On Mon, 10 Mar 2014, Julian Wollrath wrote:
> on a Thinkpad x121e (AMD E-450 APU) with version 3.13.5 and earlier of
> the kernel I get:
> [...]
> [ 0.000000] tsc: Fast TSC calibration using PIT
> [ 0.001000] tsc: Detected 1646.619 MHz processor
> [ 0.000004] Calibrating delay loop (skipped), value calculated using
> timer frequency.. 3293.23 BogoMIPS (lpj=1646619)
> [...]
>
>
> but starting with v3.14-rc1 the fast TSC calibration fails:
> [...]
> [ 0.000000] tsc: Fast TSC calibration failed
> [ 0.000000] tsc: PIT calibration matches HPET. 1 loops
> [ 0.000000] tsc: Detected 1646.490 MHz processor
> [...]
The only change in the calibration code post 3.13 is that we added the
MSR based calibration for ATOM:
@@ -419,6 +651,13 @@ unsigned long native_calibrate_tsc(void)
unsigned long flags, latch, ms, fast_calibrate;
int hpet = is_hpet_enabled(), i, loopmin;
+ /* Calibrate TSC using MSR for Intel Atom SoCs */
+ local_irq_save(flags);
+ fast_calibrate = try_msr_calibrate_tsc();
+ local_irq_restore(flags);
+ if (fast_calibrate)
+ return fast_calibrate;
+
local_irq_save(flags);
fast_calibrate = quick_pit_calibrate();
local_irq_restore(flags);
And that definitely does not affect the quick calibration. No idea,
except bisecting.
Thanks,
tglx
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