model) {
    case 0x4E: /* SKL */
    case 0x5E: /* SKL */
    - crystal_khz = 24000; /* 24 MHz */
    + crystal_khz = 24000; /* 24.0 MHz */
    + break;
    + case 0x5C: /* BXT */
    + crystal_khz = 19200; /* 19.2 MHz */
    + break;
    }
    }

    @@ -895,6 +899,8 @@ int recalibrate_cpu_khz(void)
    tsc_khz = x86_platform.calibrate_tsc();
    if (tsc_khz == 0)
    tsc_khz = cpu_khz;
    + else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz)
    + cpu_khz = tsc_khz;
    cpu_data(0).loops_per_jiffy = cpufreq_scale(cpu_data(0).loops_per_jiffy,
    cpu_khz_old, cpu_khz);

    @@ -1302,8 +1308,16 @@ void __init tsc_init(void)

    cpu_khz = x86_platform.calibrate_cpu();
    tsc_khz = x86_platform.calibrate_tsc();
    +
    + /*
    + * Trust non-zero tsc_khz as authorative,
    + * and use it to sanity check cpu_khz,
    + * which will be off if system timer is off.
    + */
    if (tsc_khz == 0)
    tsc_khz = cpu_khz;
    + else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz)
    + cpu_khz = tsc_khz;

    if (!tsc_khz) {
    mark_tsc_unstable("could not calculate TSC khz");
    --
    2.9.0
    \
     
     \ /
      Last update: 2016-06-17 08:01    [W:2.725 / U:0.284 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site