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Date: Tue, 2 Jun 2015 21:33:25 +0200 (CEST) From: Thomas Gleixner <tglx@...utronix.de> To: Adrian Hunter <adrian.hunter@...el.com> cc: LKML <linux-kernel@...r.kernel.org>, Andy Lutomirski <luto@...capital.net>, Linus Torvalds <torvalds@...ux-foundation.org>, Andi Kleen <ak@...ux.intel.com>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, Len Brown <lenb@...nel.org> Subject: Re: [PATCH RFC] x86, tsc: Allow for high latency in quick_pit_calibrate() 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? Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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