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From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Hans de Goede <hdegoede@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	vipul kumar <vipulk0511@gmail.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	linux-kernel@vger.kernel.org, Stable <stable@vger.kernel.org>,
	Srikanth Krishnakar <Srikanth_Krishnakar@mentor.com>,
	Cedric Hombourger <Cedric_Hombourger@mentor.com>,
	x86@kernel.org, Len Brown <len.brown@intel.com>,
	Vipul Kumar <vipul_kumar@mentor.com>
Subject: Re: [v3] x86/tsc: Unset TSC_KNOWN_FREQ and TSC_RELIABLE flags on Intel Bay Trail SoC
Date: Wed, 29 Jan 2020 16:14:44 +0200	[thread overview]
Message-ID: <20200129141444.GE32742@smile.fi.intel.com> (raw)
In-Reply-To: <0d361322-87aa-af48-492c-e8c4983bb35b@redhat.com>

On Wed, Jan 29, 2020 at 02:21:40PM +0100, Hans de Goede wrote:
> On 29-01-2020 14:03, Andy Shevchenko wrote:
> > On Tue, Jan 28, 2020 at 11:39:28PM +0100, Thomas Gleixner wrote:
> > > Hans de Goede <hdegoede@redhat.com> writes:

...

> > > Typical crystal frequencies are 19.2, 24 and 25Mhz.
> > 
> > Hans, I think Cherrytrail may be affected by this as the others.
> > CHT AFAIK uses 19.2MHz xtal.
> 
> Are you sure?

I'm not. I may mixed this with PMC clock.

> The first 5 entries of the CHT MSR_FSB_FREQ documentation exactly
> match those of the BYT documentation (which has only 5 entries),
> which suggests to me that CHT is also using a 25 MHz crystal.
> 
> I can also make the other CHT only frequencies when assuming a 25
> MHz crystal, here is a bit from the patch I'm working on for this:
> 
> /*
>  * Cherry Trail SDM MSR_FSB_FREQ frequencies to PLL settings map:
>  * 0000:   25 * 20 /  6  =  83.3333 MHz
>  * 0001:   25 *  4 /  1  = 100.0000 MHz
>  * 0010:   25 * 16 /  3  = 133.3333 MHz
>  * 0011:   25 * 28 /  6  = 116.6667 MHz
>  * 0100:   25 * 16 /  5  =  80.0000 MHz
>  * 0101:   25 * 56 / 15  =  93.3333 MHz
>  * 0110:   25 * 18 /  5  =  90.0000 MHz
>  * 0111:   25 * 32 /  9  =  88.8889 MHz
>  * 1000:   25 *  7 /  2  =  87.5000 MHz
>  */
> 
> The only one which is possibly suspicious here is this line:
> 
>  * 0111:   25 * 32 /  9  =  88.8889 MHz
> 
> The SDM says 88.9 MHz for this one.

Anyway it seems need to be fixed as well.

Btw, why we are mentioning 20 / 6 and 28 / 6 when arithmetically
it's the same as 10 / 3 and 14 / 3?

-- 
With Best Regards,
Andy Shevchenko



  reply	other threads:[~2020-01-29 14:14 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-21 14:41 [v3] x86/tsc: Unset TSC_KNOWN_FREQ and TSC_RELIABLE flags on Intel Bay Trail SoC Vipul Kumar
2020-01-21 15:24 ` Andy Shevchenko
2020-01-21 17:45 ` Thomas Gleixner
     [not found]   ` <CADdC98RJpsvu_zWehNGDDN=W11rD11NSPaodg-zuaXsHuOJYTQ@mail.gmail.com>
2020-01-22 14:45     ` Thomas Gleixner
     [not found]       ` <CADdC98TE4oNWZyEsqXzr+zJtfdTTOyeeuHqu1u04X_ktLHo-Hg@mail.gmail.com>
2020-01-23 14:12         ` Thomas Gleixner
2020-01-23 14:41         ` Andy Shevchenko
2020-01-23 21:18           ` Hans de Goede
2020-01-24  8:35             ` Thomas Gleixner
2020-01-24  9:11               ` Hans de Goede
2020-01-24 11:55                 ` Thomas Gleixner
2020-01-24 15:54                   ` Hans de Goede
     [not found]                     ` <CADdC98To8VKOUWnR+8zAJ04vgdc4vJoh2h96588+5XFer9YTJw@mail.gmail.com>
2020-01-28 14:23                       ` Hans de Goede
2020-01-28 14:39                         ` vipul kumar
2020-01-28 15:11                       ` Thomas Gleixner
2020-01-28 18:57                   ` Hans de Goede
2020-01-28 22:39                     ` Thomas Gleixner
2020-01-29 13:03                       ` Andy Shevchenko
2020-01-29 13:21                         ` Hans de Goede
2020-01-29 14:14                           ` Andy Shevchenko [this message]
2020-01-29 14:27                             ` Hans de Goede
2020-01-29 15:13                               ` Thomas Gleixner
2020-01-29 15:53                                 ` Andy Shevchenko
2020-01-29 15:59                                   ` Andy Shevchenko
2020-01-29 16:02                                     ` Andy Shevchenko
2020-01-29 20:57                                   ` Thomas Gleixner
2020-01-30  8:54                                     ` Hans de Goede
2020-02-13 18:32                                     ` Dave Hansen
2020-02-13 21:06                                       ` Thomas Gleixner
2020-01-29 15:14                               ` David Laight
2020-01-29 11:43             ` vipul kumar
2020-01-29  5:20       ` vipul kumar
     [not found] ` <20200122022619.B95C024655@mail.kernel.org>
2020-01-22  4:24   ` Kumar, Vipul

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