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

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Hi,

On 30-01-2020 17:02, David Laight wrote:
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?

I have no idea. Andy if you can find any docs on the MSR_FSB_FREQ values
for Merriefield (BYT MID) and Moorefield (CHT MID) that would be great,
if not I suggest we stick with what we have.

Regards,

Hans




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