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Commit 07190a08 authored by Marcelo Tosatti's avatar Marcelo Tosatti Committed by Linus Torvalds
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[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: default avatarMarcelo Tosatti <marcelo@kvack.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5d8b34fd

arch/i386/kernel/tsc.c

+20 −0
Original line number Diff line number Diff line
@@ -364,6 +364,25 @@ __cpuinit int unsynchronized_tsc(void) 
	return tsc_unstable;

}



/*

 * Geode_LX - the OLPC CPU has a possibly a very reliable TSC

 */

#ifdef CONFIG_MGEODE_LX

/* RTSC counts during suspend */

#define RTSC_SUSP 0x100



static void __init check_geode_tsc_reliable(void)

{

	unsigned long val;



	rdmsrl(MSR_GEODE_BUSCONT_CONF0, val);

	if ((val & RTSC_SUSP))

		clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;

}

#else

static inline void check_geode_tsc_reliable(void) { }

#endif



static int __init init_tsc_clocksource(void)

{
@@ -372,6 +391,7 @@ static int __init init_tsc_clocksource(void) 
		dmi_check_system(bad_tsc_dmi_table);



		unsynchronized_tsc();

		check_geode_tsc_reliable();

		current_tsc_khz = tsc_khz;

		clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,

							clocksource_tsc.shift);

include/asm-i386/msr.h

+3 −0
Original line number Diff line number Diff line
@@ -307,4 +307,7 @@ static inline void wrmsrl (unsigned long msr, unsigned long long val) 
#define MSR_CORE_PERF_GLOBAL_CTRL	0x38f

#define MSR_CORE_PERF_GLOBAL_OVF_CTRL	0x390



/* Geode defined MSRs */

#define MSR_GEODE_BUSCONT_CONF0         0x1900



#endif /* __ASM_MSR_H */