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

[Christian Gmeiner]

Am Mi., 23. Mai 2018 um 11:48 Uhr schrieb Bin Meng <bmeng.cn at gmail.com>:

> 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.

Oops.

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

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

> I can fix the nits when applying.


That would be great - thanks!
-- 
greets
--
Christian Gmeiner, MSc

https://christian-gmeiner.info