linux-kernel - Re: [PATCH 2/2 v2] x86/tsc: Add additional Intel CPU models to crystal

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Date:   Wed, 28 Sep 2016 11:00:36 -0400
From:   Len Brown <lenb@...nel.org>
To:     Prarit Bhargava <prarit@...hat.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
        Rafael Aquini <aquini@...hat.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Len Brown <len.brown@...el.com>
Subject: Re: [PATCH 2/2 v2] x86/tsc: Add additional Intel CPU models to
 crystal_khz whitelist

On Mon, Sep 19, 2016 at 8:51 AM, Prarit Bhargava <prarit@...hat.com> wrote:
> In commit aa297292d708 ("x86/tsc: Enumerate SKL cpu_khz and tsc_khz via
> CPUID"), the kernel added support for Intel processors which had
> a different CPU base-frequency and TSC frequency.
>
> The turbostat utility has been updated with KBL and SKX processors,
> and they should also be added to the crystal_khz white list.
>
> For example, on INTEL_FAM6_KABYLAKE_MOBILE native_calibrate_tsc() returns 0 MHz
> for tsc_khz and after this patch native_calibrate_tsc() returns 1608 MHz.
>
> v2: peterz, fix typo for SKX should be 25000
>
> Signed-off-by: Prarit Bhargava <prarit@...hat.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: x86@...nel.org
> Cc: Rafael Aquini <aquini@...hat.com>
> Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Len Brown <len.brown@...el.com>
> Cc: lenb@...nel.org
> ---
>  arch/x86/kernel/tsc.c |    7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
> index 2344758ba8a3..cd0c9ece25de 100644
> --- a/arch/x86/kernel/tsc.c
> +++ b/arch/x86/kernel/tsc.c
> @@ -689,11 +689,18 @@ unsigned long native_calibrate_tsc(void)
>                 switch (boot_cpu_data.x86_model) {
>                 case INTEL_FAM6_SKYLAKE_MOBILE:
>                 case INTEL_FAM6_SKYLAKE_DESKTOP:
> +               case INTEL_FAM6_KABYLAKE_MOBILE:
> +               case INTEL_FAM6_KABYLAKE_DESKTOP:
>                         crystal_khz = 24000;    /* 24.0 MHz */
>                         break;
> +               case INTEL_FAM6_SKYLAKE_X:
> +                       crystal_khz = 25000;    /* 25.0 MHz */
> +                       break;
>                 case INTEL_FAM6_ATOM_GOLDMONT:
>                         crystal_khz = 19200;    /* 19.2 MHz */
>                         break;
> +               default:
> +                       crystal_khz = 0;
>                 }


Correct.

Reviewed-by: Len Brown <len.brown@...el.com>