[PATCH] Mark TSC on GeodeLX reliable
The Geode can safely use the TSC for highres, since: 1) Does not support frequency scaling, 2) The TSC _does_ count when the CPU is halted. Furthermore, the Geode supports a mode called "suspension on halt", where Suspend mode (which interacts with the power management states) is entered. TSC counting during suspend mode is controlled by bit 8 of the Bus Controller Configuration Register #0 (thanks Tom!). 3) no SMP :) Check if "RTSC counts during suspension" and remove the requirement for verification, so the clocksource code can safely select it as an timesource for the highres timers subsystem. Signed-off-by: Marcelo Tosatti <marcelo@kvack.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: john stultz <johnstul@us.ibm.com> Cc: Roman Zippel <zippel@linux-m68k.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -364,6 +364,25 @@ __cpuinit int unsynchronized_tsc(void)
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return tsc_unstable;
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}
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/*
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* Geode_LX - the OLPC CPU has a possibly a very reliable TSC
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*/
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#ifdef CONFIG_MGEODE_LX
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/* RTSC counts during suspend */
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#define RTSC_SUSP 0x100
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static void __init check_geode_tsc_reliable(void)
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{
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unsigned long val;
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rdmsrl(MSR_GEODE_BUSCONT_CONF0, val);
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if ((val & RTSC_SUSP))
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clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
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}
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#else
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static inline void check_geode_tsc_reliable(void) { }
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#endif
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static int __init init_tsc_clocksource(void)
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{
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@ -372,6 +391,7 @@ static int __init init_tsc_clocksource(void)
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dmi_check_system(bad_tsc_dmi_table);
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unsynchronized_tsc();
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check_geode_tsc_reliable();
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current_tsc_khz = tsc_khz;
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clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
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clocksource_tsc.shift);
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@ -307,4 +307,7 @@ static inline void wrmsrl (unsigned long msr, unsigned long long val)
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#define MSR_CORE_PERF_GLOBAL_CTRL 0x38f
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#define MSR_CORE_PERF_GLOBAL_OVF_CTRL 0x390
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/* Geode defined MSRs */
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#define MSR_GEODE_BUSCONT_CONF0 0x1900
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#endif /* __ASM_MSR_H */
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