[U-Boot] [PATCH] x86: tsc: add support for reading CPU freq from cpuid

[Bin Meng]

On Mon, May 14, 2018 at 5:32 PM, Christian Gmeiner
<christian.gmeiner at gmail.com> wrote:
> Starting with cpuid level 0x16 (Skylake-based processors)
> it is possible to get CPU base freq via cpuid.
>
> This fixes booting on a skylake based system.
>
> Signed-off-by: Christian Gmeiner <christian.gmeiner at gmail.com>
> ---
>  drivers/timer/tsc_timer.c | 31 +++++++++++++++++++++++++------
>  1 file changed, 25 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/timer/tsc_timer.c b/drivers/timer/tsc_timer.c
> index c7fefd2031..96a3e55513 100644
> --- a/drivers/timer/tsc_timer.c
> +++ b/drivers/timer/tsc_timer.c
> @@ -21,6 +21,17 @@
>
>  DECLARE_GLOBAL_DATA_PTR;
>
> +static unsigned long cpu_mhz_from_cpuid(void)
> +{
> +       if (gd->arch.x86_vendor != X86_VENDOR_INTEL)
> +               return 0;
> +
> +       if (cpuid_eax(0) < 0x16)
> +               return 0;
> +
> +       return cpuid_eax(0x16);
> +}
> +
>  /*
>   * According to Intel 64 and IA-32 System Programming Guide,
>   * if MSR_PERF_STAT[31] is set, the maximum resolved bus ratio can be
> @@ -343,14 +354,22 @@ static void tsc_timer_ensure_setup(void)
>         if (!gd->arch.clock_rate) {
>                 unsigned long fast_calibrate;
>
> +               fast_calibrate = cpu_mhz_from_cpuid();
> +               if (fast_calibrate)
> +                       goto done;
> +
>                 fast_calibrate = cpu_mhz_from_msr();
> -               if (!fast_calibrate) {
> -                       fast_calibrate = quick_pit_calibrate();
> -                       if (!fast_calibrate)
> -                               panic("TSC frequency is ZERO");
> -               }
> +               if (fast_calibrate)
> +                       goto done;
> +
> +               fast_calibrate = quick_pit_calibrate();
> +               if (fast_calibrate)
> +                       goto done;
> +
> +               panic("TSC frequency is ZERO");
>
> -               gd->arch.clock_rate = fast_calibrate * 1000000;
> +               done:

nits: this indention is wrong, and will cause checkpatch warnings.

> +                       gd->arch.clock_rate = fast_calibrate * 1000000;
>         }
>  }

Reviewed-by: Bin Meng <bmeng.cn at gmail.com>

I can fix the nits when applying.

Regards,
Bin