On Tue, Jun 2, 2015 at 12:33 PM, Thomas Gleixner <t...@linutronix.de> wrote: > On Thu, 21 May 2015, Adrian Hunter wrote: > >> If it takes longer than 12us to read the PIT counter lsb/msb, >> then the error margin will never fall below 500ppm within 50ms, >> and Fast TSC calibration will always fail. > > So finally the legacy PIT emulation takes longer than the 30 years old > hardware implementation. Progress! > >> This patch detects when that will happen and switches to using >> a slightly different algorithm that takes advantage of the PIT's >> latch comand. > > Is there really no smarter way to figure out the TSC frequency on > modern systems?
I just asked Len this question yesterday. intel_pstate can do it, although the algorithm is a bit gross. --Andy > > Thanks, > > tglx -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
