RE: [PATCH 3/3] x86/tsc_msr: Make MSR derived TSC frequency more accurate

[David Laight]

From: Hans de Goede
> Sent: 30 January 2020 15:55
...
> >> + * Moorefield (CHT MID) SDM MSR_FSB_FREQ frequencies simplified PLL model:
> >> + * 0000:   100 *  5 /  6  =  83.3333 MHz
> >> + * 0001:   100 *  1 /  1  = 100.0000 MHz
> >> + * 0010:   100 *  4 /  3  = 133.3333 MHz
> >> + * 0011:   100 *  1 /  1  = 100.0000 MHz
> >
> > Unless I'm going cross-eyed, that's 4 times the exact same table.
> 
> Correct, except that the not listed values on the none Cherry Trail
> table are undefined in the SDM, so we should probably deny them
> (or as the old code was doing simply return 0).
> 
> And at least the Moorefield (CHT MID) table is different for 0011, that
> is again 100 MHz like 0001 instead of 116.6667 as it is for BYT and CHT.
> 
> Note that the Merriefield (BYT MID) and Moorefield (CHT MID) values are
> based on the old code I've not seen those values in the current latest
> version of the SDM.

I wonder if Moorefield:11 is an old typo?

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)