linux-kernel - Re: [v3] x86/tsc: Unset TSC_KNOWN_FREQ and TSC

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Message-ID: <87iml11ccf.fsf@nanos.tec.linutronix.de>
Date:   Fri, 24 Jan 2020 09:35:12 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Hans de Goede <hdegoede@...hat.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        vipul kumar <vipulk0511@...il.com>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        linux-kernel@...r.kernel.org, Stable <stable@...r.kernel.org>,
        Srikanth Krishnakar <Srikanth_Krishnakar@...tor.com>,
        Cedric Hombourger <Cedric_Hombourger@...tor.com>,
        x86@...nel.org, Len Brown <len.brown@...el.com>,
        Vipul Kumar <vipul_kumar@...tor.com>
Subject: Re: [v3] x86/tsc: Unset TSC_KNOWN_FREQ and TSC_RELIABLE flags on Intel Bay Trail SoC

Hans,

Hans de Goede <hdegoede@...hat.com> 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?

Thanks,

        tglx