Commit 4635fdc6 authored by Bin Gao's avatar Bin Gao Committed by Thomas Gleixner

x86/tsc: Mark Intel ATOM_GOLDMONT TSC reliable

On Intel GOLDMONT Atom SoC TSC is the only available clocksource, so there
is no way to do software calibration or have a watchdog clocksource for it.
Software calibration is already disabled via the TSC_KNOWN_FREQ flag, but
the watchdog requirement still persists, so such systems cannot switch to
high resolution/nohz mode.

Mark it reliable, so it becomes usable. Hardware teams confirmed that this
is safe on that SoC.
Signed-off-by: default avatarBin Gao <bin.gao@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1479241644-234277-4-git-send-email-bin.gao@linux.intel.comSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 4ca4df0b
...@@ -709,6 +709,13 @@ unsigned long native_calibrate_tsc(void) ...@@ -709,6 +709,13 @@ unsigned long native_calibrate_tsc(void)
*/ */
setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
/*
* For Atom SoCs TSC is the only reliable clocksource.
* Mark TSC reliable so no watchdog on it.
*/
if (boot_cpu_data.x86_model == INTEL_FAM6_ATOM_GOLDMONT)
setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
return crystal_khz * ebx_numerator / eax_denominator; return crystal_khz * ebx_numerator / eax_denominator;
} }
......
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