Re: [v3] x86/tsc: Unset TSC_KNOWN_FREQ and TSC_RELIABLE flags on Intel Bay Trail SoC

[Hans de Goede]

Hi,

On 1/24/20 9:35 AM, Thomas Gleixner wrote:
> Hans,
>
> Hans de Goede <hdegoede@xxxxxxxxxx> writes:
>
> > Hi,
> >
> > Sorry for top posting, but this is a long and almost unreadable thread ...
> >
> > So it seems to me that a better fix would be to change the freq_desc_byt struct from:
> >
> > static const struct freq_desc freq_desc_byt = {
> >           1, { 83300, 100000, 133300, 116700, 80000, 0, 0, 0 }
> > };
> >
> > to:
> >
> > static const struct freq_desc freq_desc_byt = {
> >           1, { 83333, 100000, 133300, 116700, 80000, 0, 0, 0 }
> > };
> >
> > That should give us the right TSC frequency without needing to mess with
> > the TSC_KNOWN_FREQ and TSC_RELIABLE flags.
>
> Where does that number come from? Just math?

Yes just math, but perhaps the Intel folks can see if they can find some
datasheet to back this up ?

I mean if the calculated freq is off by that much, then chances are that
my solution actuallly is not only "just math" but also correct :)

Regards,

Hans