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

[Christian Gmeiner]

ping

Am Mo., 14. Mai 2018 um 11:32 Uhr schrieb Christian Gmeiner <
christian.gmeiner at gmail.com>:

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

> --
> 2.17.0



-- 
greets
--
Christian Gmeiner, MSc

https://christian-gmeiner.info